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Neurology_Adams. Walsh KW: Neuropsychology: A Clinical Approach, 3rd ed. New York, Churchill Livingstone, 1994. Weinberger LM, Grant FC: Visual hallucinations and their neuro-optical correlates. Arch Ophthalmol 23:166, 1941. Weintraub S, Mesulam M-M: Right cerebral dominance in spatial attention. Arch Neurol 44:621, 1987. Weiskrantz L, Warrington EK, Saunders MD, et al: Visual capacity in the blind field following a restricted occipital ablation. Brain 97:709, 1974. Williams W: Temporal lobe syndromes. In: Vinken PJ, Bruyn GW (eds): Handbook of Clinical Neurology, Vol. 2. Amsterdam, North-Holland, 1969, pp 700–724. Wolpert I: Die Simultanagnosie-Storung der Gesamtauffassung. Z Gesamte Neurol Psychiatr 93:397, 1924. Yakovlev PI: Motility, behavior, and the brain: Stereodynamic organization and neural co-ordinates of behavior. J Nerv Ment Dis 107:313, 1948. Zatorre RJ, Evans AC, Meyer E: Neural mechanisms underlying melodic perception and memory for pitch. J Neurosci 14:1908, 1994.


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Neurology_Adams. Zatorre RJ, Evans AC, Meyer E: Neural mechanisms underlying melodic perception and memory for pitch. J Neurosci 14:1908, 1994. Figure 21-1. Photograph of the lateral surface of the human brain. (Reproduced by permission from Carpenter MB, Sutin J: Human Neuroanatomy, 8th ed. Baltimore, Williams & Wilkins, 1982.) Figure 21-2. Cytoarchitectural zones of the human cerebral cortex according to Brodmann. A. Lateral surface. B. Medial surface. C. Basal inferior surface. The functional zones of the cortex are illustrated in Fig. 21-3.


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Neurology_Adams. Figure 21-3. A and B. Approximate distribution of functional zones on lateral (A) and medial (B) aspects of the cerebral cortex. Abbreviations: A1, primary auditory cortex; AA, auditory association cortex; AG, angular gyrus; CG, cingulate cortex; IPL, inferior parietal lobule; IT, inferior temporal gyrus; M1, primary motor area; MA, motor association cortex; MPO, medial parietooccipital area; MT, middle temporal gyrus; OF, orbitofrontal region; PC, prefrontal cortex; PH, parahippocampal region; PO, parolfactory area; PS, peristriate cortex; RS, retrosplenial area; S1, primary somatosensory area; SA, somatosensory association cortex; SG, supramarginal gyrus; SPL, superior parietal lobule; ST, superior temporal gyrus; TP, temporopolar cortex; V1, primary visual cortex; VA, visual association cortex. (Redrawn by permission from M-M Mesulam.)


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Neurology_Adams. Figure 21-4. The basic cytoarchitecture of the cerebral cortex, adapted from Brodmann. The six basic cell layers are indicated on the left, and the fiber layers on the right (see text). Figure 21-5. Four fundamental types of cerebral cortex and their distribution in the cerebrum. The primary visual cortex has a preponderance of small neurons; hence, it was historically called “granular.” The primary motor cortex, by contrast, has relatively fewer small neurons and was described as “agranular.” (Reproduced with permission from Kandel ER, Schwartz JH, Jessel TM: Principles of Neural Science, 4th ed. New York, McGraw-Hill, 2000.)


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Neurology_Adams. Principles of Neural Science, 4th ed. New York, McGraw-Hill, 2000.) Figure 21-6. Connections involved in naming a seen object and in reading. The visual pattern is transferred from the visual cortex and association areas to the angular gyrus, which arouses the auditory pattern in the Wernicke area. The auditory pattern is transmitted to the Broca area through the arcuate fasciculus, where the articulatory form is aroused and transferred to the contiguous face area of the motor cortex. With destruction of the left visual cortex and splenium (or intervening white matter), the words perceived in the right visual cortex cannot cross over to the language areas and the patient cannot read. Chapter 21 Neurologic Disorders Caused by Lesions in Specific Parts of the Cerebrum Disorders of Speech and Language


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Neurology_Adams. Chapter 21 Neurologic Disorders Caused by Lesions in Specific Parts of the Cerebrum Disorders of Speech and Language Speech and language functions are of fundamental human significance, both in social interaction and in private intellectual life. When they are disturbed as a consequence of brain disease, the functional loss exceeds in many ways all others in gravity—even blindness, deafness, and paralysis. The neurologist is concerned with all derangements of speech and language, including those of reading and writing because they are almost invariably manifestations of disease of the brain.


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Neurology_Adams. Viewed broadly, language is the means of symbolic representation of objects, actions, and events and, therefore, the mirror of all higher mental activity. The internal manipulation of these symbols constitutes thinking and their retention is the substance of memory. In a narrower context, language is the means whereby patients communicate their complaints and problems to the physician and at the same time, the medium for all delicate interpersonal transactions. Consequently, any disease process that interferes with speech or the understanding of spoken words touches the very core of the physician–patient relationship. Finally, the study of language disorders and the development of language (see Chap. 27) serve to illuminate the relationship between psychologic functions and the anatomy and physiology of the brain.


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Neurology_Adams. It has been remarked that as human beings, we owe our commanding position in the animal world to two faculties: first, the ability to develop and employ verbal symbols as a background for our own ideation and as a means of transmitting thoughts, by spoken and written word, and second, the remarkable facility in the use of our hands. One curious and provocative fact is that both language and manual dexterity (as well as praxis) have evolved in relation to particular aggregates of neurons and pathways in one cerebral hemisphere (the dominant one). This is a departure from most other localized neurophysiologic activities, which are organized according to a contralateral or bilateral and symmetrical plan. The dominance of one hemisphere, usually the left, emerges in brain development together with speech and the preference for the right hand, especially its use for writing. It follows that a lack of development or loss of cerebral dominance as a result of disease deranges both these


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Neurology_Adams. with speech and the preference for the right hand, especially its use for writing. It follows that a lack of development or loss of cerebral dominance as a result of disease deranges both these traits, causing aphasia and apraxia.


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Neurology_Adams. There is abundant evidence that higher animals are able to communicate with one another by vocalization and gesture. However, the content of their communication is their feeling or reaction of the moment. This emotional language, as it is called, was studied by Charles Darwin, who noted that it undergoes increasing differentiation in the animal kingdom. Only in the chimpanzee do the first semblances of propositional language become recognizable. Indeed, there are distinct differences between the human and chimp versions of a gene called FOXP2, which has been linked to the ability to produce language, as noted in Chap. 27 (also see Balter). Another genetic influence on language has been found by Somerville and colleagues, who studied the locus implicated by a deletion in Williams syndrome and found that a duplication at this site caused a severe delay in the acquisition of expressive speech (see Chap. 37 for a discussion of the skills that are affected in Williams syndrome).


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Neurology_Adams. Instinctive patterns of emotional expression are, of course, also observed in human beings. They are the earliest modes of expression to appear (in infancy) and may have been the original forms of speech in primitive human beings. Moreover, the utterances we use to express joy, anger, and fear are retained even after destruction of all the language areas in the dominant cerebral hemisphere. The neural arrangement for this paralinguistic form of communication (intonation, exclamations, facial expressions, eye movements, body gestures), which subserves emotional expression, is bilateral and symmetrical and does not depend solely on the cerebrum. The experiments of Cannon and Bard demonstrated that emotional expression is possible in animals even after removal of both cerebral hemispheres provided that the diencephalon, particularly its hypothalamic part, remains intact. In the human infant, emotional expression is well developed at a time when much of the cerebrum is still immature.


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Neurology_Adams. Propositional, or symbolic language differs from emotional language in several ways. Instead of communicating feelings, it is the means of transferring ideas from one person to another, and it requires the substitution of a series of sounds or marks for objects, persons, and concepts. This is the essence of language. It is not instinctive but learned and is therefore subject to all the modifying social and cultural influences of the environment. However, the learning process becomes possible only after the nervous system has attained a certain degree of maturation. Mature language function involves the comprehension, formulation, and transmission of ideas and feelings by the use of conventionalized verbal symbols, sounds, and gestures and their sequential ordering according to accepted rules of grammar. Facility in symbolic language, which is acquired over a period of 15 to 20 years, depends on maturation of the nervous system and on education. Many attempts have been made to


Neurology_Adams

Neurology_Adams. rules of grammar. Facility in symbolic language, which is acquired over a period of 15 to 20 years, depends on maturation of the nervous system and on education. Many attempts have been made to crystallize the essential difference between human language and that of the higher primates that are able to communicate. Such distinctions, of course, bear on the definitions of language-dependent function, such as thinking, analysis, synthesis, and creativity. Beyond simply the complexity and range of symbolic representation and grammar available to humans in comparison to animals, Chomsky has proposed that the ability to frame recursive ideas (ones that refer to themselves by embedded phrases, such as: “John’s sister’s house”) underlies creativity in human language and an infinite variety of sentences. This has been challenged but is an interesting concept.


Neurology_Adams

Neurology_Adams. Although speech and language are closely interwoven functions, they are not synonymous. Language refers to the production and comprehension of words whereas speech refers to the articulatory and phonetic aspects of verbal expression. A derangement of language function is always a reflection of an abnormality of the brain and, more specifically of the dominant cerebral hemisphere. A disorder of speech may have a similar origin, but not necessarily; it may be a result of abnormalities in different parts of the brain or to extracerebral mechanisms.


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Neurology_Adams. The profound importance of language may not be fully appreciated unless one reflects on the proportion of our time devoted to purely verbal pursuits. External speech, or exophasia, by which is meant the expression of thought by spoken or written words and the comprehension of the spoken or written words of others, is an almost continuous activity when human beings gather together. This contrasts with inner speech, or endophasia, that is, the silent processes of thought and the formulation in our minds of unuttered words on which thought depends. The latter is almost incessant during our preoccupations, as we think always with words. Thought and language are thus inseparable. In learning to think, the child talks aloud to himself and only later learns to suppress the vocalization. Even adults may mutter subconsciously when pondering a difficult proposition. As Gardiner has remarked, any abstract thought can be held in mind only by the words or mathematic symbols denoting it. It is


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Neurology_Adams. adults may mutter subconsciously when pondering a difficult proposition. As Gardiner has remarked, any abstract thought can be held in mind only by the words or mathematic symbols denoting it. It is virtually impossible to comprehend what is meant by the word religion, for example, without the controlling and limiting consciousness of the word itself. “Words have thus become an integral part of the mechanism of our thinking and remain for ourselves and for others the guardians of our thoughts” (quoted from Brain). This is the reasoning that persuaded Head, Wilson, Goldstein, and others that any comprehensive theory of language must include explanations in terms not only of cerebral anatomy and physiology but also of the psycholinguistic processes that are involved.


Neurology_Adams

Neurology_Adams. Disorders of speech and language may be broadly characterized under four headings; 1. Loss or impairment of the production or comprehension of spoken or written language because of an acquired lesion of the brain. This is the condition called aphasia or dysphasia.


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Neurology_Adams. 2. Disturbances of speech and language with diseases that globally affect higher-order mental function, that is, confusion, delirium, mental retardation, and dementia. Speech and language functions are seldom lost in these conditions but are deranged as part of a general impairment of perceptual and intellectual functions (see Chap. 21). Common to this category are certain special disorders of speech, such as mutism as outlined by Geschwind in his article on the “non-aphasic disorders of speech” (1964) and extreme perseveration (palilalia and echolalia), in which the patient repeats, parrot-like, sounds, words, and phrases. The odd constructs of language and other disorders of verbal communication of schizophrenics and some autistic individuals, extending to the production of meaningless phrases, neologisms, or jargon, are probably best included in this category as well but they derive from a disorder of thought.


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Neurology_Adams. 3. A defect in articulation with intact mental functions, and comprehension of spoken and written language and normal syntax (grammatical construction of sentences). This is a pure motor disorder of the muscles of articulation and may be a result of flaccid or spastic paralysis, rigidity, repetitive spasms (stuttering), or ataxia. The terms dysarthria and anarthria are applied to this category of speech disorder. 4. An alteration or loss of voice because of a disorder of the larynx or its innervation—aphonia or dysphonia. Articulation and language are unaffected. Chapter 27 fully considers the important but separable category of developmental disorders of speech and language.


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Neurology_Adams. The conventional teaching, based on correlations between various disorders of language and damage to particular areas of the brain, postulates four main language areas, situated in most persons in the left cerebral hemisphere (Fig. 22-1). The entire language zone that encompasses these areas is perisylvian, that is, it borders the sylvian fissure. Two language areas are receptive and two are executive, that is, the latter are concerned with the production (output) of language. The main receptive area, subserving the perception of spoken and probably of internal language, occupies the posterosuperior temporal area (the posterior portion of area 22) and Heschl gyri (areas 41 and 42). The posterior part of area 22 in the planum temporale is referred to as Wernicke area. A second receptive area occupies the angular gyrus (area 39) in the inferior parietal lobule, anterior to the visual receptive areas. The supramarginal gyrus, which lies between these auditory and visual language


Neurology_Adams

Neurology_Adams. area occupies the angular gyrus (area 39) in the inferior parietal lobule, anterior to the visual receptive areas. The supramarginal gyrus, which lies between these auditory and visual language “centers,” and the inferior temporal region, just anterior to the visual association cortex, are probably part of the language apparatus as well. Here are located the integrative centers for cross-modal visual and auditory language functions.


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Neurology_Adams. The main executive, or output, region, situated at the posterior end of the inferior frontal convolution (Brodmann areas 44 and 45), is referred to as Broca area and is concerned with motor aspects of speech. Of note, this area is immediately adjacent to the facial motor area of the precentral gyrus. In some models of language, visually perceived words are given expression in writing through a fourth language area, the so-called Exner writing area in the posterior part of the second frontal convolution. However, this latter concept is controversial in view of the fact that widely separated parts of the language zone may cause a disproportionate disorder of writing. In any case, there are two parallel systems for understanding the spoken word and producing speech, and for the understanding of the written word and producing writing. They develop separately but are the integral components of the propositional, or semantic, system.


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Neurology_Adams. These sensory and motor language areas are intricately connected with one another by a rich network of nerve fibers, one large bundle of which, the arcuate fasciculus, passes through the isthmus of the temporal lobe and around the posterior end of the sylvian fissure; other connections may traverse the external and extreme capsules of the lenticular nuclei (subcortical white matter of the insula). Many additional corticocortical connections lead into the perisylvian zones and project from them to other parts of the brain. Of special importance for the production of speech are the short association fibers that join the Broca area with the lower rolandic cortex (precentral gyrus), which, as mentioned previously, innervates the muscles of the lips, tongue, pharynx, and larynx. The perisylvian language areas are also connected with the striatum and thalamus and with corresponding areas in the nondominant cerebral hemisphere through the corpus callosum and anterior commissure (see Fig.


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Neurology_Adams. language areas are also connected with the striatum and thalamus and with corresponding areas in the nondominant cerebral hemisphere through the corpus callosum and anterior commissure (see Fig. 23-6).


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Neurology_Adams. Having indicated the main regions involved with language, there remains considerable difference of opinion concerning the status of cortical language areas, and objection has been made to calling them “centers,” for they do not represent histologically or circumscribed structures of constant function. Moreover, a neuroanatomist would not be able to distinguish the cortical language areas microscopically from the cerebral cortex that surrounds them. Knowledge of the anatomy of language has come almost exclusively from the postmortem study of humans with focal brain diseases. Two major theories have emerged from these studies. One has subdivided the language zone into separate afferent (auditory and visual) receptive parts, connected by identifiable tracts to the executive (efferent–expressive) centers. Depending on the exact location of the lesions, a number of special syndromes are elicited.


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Neurology_Adams. The other broad theory, advanced originally by Marie (he later claims to have changed his mind) and supported by Head, Wilson, Brain, and Goldstein, favored the idea of a single language mechanism roughly localized in the opercular, or perisylvian region of the dominant cerebral hemisphere. The aphasia in any particular case was presumed to be a result of the summation of damage to input or output modalities relative to this central language zone. Undeniably, there is recognizable afferent and efferent localization within the perisylvian language area, as discussed previously, but there is also an undifferentiated central integrative mass action, in which the degree of deficit is to a considerable extent influenced by the size of the lesion. In addition, a strict division of aphasias into expressive and receptive, while still a strong practical concept, is not fully borne out by clinical observation. Nevertheless, there are several localizable language functions in the perisylvian


Neurology_Adams

Neurology_Adams. expressive and receptive, while still a strong practical concept, is not fully borne out by clinical observation. Nevertheless, there are several localizable language functions in the perisylvian cortex.


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Neurology_Adams. Carl Wernicke more than any other person must be credited with the anatomic–psychologic scheme upon which many contemporary ideas of aphasia rest. Earlier, Paul Broca (1865), and, even before him, Dax (1836), made the fundamental observations that a lesion of the insula and the overlying operculum deprived a person of speech and such lesions were always in the left hemisphere. Wernicke’s thesis was that there were two major anatomic loci for language: (1) an anterior locus, in the posterior part of the inferior frontal lobe (Broca area), in which were contained the “memory images” of speech movements, and (2) the insular region and adjoining parts of the posterior perisylvian cortex, in which were contained the images of sounds. Meynert had already shown that aphasia could occur with lesions in the temporal lobe, the Broca area being intact. Wernicke believed that the fibers between these regions ran in the insula and mediated the reflex arc between the heard and spoken word. Later,


Neurology_Adams

Neurology_Adams. in the temporal lobe, the Broca area being intact. Wernicke believed that the fibers between these regions ran in the insula and mediated the reflex arc between the heard and spoken word. Later, Wernicke came to accept von Monakow’s view that the connecting fibers ran around the posterior end of the sylvian fissure, in the arcuate fasciculus. Wernicke gave a comprehensive description of the receptive, or sensory, aphasia that now bears his name. The four main features he pointed out were (1) a disturbance of comprehension of spoken language and (2) of written language (alexia), (3) agraphia, and (4) fluent paraphasic speech. In Broca aphasia, by contrast, comprehension was intact, but the patient was mute or employed only a few simple words.


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Neurology_Adams. Wernicke also theorized that a lesion interrupting the connecting fibers between the two cortical speech areas would leave the patient’s comprehension undisturbed but would prevent the intact sound images from exerting an influence on the choice of words. Wernicke proposed that this variety of aphasia be called Leitungsaphasie, or conduction aphasia (called central aphasia by Kurt Goldstein and deep aphasia by Martin and Saffran). Careful case analyses since the time of Broca and Wernicke have borne out these associations between a receptive (Wernicke) type of aphasia and lesions in the posterior perisylvian region, and between a predominantly (Broca) motor aphasia and lesions in the posterior part of the inferior frontal lobe and the adjacent insular and opercular regions of the frontal cortex. We have certainly encountered cases that conform to the Wernicke model of conduction aphasia; the lesion in these cases may lie in the parietal operculum, involving the white matter deep to


Neurology_Adams

Neurology_Adams. cortex. We have certainly encountered cases that conform to the Wernicke model of conduction aphasia; the lesion in these cases may lie in the parietal operculum, involving the white matter deep to the supramarginal gyrus, where it presumably interrupts the arcuate fasciculus and posterior insular subcortex (the issue of conduction aphasia is discussed further on).


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Neurology_Adams. How these regions of the brain are organized into separable but interactive modules, resulting in the complex behavior of which we make daily use in interpersonal communication, is still being studied by linguists and cognitive neuropsychologists. They have dissected language into its most basic elements—phonemes (the smallest units of sound recognizable as language), morphemes (the smallest meaningful units of a word), graphemes, lexical and semantic elements (words and their meanings), and syntax (sentence structure). In general, as a restatement of the Wernicke-Broca scheme, phonologic speech output difficulties are derived from left frontal lesions; semantic–comprehension difficulties are the result of left temporal lesions; and alexia and agraphia are associated with inferior parietal lesions. These “modules” of language have been diagrammed by psycholinguists as a series of boxes and are connected to one another by arrows to indicate the flow of information and the manner in


Neurology_Adams

Neurology_Adams. lesions. These “modules” of language have been diagrammed by psycholinguists as a series of boxes and are connected to one another by arrows to indicate the flow of information and the manner in which they influence the spoken output of language. “Boxologies,” as they are called, are consistent with current cognitive theory, which views language functions as the result of synchronized activity in vast neuronal networks made up of many cerebrocortical regions and their interconnecting pathways (Damasio and Damasio, 1989).


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Neurology_Adams. On the other hand, despite this level of theoretical sophistication, attempts to delineate the anatomy of speech and language disorders by means of conventional brain imaging techniques in aphasic patients have been somewhat disappointing. In early studies using CT, LeCours and Lhermitte were unable to establish a consistent correspondence between the type of aphasia and the location of the demonstrable lesion. Similarly, Willmes and Poeck, in a retrospective study of 221 aphasic patients, failed to find an unequivocal association between the type of aphasia and the CT localization of the lesion. These poor correlations are in part related to the timing and the crudity of CT. MRI performed soon after a stroke show somewhat more consistent correlations between the type of language disturbance and the location of lesions in the perisylvian cortex, but lesions in identical locations may produce functionally different language disorders. Functional magnetic resonance imaging (fMRI), while


Neurology_Adams

Neurology_Adams. and the location of lesions in the perisylvian cortex, but lesions in identical locations may produce functionally different language disorders. Functional magnetic resonance imaging (fMRI), while subjects are engaged in language production and comprehension, provides an additional perspective for understanding the language process, but so far only the broadest rules of localization can be confirmed. Studies of blood flow and topographic physiology during the acts of reading and speaking, while generally affirming nineteenth-century models of language, have shown widespread activation of Wernicke and Broca areas, as well as of the supplementary motor area and areas of the opposite hemisphere (see Price).


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Neurology_Adams. Although localization of the lesion that produces aphasia is in most instances roughly predictable from the clinical deficit, there are wide variations. The inconsistency has several explanations, one being that the net effect of any lesion depends not only on its locus and extent but also on the degree of cerebral dominance, that is, on the degree to which the nondominant hemisphere assumes language function after damage to the dominant one. According to this view, a left-sided lesion has less effect on language function if cerebral dominance is poorly established than if dominance is strong. In all likelihood, the variability between patients in lesion location and the characteristics of aphasia has to do with subtle differences in the organization of the language cortices. Another explanation invokes the poorly understood concept that individuals differ in the ways in which they acquire language as children. This is believed to play a role in making available alternative means for


Neurology_Adams

Neurology_Adams. invokes the poorly understood concept that individuals differ in the ways in which they acquire language as children. This is believed to play a role in making available alternative means for accomplishing language tasks when the method initially learned has been impaired through brain disease. The extent to which improvement of aphasia represents “recovery” of function or generation of new modes of response has not been settled.


Neurology_Adams

Neurology_Adams. The functional supremacy of one cerebral hemisphere is fundamental to language function. There are many ways of determining that the left side of the brain is dominant: (1) by the loss of speech that occurs with disease in parts of the left hemisphere and its preservation with lesions involving corresponding parts of the right hemisphere; (2) by preference for and greater facility in the use of the right hand, foot, and eye in most persons; (3) by the arrest of speech with a focal seizure or with electrical or magnetic stimulation of the anterior (left) language area; (4) by the injection of sodium amytal or an equivalent drug into the left internal carotid artery (the Wada test—a procedure that produces mutism for a minute or two, followed by misnaming, including perseveration and substitution; misreading; and paraphasic speech); (5) by dichotic listening, in which different words or phonemes are presented simultaneously to the two ears (yielding a right ear–left hemisphere


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Neurology_Adams. substitution; misreading; and paraphasic speech); (5) by dichotic listening, in which different words or phonemes are presented simultaneously to the two ears (yielding a right ear–left hemisphere advantage); (6) by observing increases in cerebral blood flow during language processing; and (7) by lateralization of speech and language functions following commissurotomy.


Neurology_Adams

Neurology_Adams. Language hemisphere dominance is ostensibly related to hand dominance, but this is more of a supposition than a statement. Approximately 90 to 95 percent of the general population is right handed; that is, they innately choose the right hand for intricate, complex acts and are more skillful with it. The preference is more complete in some persons than in others. Most individuals are neither completely right handed nor completely left handed but strongly favor one hand for more complicated tasks. The reason for hand preference is not fully understood. There is strong evidence of a hereditary factor but the mode of inheritance is uncertain. Learning is also a factor; many left-handed children are shifted at an early age to right (shifted sinistrals) because it had been a perceived handicap to be left-handed in a right-handed world. Most right-handed persons, when obliged to use only one eye (looking through a keyhole, gun sight, telescope, etc.), sight with the right eye, and it has


Neurology_Adams

Neurology_Adams. to be left-handed in a right-handed world. Most right-handed persons, when obliged to use only one eye (looking through a keyhole, gun sight, telescope, etc.), sight with the right eye, and it has been stated that eye preference coincides with hand preference. Even if true, this still does not account for hemispheral dominance. It is, however, noteworthy that handedness develops simultaneously with language. The most that can be said at present is that localization of language and a preference for one eye, hand, and foot, as well as praxis, are all manifestations of some fundamental, partly inherited tendency for hemispheric specialization.


Neurology_Adams

Neurology_Adams. There are slight but definite anatomic differences between the dominant and the nondominant cerebral hemispheres. Yakovlev and Rakic, in a study of infant brains, observed that the corticospinal tract coming from the left cerebral hemisphere contains more fibers and decussates higher than the tract from the right hemisphere. More pertinent to language, the planum temporale, the region on the superior surface of the temporal lobe posterior to Heschl gyri and extending to the posterior end of the sylvian fissure, is slightly larger on the left in 65 percent of brains and larger on the right in only 11 percent (Geschwind and Levitsky). LeMay and Culebras noted in cerebral angiograms that the left sylvian fissure is longer and more horizontal than the right and that there is a greater mass of cerebral tissue in the area of the left temporoparietal junction. CT studies have shown the right occipital horn to be smaller than the left, indicative perhaps of a greater right-sided development


Neurology_Adams

Neurology_Adams. cerebral tissue in the area of the left temporoparietal junction. CT studies have shown the right occipital horn to be smaller than the left, indicative perhaps of a greater right-sided development of visuospatial connections. Also, subtle cytoarchitectonic asymmetries of the auditory cortex and posterior thalamus have been described; these and other biologic aspects of cerebral dominance have been reviewed by Geschwind and Galaburda particularly as they relate to developmental dyslexia (see Chap. 27).


Neurology_Adams

Neurology_Adams. Left-handedness may result from disease of the left cerebral hemisphere in early life; this probably accounts for its higher incidence among the cognitively impaired and brain injured. Presumably, the neural mechanisms for language then come to be represented during early development in the right cerebral hemisphere. Handedness and cerebral dominance may fail to develop in some individuals; this is particularly true in certain families. In these individuals, defects in reading as well as the faults of stuttering, mirror writing, and general clumsiness are frequent.


Neurology_Adams

Neurology_Adams. In right-handed individuals, aphasia is almost invariably related to a left cerebral lesion; aphasia in such individuals as a result of purely right cerebral lesions (“crossed aphasia”) is very rare, occurring in only 1 percent of cases (Joanette et al). Cerebral language dominance in ambidextrous and left-handed persons is not nearly so uniform. In a large series of left-handed patients with acquired aphasia, 60 percent had lesions confined to the left cerebral hemisphere (Goodglass and Quadfasel). Furthermore, in the relatively rare case of aphasia caused by a right cerebral lesion, the patient is nearly always left handed and the language disorder is less severe and less enduring than in right-handed patients with comparable lesions in the left hemisphere (Gloning; Subirana). Taken together, these findings suggest a bilateral—albeit unequal—representation of language functions in non-right-handed patients. This has been affirmed by the Wada test; Milner and colleagues found


Neurology_Adams

Neurology_Adams. together, these findings suggest a bilateral—albeit unequal—representation of language functions in non-right-handed patients. This has been affirmed by the Wada test; Milner and colleagues found evidence of bilateral speech representation in 32 (about 15 percent) of 212 consecutive left-handed patients.


Neurology_Adams

Neurology_Adams. The undoubted language capacities of the nondominant hemisphere have been documented by lesional neurology. In cases of congenital absence (or surgical section) of the corpus callosum, which permits the testing of each hemisphere, there has been virtually no demonstrable language function of the right hemisphere. However, Levine and Mohr found that the nondominant hemisphere retains a limited capacity to produce oral speech after extensive damage to the dominant hemisphere; their patient recovered the ability to sing, recite, curse, and utter oneor two-word phrases, all of which were completely abolished by a subsequent right hemisphere infarction. The fact that varying amounts of language function may remain after dominant hemispherectomy in adults with glioma also suggests a definite though limited capacity of the adult nondominant hemisphere for language production. Kinsbourne’s observations of the effect of sodium amytal injections into the right-hemispheral arteries of patients


Neurology_Adams

Neurology_Adams. limited capacity of the adult nondominant hemisphere for language production. Kinsbourne’s observations of the effect of sodium amytal injections into the right-hemispheral arteries of patients who are aphasic from left-sided lesions make the same point.


Neurology_Adams

Neurology_Adams. Despite its minimal contribution to the purely linguistic or propositional aspects of language, the right hemisphere does have a role in the implicit communication of emotion through the subtleties of propositional language. These modulative aspects of language are subsumed under the term prosody, by which is meant the melody of speech, its intonation, inflection, and pauses, all of which have emotional overtones. The prosodic components of speech and the gestures that accompany them enhance the meaning of the spoken word and endow speech with its richness and vitality. The related issue of an individual’s accent, which carries such a strong regional identity and is acquired early in life, may also have an anatomic basis, but one that remains obscure (see later comments on the “Foreign Accent Syndrome”).


Neurology_Adams

Neurology_Adams. Many diseases and focal cerebral lesions mute or reduce the prosody of speech, the most dramatic examples being the hypophonic monotone of Parkinson disease and the effortful utterances of Broca’s aphasia. Largely through the work of Ross, it has become apparent that prosody is also greatly disordered in patients with strokes involving portions of the nondominant hemisphere that mirror the language areas of the left hemisphere. In these cases, there is impairment both of comprehension and of production of the emotional content of speech and its accompanying gestures. A prospective study of middle cerebral artery infarctions by Darby corroborated this view: aprosodia, as it has come to be called, was present only in those patients with lesions in the territory of the inferior division of the right middle cerebral artery. The deficit was most prominent soon after the stroke and was not found with lacunar lesions. In our patients, using bedside tests, we have had difficulty in


Neurology_Adams

Neurology_Adams. of the right middle cerebral artery. The deficit was most prominent soon after the stroke and was not found with lacunar lesions. In our patients, using bedside tests, we have had difficulty in appreciating aprosodia as a result solely of right perisylvian lesions, and in most cases, the damage has been more widespread.


Neurology_Adams

Neurology_Adams. There has been recent interest in a role for the cerebellum in language function, based partly on observations in the Williams syndrome, in which cognitive impairment is associated with a preservation of language skills that is sometimes striking in degree (see Chap. 38). In this disease, the cerebellum is spared in the face of greatly diminished volume of the cerebral hemispheres (see Leiner et al). Some studies of cerebral blood flow also implicate the cerebellum in various language functions; based on our clinical experience, however, we would judge any language deficits from cerebellar disease to be subtle or nonexistent. Dysarthria, of course, is common with cerebellar disease.


Neurology_Adams

Neurology_Adams. In the investigation of aphasia, it is first necessary to inquire into the patient’s native language, handedness, and previous level of literacy and education. It has been surmised that following the onset of aphasia, individuals who had been fluent in more than one language (polyglots) improved more quickly in their native language than in a subsequently acquired one (a derivative of the Ribot law of retained distant memory). This rule seems to hold if the patient is not truly fluent in the more recently acquired language or has not used it for a long time. More often, the language most used before the onset of the aphasia will recover first (Pitres law). Usually, if adequate testing is possible, more or less the same aphasic abnormalities are found in both the first and the more recently acquired language. Dementing illnesses such as Alzheimer disease, however, do cause increasing use of the first acquired language.


Neurology_Adams

Neurology_Adams. Many naturally left-handed children are trained to use the right hand for writing; therefore, in determining handedness, one must ask which hand is preferred for throwing a ball, threading a needle, sewing, or using a tennis racket or hammer, and which eye is used for sighting a target with a rifle or other instrument. It is important, before beginning the examination, to determine whether the patient is alert and can participate reliably in testing, as accurate assessment of language depends on these factors.


Neurology_Adams

Neurology_Adams. One should quickly ascertain whether the patient has other gross signs of a cerebral lesion such as hemiplegia, facial weakness, homonymous hemianopia, or cortical sensory loss. When a constellation of these major neurologic signs is present, the aphasic disorder is usually of the total (global) type. A right brachiofacial paralysis aligns with Broca’s aphasia; in contrast, a restricted right hemianopia or quadrantanopia is a common accompaniment of Wernicke aphasia, and hemiparesis is absent. Dyspraxia of limbs and speech musculature in response to spoken commands or to visual mimicry is generally associated with Broca aphasia, but sometimes with Wernicke aphasia. Homonymous hemianopia without motor weakness tends often to be linked to pure word blindness, to alexia with or without agraphia, and to anomic aphasia.


Neurology_Adams

Neurology_Adams. The bedside analysis of aphasic disorders that we find most useful entails the systematic testing of six aspects of language function: conversational speech, comprehension, repetition, reading, writing, and naming. Simply engaging the patient in conversation permits assessment of the motor aspects of speech (praxis and prosody), fluency, and language formulation. If the disability consists mainly of sparse, laborious, nonfluent speech, it suggests, of course, Broca aphasia, and this possibility can be pursued further by tests of repeating from dictation and by special tests of praxis of the oropharyngeal muscles. Fluent but empty paraphasic speech with impaired comprehension is indicative of Wernicke aphasia. Impaired comprehension but perfectly normal formulated speech and intact ability to read suggest the rare syndrome of pure word deafness.


Neurology_Adams

Neurology_Adams. When conversation discloses virtually no abnormalities, other tests may still be revealing. The most important of these are reading, writing, repetition, and naming. Reading aloud single letters, words, and text may disclose the dissociative syndrome of pure word blindness. Except for this syndrome and isolated mutism (aphemia; see earlier), writing is disturbed in all forms of aphasia. Literal and verbal paraphasic errors may appear in milder cases of Wernicke aphasia as the patient reads aloud from a text or from words in the examiner’s handwriting. Similar errors appear even more frequently when the patient is asked to explain the text, read aloud, or give an explanation in writing.


Neurology_Adams

Neurology_Adams. Testing the patient’s ability to repeat spoken language is a simple and important maneuver in the evaluation of aphasic disorders. As with other tests of aphasia, it may be necessary to increase the complexity of the test from digits and simple words to complex words, phrases, and sentences to disclose the full disability. Defective repetition occurs in all the major forms of aphasia (Broca, Wernicke, and global) because of lesions in the perisylvian language areas. The patient may be unable to repeat what is said to him, despite relatively adequate comprehension—the hallmark of conduction aphasia. Contrariwise, normal repetition in an aphasic patient (transcortical aphasia) indicates that the perisylvian area is largely intact. In fact, the tendency to repeat may be excessive (echolalia). Preserved repetition is also characteristic of anomic aphasia and occurs occasionally with subcortical lesions. Disorders confined to naming, other language functions (reading, writing, spelling)


Neurology_Adams

Neurology_Adams. Preserved repetition is also characteristic of anomic aphasia and occurs occasionally with subcortical lesions. Disorders confined to naming, other language functions (reading, writing, spelling) being adequate, are diagnostic of amnesic, or anomic, aphasia and referable usually to lower temporal lobe lesions.


Neurology_Adams

Neurology_Adams. These deficits can be quantified by the use of any one of several examination procedures. Those of Goodglass and Kaplan (Boston Diagnostic Aphasia Examination [BDAE]) and of Kertesz (Western Aphasia Battery [WAB]) are the most widely used in the United States. The use of these procedures will enable one to predict the type and localization of the lesion in approximately two-thirds of the patients, which is not much better than detailed bedside examination. Using these tests, aphasia of the Broca, Wernicke, conduction, global, and anomic types accounted for 392 of 444 unselected cases studied by Benson.


Neurology_Adams

Neurology_Adams. In analyzing disorders of speech and language in the clinic or at the bedside, the first objective is to separate dysarthria, or slurred speech with preservation of language, from a genuine impairment in language function, aphasia. Here, we offer a practical approach to aphasia. Dysarthria is addressed in a later section. To recapitulate, the features of a language disorder that are used to advantage by the examiner in determining the type of aphasia are • Natural sounding fluency, including normal cadence, the use of prepositions, and correct grammar • Comprehension of language • The proper selection, use, and relationships between words • Naming of displayed objects • The ability to repeat in comparison to spontaneous speech


Neurology_Adams

Neurology_Adams. This type of systematic examination will enable one to decide whether a patient has a predominantly: (1) motor or Broca aphasia, sometimes called “expressive,” “anterior,” or “nonfluent” aphasia; (2) sensory or Wernicke aphasia, referred to also as “receptive,” “posterior,” or “fluent” aphasia; (3) a total or global aphasia, with loss of all or nearly all speech and language functions; (4) transcortical aphasia, meaning a motor or sensory aphasia with preserved repetition; or (5) one of the disconnection language syndromes, such as conduction aphasia, word deafness (auditory verbal agnosia), and word blindness (visual verbal agnosia or alexia). In addition, there is a condition of mutism, or a complete absence of verbal output, but this syndrome does not permit one to predict the exact locus of the lesion. Anomia (also called nominal or amnesic aphasia, meaning loss of naming ability) and the impaired ability to communicate by writing (agraphia) are found to some degree in practically


Neurology_Adams

Neurology_Adams. of the lesion. Anomia (also called nominal or amnesic aphasia, meaning loss of naming ability) and the impaired ability to communicate by writing (agraphia) are found to some degree in practically all types of aphasia. As for agraphia, it rarely exists alone. Table 22-1 summarizes these main aphasic syndromes, which are described in the following text. Even though these descriptions are based largely on deficits from vascular occlusion, they serve well in most circumstances of focal brain disease that cause language disturbances.


Neurology_Adams

Neurology_Adams. Broca aphasia conforms to a primary deficit in language output and speech production with relative preservation of comprehension. There is a wide range of variation in the severity of the motor speech deficit, from the mildest poverty of speech and minimal dysarthria with entirely intact comprehension and ability to write (so-called Broca area aphasia; “mini-Broca”), to a complete loss of all means of lingual, phonetic, written, and gestural communication. Because the muscles that can no longer be used in speaking may still function in other acts, they are not paralyzed. The term apraxia has been imprecisely applied to this deficit in oro-buccal-lingual use (it does not represent the loss of a previously learned ability) but there are accompanying apractic deficits of the orofacial apparatus as noted in the following text.


Neurology_Adams

Neurology_Adams. In the most advanced form of the syndrome, patients lose all power of speaking. Not a word can be uttered in conversation, in attempting to read aloud, or in trying to repeat words that are heard. One might suspect that in this mutism the lingual and phonatory apparatus is paralyzed, until patients are observed to have no difficulty chewing, swallowing, clearing the throat, crying or shouting, and even vocalizing without words. Occasionally, the words yes and no can be uttered, usually in the correct context. Or patients may repeat a few stereotyped utterances over and over again, as if compelled to do so, a disorder referred to as monophasia (Critchley), recurring utterance (Hughlings Jackson), verbal stereotypy, or verbal automatism. If speech is possible at all, certain habitual expressions, such as “hi,” “fine, thank you,” or “good morning,” seem to be the easiest to elicit, and the words of well-known songs may be sung hesitantly, or counting by consecutive numbers may remain


Neurology_Adams

Neurology_Adams. such as “hi,” “fine, thank you,” or “good morning,” seem to be the easiest to elicit, and the words of well-known songs may be sung hesitantly, or counting by consecutive numbers may remain facile. When angered or excited, an expletive may be uttered, thus emphasizing the fundamental distinction between propositional and emotional speech. The patient recognizes his verbal ineptitude and mistakes. Repeated failures in speech cause demonstrations of exasperation.


Neurology_Adams

Neurology_Adams. As a result of damage to the adjacent prerolandic motor area, the arm and lower part of the face are usually weak on the right side. The tongue may early on deviate away from the lesion, that is, to the right, and be slow and awkward in rapid movements. For a time, despite the relative preservation of auditory comprehension and the ability to read, commands to purse, smack, or lick the lips, or to blow and whistle and make other purposeful orolingual and facial movements are poorly executed, which signifies that an apraxia has extended to certain acts involving the lips, tongue, and pharynx. In these circumstances, imitation of the examiner’s actions is performed better than spontaneous execution of acts on command. Self-initiated actions and spontaneous emotional expressions of the face, by contrast, may be normal or better preserved. From imaging findings in patients with this type of speech, it is apparent that the coordination of orolingual movements that are responsible for


Neurology_Adams

Neurology_Adams. face, by contrast, may be normal or better preserved. From imaging findings in patients with this type of speech, it is apparent that the coordination of orolingual movements that are responsible for articulation takes place in the left anterior insular cortex (see Dronkers) rather than primarily in the Broca area. Positron emission tomography (PET) shows activation of the insular region as well as of the lateral premotor cortex and the anterior pallidum during repetition of single words (Wise et al).


Neurology_Adams

Neurology_Adams. In the milder forms of Broca aphasia and in the recovery phase of the severe form, patients are able to speak aloud to some degree, but the normal cadence and parsing of speech is choppy or lacking. Words are uttered slowly and laboriously, and enunciated poorly. Missing is the normal inflection, intonation, phrasing of words in a series, and pacing of word utterances. The overall impression is one of a lack of fluency, a term that has come to be almost synonymous with aphasias that derive from damage in and around the Broca area (nonfluent aphasia). This labored, uninflected speech stands in contrast to the fluent speech of Wernicke aphasia described later, but there are exceptions in which nonfluency extends to Wernicke aphasia.


Neurology_Adams

Neurology_Adams. Language is clearly affected in a restricted way in Broca aphasia. Speech is sparse (10 to 15 words per minute as compared with the normal 100 to 115 words per minute) and consists mainly of nouns, transitive verbs, or important adjectives; phrase length is abbreviated and many of the small words (articles, prepositions, conjunctions) are omitted, giving the speech an abbreviated, telegraphic character (so-called agrammatism). The substantive content of the patient’s language permits the crude communication of ideas, sometimes despite gross expressive difficulties. Repetition of the examiner’s spoken language is as abnormal as the patient’s own speech. If a patient with nonfluent Broca aphasia has no difficulty in repetition, the condition is termed transcortical motor aphasia (see further on). Furthermore, a true defect in language production is evidenced by impairment in the content of written words and sentences. Should the right hand be paralyzed, the patient cannot print with the


Neurology_Adams

Neurology_Adams. on). Furthermore, a true defect in language production is evidenced by impairment in the content of written words and sentences. Should the right hand be paralyzed, the patient cannot print with the left one, and if the right hand is spared, the patient fails as miserably in writing to dictation or replying to questions in written form. Letters are malformed and words misspelled. Although writing to dictation is impossible, letters and words can still be copied. The dysgraphia usually corresponds in degree to the severity of the spoken disturbance, but there are exceptions in which one is far more affected.


Neurology_Adams

Neurology_Adams. The comprehension of spoken and written language, though seemingly normal under casual conditions, is usually slightly defective in the full syndrome of Broca’s aphasia and will break down under stringent testing, especially when novel or complicated material is introduced. The naming of objects and particularly parts of objects may be faulty in articulation, but the proper name can be chosen from a list. These are the most variable and controversial aspects of Broca’s aphasia, as in some patients with a loss of motor speech and agraphia as a result of cerebral infarction, the understanding of spoken and written language may be normal. Mohr and colleagues (1978) have pointed out that in such patients an initial mutism is usually replaced by a rapidly improving dyspraxic and effortful articulation (a “mini-Broca’s aphasia,” in his terms), leading to complete recovery. The lesion in such cases is restricted to a zone in and immediately around the posterior part of the inferior frontal


Neurology_Adams

Neurology_Adams. (a “mini-Broca’s aphasia,” in his terms), leading to complete recovery. The lesion in such cases is restricted to a zone in and immediately around the posterior part of the inferior frontal convolution (the latter being the Broca area per se). Mohr and colleagues (1978) have stressed the distinction between this relatively mild and restricted type of motor speech disorder and the more complex syndrome that is traditionally referred to as Broca aphasia.


Neurology_Adams

Neurology_Adams. The lesion in the major form of Broca aphasia subsumes a much larger area than the inferior frontal gyrus and includes the subjacent white matter and even the head of the caudate nucleus and putamen (Fig. 22-2), the anterior insula, and frontoparietal operculum (the term operculum refers to the cortex that borders the sylvian fissure and covers or forms a lid over the insula, or island of Reil.) In other words, the lesion in the usual form of Broca aphasia extends well beyond the so-called Broca area (Brodmann areas 44 and 45). Furthermore, persistence of Broca’s aphasia is associated with the larger type of lesion illustrated in Fig. 22-2.


Neurology_Adams

Neurology_Adams. It is interesting historically that in one of Broca’s original patients, whose expressive language had been limited to a few verbal stereotypes for 10 years before his death, inspection of the surface of the brain (the brain was never cut, although scans have since been done) disclosed an extensive lesion encompassing the left insula; the frontal, central, parietal operculum and included even part of the inferior parietal lobe posterior to the sylvian fissure. The Wernicke area was spared, refuting a prediction made at the time by Marie. Inexplicably, Broca attributed the aphasic disorder to the lesion of the frontal operculum alone, and ignored the rest of the lesion, which he considered to be a later spreading effect of the stroke. Perhaps he was influenced by the prevailing opinion of the time (1861) that articulation was a function of the inferior parts of the frontal lobes. The fact that Broca’s name later became attached to a discrete part of the inferior frontal cortex helped


Neurology_Adams

Neurology_Adams. the time (1861) that articulation was a function of the inferior parts of the frontal lobes. The fact that Broca’s name later became attached to a discrete part of the inferior frontal cortex helped to entrench the idea that Broca aphasia is equated with a lesion in the Broca area. However, as pointed out earlier, a lesion confined only to this area gives rise to a relatively modest and transient motor speech disorder (Mohr et al) or to no disorder of speech at all (Goldstein).


Neurology_Adams

Neurology_Adams. Motor speech disorders, both severe Broca aphasia and the more restricted and transient types, are most often a result of vascular lesions. Embolic stroke in the territory of the upper (rolandic, superior) division of the middle cerebral artery is the most frequent type and results in an abrupt onset of aphasia. Small strokes may give way to rapid improvement (hours to days); contrariwise, infarctions that extend beyond the central Broca region at times produce a more severe clinical syndrome than might be anticipated from the size of the lesion. It is these latter strokes, especially if the underlying frontal white matter is damaged, that tend to cause lasting speech difficulty. Because of the territory that is supplied by the superior branch of the middle cerebral artery, strokes that cause Broca aphasia are usually associated with right-sided brachiofacial paresis (face, proximal arm, and hand) as described earlier, and sometimes with a left-sided manual-brachial apraxia


Neurology_Adams

Neurology_Adams. that cause Broca aphasia are usually associated with right-sided brachiofacial paresis (face, proximal arm, and hand) as described earlier, and sometimes with a left-sided manual-brachial apraxia (sympathetic apraxia as described in Chap. 3). Atherosclerotic thrombosis, primary or metastatic tumor, subcortical hypertensive, traumatic, or anticoagulant-induced hemorrhage, and seizure, should they involve the appropriate parts of the motor language cortex, may also declare themselves by a Broca aphasia.


Neurology_Adams

Neurology_Adams. A closely related syndrome, pure word mutism (aphemia), causes the patient to be wordless (mute) but leaves inner speech intact and writing undisturbed. Anatomically, this is believed to be in the nature of a disconnection of the motor cortex (Broca area) for speech from lower centers and is described with the dissociative speech syndromes discussed further on in this chapter.


Neurology_Adams

Neurology_Adams. This syndrome comprises two main elements: (1) impairment in the comprehension of speech—basically an inability to perceive word elements, both spoken and written, and (2) a relatively fluent but paraphasic speech (further defined in the following text). The first of these grossly affects the internal stream of conversation and its attendant manipulation of symbolic language and causes a restricted form of confusion. The defect in language is manifest further by a variable inability to repeat spoken and written words. The location of the lesion in cases of Wernicke aphasia is the left superior lateral temporal lobe near the primary auditory cortex. The involvement of visual association areas or their separation from the primary visual cortices is a common accompaniment that is reflected in an inability to read (alexia).


Neurology_Adams

Neurology_Adams. In contrast to Broca aphasia, the patient with Wernicke aphasia usually talks volubly, gestures freely, and appears strangely unaware of his deficit. Speech is produced mostly without effort; the phrases and sentences appear to be of normal length and are properly intoned and articulated. These attributes, in the context of aphasic disturbances, are referred to as “fluency” of speech (i.e., Wernicke aphasia is a fluent aphasia). Despite the fluency and normal prosody, the patient’s speech is remarkably devoid of meaning. The patient with Wernicke aphasia produces many nonsubstantive words, and the words themselves are often malformed or inappropriate, a disorder referred to as paraphasia. A phoneme (the minimal unit of sound recognizable as language) or a syllable may be substituted within a word (e.g., “The grass is greel”); this is called literal paraphasia. The substitution of one word for another (“The grass is blue”) is termed verbal paraphasia or semantic substitution and is


Neurology_Adams

Neurology_Adams. a word (e.g., “The grass is greel”); this is called literal paraphasia. The substitution of one word for another (“The grass is blue”) is termed verbal paraphasia or semantic substitution and is even more characteristic of Wernicke’s aphasia. Neologisms, that is, syllables or words that are not part of the language, may also appear (“The grass is grumps”). In its extreme, the fluent, paraphasic speech of Wernicke’s aphasia may be entirely incomprehensible (gibberish or jargon aphasia). Fluency, however, is not an invariable feature of Wernicke’s aphasia. In some patients speech may be hesitant, in which case the block tends to occur in the part of the phrase that contains the central communicative (predicative) item, such as a key noun, verb, or descriptive phrase. The patient with such a disorder conveys the impression of constantly searching for the correct word and of having difficulty in finding it. Wernicke aphasia may also at times begin with complete mutism.


Neurology_Adams

Neurology_Adams. Although the motor apparatus required for the expression of language is intact, patients with severe Wernicke’s aphasia have difficulty functioning socially because they are deprived of the main means of communication. They cannot understand fully what is said to them; a few simple commands may still be executed, but there is failure to carry out complex ones. They cannot read aloud or silently with comprehension, tell others what they want or think, or write spontaneously. Written letters are often combined into meaningless words, but there may be a scattering of correct words. In trying to designate an object that is seen or felt, they cannot find the name, even though they can sometimes repeat it from dictation; nor can they write from dictation the very words that they can copy. Copying performance is notably slow and laborious and conforms to the contours of the model, including the examiner’s handwriting style. All these defects are present in varying degrees of severity and the


Neurology_Adams

Neurology_Adams. performance is notably slow and laborious and conforms to the contours of the model, including the examiner’s handwriting style. All these defects are present in varying degrees of severity and the mildest form consists of mild verbal and literal paraphasias and minimal difficulty with comprehension of grammatically complex material (“mini-Wernicke”). In general, the disturbances in reading, writing, naming, and repetition parallel the severity of impairment in comprehension. There are, however, exceptions in which either reading or the understanding of spoken language is disproportionately affected. Some aphasiologists thus speak of two Wernicke syndromes.


Neurology_Adams

Neurology_Adams. In terms of the idealized Broca-Wernicke schema, in Wernicke aphasia the motor language areas are no longer under control of the auditory and visual areas. The disconnection of the motor speech areas from the auditory and visual ones accounts for the impairment of repetition and the inability to read aloud. Reading may remain fluent, but with the same paraphasic errors that mar conversational language. The occurrence of dyslexia (impaired visual perception of letters and words) with lesions of the Wernicke area is ostensibly explained by the fact that most individuals learn to read by transforming the printed word into the auditory form before it can gain access to the integrative centers in the posterior perisylvian region. Only in the congenitally deaf is there thought to be a direct pathway between the visual and central integrative language centers.


Neurology_Adams

Neurology_Adams. Wernicke aphasia that is caused by stroke usually improves in time, sometimes to the point where the deficits can be detected only by asking the patient to repeat unfamiliar words, to name unusual objects or parts of objects, to spell difficult words, or to write complex self-generated sentences. A more favorable prognosis attends those forms in which some of the elements, for example, reading, are only slightly impaired from the outset.


Neurology_Adams

Neurology_Adams. As discussed earlier, the term Wernicke area has been applied to the posterior part of area 22 in the most lateral part of the planum temporale. As a rule, in Wernicke aphasia the lesion lies in the posterior perisylvian region (comprising posterosuperior temporal, supramarginal, angular, and posterior insular gyri) and is usually a result of embolic occlusion of the inferior (lower) division of the left middle cerebral artery. A hemorrhage confined to the subcortex of the temporoparietal region or involvement of this area by tumor, abscess, herpes encephalitis, or extension of a small putaminal or thalamic hemorrhage may have similar effects but a better prognosis. Any lesion that involves structures deep to the posterior temporal cortex, including stroke, will cause an associated right homonymous quadrantor hemianopia. Usually, there is no weakness of limbs or face for which reason the fluently aphasic patient may be misdiagnosed as psychotic or confused, especially if there is


Neurology_Adams

Neurology_Adams. homonymous quadrantor hemianopia. Usually, there is no weakness of limbs or face for which reason the fluently aphasic patient may be misdiagnosed as psychotic or confused, especially if there is jargon aphasia. According to Kertesz and Benson, persistence of Wernicke aphasia is related to a lesion that involves both the left supramarginal and angular gyri and therefore, elements of Gerstmann syndrome may be evident.


Neurology_Adams

Neurology_Adams. The posterior perisylvian region, therefore, appears to encompass a variety of language functions, and seemingly minor changes in the size and locale of the lesion are associated with important variations in the elements of Wernicke aphasia or lead to conduction aphasia, pure word blindness, or to pure word deafness (see the following text). The interesting theoretical problem is whether all the deficits observed are indicative of a unitary language function that resides in the posterior perisylvian region or, instead, of a series of separate sensorimotor activities whose anatomic pathways happen to be crowded together in a small region of the brain. In view of the multiple ways in which language is learned and deteriorates in disease, the latter hypothesis seems more likely.


Neurology_Adams

Neurology_Adams. This syndrome is caused by destruction of a large part of the language zone, embracing both Broca and Wernicke areas and much of the territory between them. The cause is usually an occlusion of the proximal left middle cerebral artery, but it may be the result of hemorrhage, tumor, abscess or other lesions, and transiently as a postictal effect. Almost invariably, in cases of global aphasia, there is a degree of right hemiplegia, hemianesthesia, and homonymous hemianopia.


Neurology_Adams

Neurology_Adams. All aspects of speech and language are affected. At most, the patient can say only a few words, usually some cliché or habitual phrase, and can imitate single sounds, or only emit a syllable, such as “ah,” or cry, shout, or moan. Many are initially mute. They may understand a few words and phrases, but, because of rapid fatigue and verbal and motor perseveration—they characteristically fail to carry out a series of simple commands or to name a series of objects. They cannot read or write or repeat what is said to them. The patient may participate in common gestures of greeting, show modesty and avoidance reactions, and engage in self-help activities. With the passage of time, some degree of comprehension of language may return, and the clinical picture that is then most likely to emerge is closest to that of a severe Broca aphasia.


Neurology_Adams

Neurology_Adams. Improvement frequently occurs when the underlying cause is cerebral trauma, compression from edema, ictal or postictal paralysis, or a transient metabolic derangement such as hypoglycemia or hyponatremia, which may also worsen the aphasia of an old lesion that had involved language areas. These terms refer to disorders of language that result not from lesions of the cortical language areas themselves but from an apparent interruption of association pathways joining the primary receptive (sensory, auditory, and visual) areas to the language areas. Included also in this category are aphasias from lesions that separate the more strictly receptive parts of the language mechanism itself from the purely motor ones (conduction aphasia; see the following text) and to lesions that isolate the perisylvian language areas, separating them from the other parts of the cerebral cortex (transcortical aphasias).


Neurology_Adams

Neurology_Adams. The anatomic basis for most of these so-called disconnection syndromes is only partly defined. The theoretical concept is an interesting one and emphasizes the importance of afferent, intercortical, and efferent connections of the language mechanisms. However, the locale of the lesion that causes loss of a language function does not localize the language function itself, a warning enunciated long ago by Hughlings Jackson. Nevertheless, the language disorders described below occur with sufficient regularity and clinical uniformity to be almost as useful as the more common types of aphasia in localization and in revealing the complexity of language functions.


Neurology_Adams

Neurology_Adams. As indicated earlier, Wernicke theorized that certain clinical symptoms would follow a lesion that effectively separated the auditory and motor language areas without directly damaging either of them. Since then a number of well-studied cases have been described that conform to his proposed model of Leitungsaphasie (conduction aphasia), which is the name he gave it. The characteristic feature is severely impaired repetition of spoken language; the defect applies to both single words and nonwords. The second essential feature is reduced but still relatively preserved comprehension in comparison to Wernicke aphasia. In other respects, the features of conduction aphasia resemble those of a mild Wernicke aphasia. They share fluency and paraphasias in self-initiated speech, in repeating what is heard, and in reading aloud; writing is also similarly impaired. Dysarthria and dysprosody are usually lacking. Speech output is normal or somewhat reduced. As mentioned, comprehension is by no


Neurology_Adams

Neurology_Adams. is heard, and in reading aloud; writing is also similarly impaired. Dysarthria and dysprosody are usually lacking. Speech output is normal or somewhat reduced. As mentioned, comprehension is by no means perfect, but compared with one who has Wernicke aphasia, the patient with conduction aphasia has relatively little difficulty in understanding words that are heard or seen and is aware of his deficit.


Neurology_Adams

Neurology_Adams. The lesion in the few autopsied cases has been located in the cortex and subcortical white matter in the upper bank of the left sylvian fissure, usually involving the supramarginal gyrus and occasionally the most posterior part of the superior temporal region. The reason for classifying this aphasia as a disconnection syndrome according to Damasio and Geschwind is that the Wernicke and Broca areas are spared, and the critical structure involved is the connection between them—the arcuate fasciculus. This fiber tract streams out of the temporal lobe, proceeding somewhat posteriorly, around the posterior end of the sylvian fissure; there it joins the superior longitudinal fasciculus, deep in the anteroinferior parietal region, and proceeds forward, deep to the suprasylvian operculum, to the motor association cortex, including the Broca and Exner areas (see Fig. 23-1). However, in most of the reported cases, including those described by the Damasios, the left auditory complex, insula, and


Neurology_Adams

Neurology_Adams. association cortex, including the Broca and Exner areas (see Fig. 23-1). However, in most of the reported cases, including those described by the Damasios, the left auditory complex, insula, and supramarginal gyrus were also involved. In any case, the usual cause of conduction aphasia is an embolic occlusion of the ascending parietal or posterior temporal branch of the middle cerebral artery, but other forms of vascular disease, particularly small subcortical hemorrhage, neoplasm, or trauma in this region produce the same syndrome.


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Neurology_Adams. Transcortical Aphasias (Preservation of Repetition) The identifying feature of these language disturbances is a preservation of the ability to repeat. Destruction of the vascular border zones between anterior, middle, and posterior cerebral arteries, usually as a result of prolonged hypotension, carbon monoxide poisoning, or other forms of anoxic–ischemic injury, may effectively isolate the intact motor and sensory language areas, all or in part, from the rest of the cortex of the same hemisphere. In the case reported by Assal and colleagues, for example, multiple infarcts had isolated all of the language area.


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Neurology_Adams. In transcortical sensory aphasia the patient suffers a deficit of auditory and visual word comprehension, making writing and reading impossible, in every way conforming to Wernicke aphasia. Speech remains fluent, with marked paraphasia, anomia, and empty circumlocutions. However, unlike the deficit in Wernicke and conduction aphasias, the ability to repeat the spoken word is preserved. This facility in repetition may be of extreme degree, taking the form of echoing, parrot-like, word, phrases, and songs that are heard (echolalia). In a series of 15 such patients, CT and isotope scans have uniformly disclosed a lesion in the posterior parietooccipital region, according to Kertesz and colleagues. In general, this disorder has a good prognosis.


Neurology_Adams

Neurology_Adams. Presumably, in transcortical sensory aphasia, as in Wernicke aphasia, information cannot be transferred to the Wernicke area for conversion into word meaning. Paraphasia is thought to result from the reduced control of the motor language areas by the auditory and visual areas, though the direct connection between them, presumably the arcuate fasciculus, is preserved. Preservation of this direct connection is said to account for the ability to repeat.


Neurology_Adams

Neurology_Adams. In transcortical motor aphasia, the patient is unable to initiate conversational speech, producing only a few grunts or syllables as in Broca-type aphasia. Comprehension is relatively preserved, but repetition is strikingly intact, distinguishing this syndrome from pure word mutism. Transcortical motor aphasia occurs in two clinical contexts: (1) in a mild or partially recovered Broca aphasia in which repetition remains superior to conversational speech (repeating and reading aloud are generally easier than self-generated speech) and (2) in states of abulia and akinetic mutism with frontal lobe damage. Several cases under our observation have resulted from infarctions in the watershed zone between the anterior and middle cerebral arteries after cardiac arrest or shock.


Neurology_Adams

Neurology_Adams. This uncommon disorder, a derivative of Wernicke aphasia originally described by Lichtheim in 1885, is characterized by an impairment of auditory comprehension and repetition and an inability to write to dictation. Self-initiated utterances are usually correctly phrased but sometimes paraphasic; spontaneous writing and the ability to comprehend written language are preserved, thus distinguishing this disorder from Wernicke aphasia. Patients with pure word deafness may declare that they cannot hear, but shouting does not help, sometimes to their surprise. Audiometric testing and auditory evoked potentials disclose no hearing defect, and nonverbal sounds, such as a doorbell, can be heard without difficulty. The patient is forced to depend heavily on visual cues and frequently uses them well enough to understand most of what is said. However, tests that prevent the use of visual cues readily uncover the deficit. If able to describe the auditory experience, the patient says that words


Neurology_Adams

Neurology_Adams. enough to understand most of what is said. However, tests that prevent the use of visual cues readily uncover the deficit. If able to describe the auditory experience, the patient says that words sound like a jumble of noises. As in the case of visual verbal agnosia (see the following text), the syndrome of pure auditory verbal agnosia is not pure, particularly at its onset, and paraphasic and other elements of Wernicke aphasia may be detected (Buchman et al). At times, this syndrome is the result of resolution of a more typical Wernicke aphasia, and it will be recognized that word deafness is an integral feature of all instances of Wernicke aphasia. Conceptually, it has been thought of as an exclusive injury of the auditory processing system therefore allowing relative preservation of internal language.


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Neurology_Adams. In most recorded autopsy studies, the lesions have been bilateral, in the middle third of the superior temporal gyri, in a position to interrupt the connections between the primary auditory cortex in the transverse gyri of Heschl and the associated areas of the superoposterior cortex of the temporal lobe. In a few cases, unilateral lesions have been localized in this part of the dominant temporal lobe (see Chap. 21). Requirements of small size and superficiality of the lesion in the cortex and subcortical white matter are best fulfilled by an embolic occlusion of a small branch of the lower division of the middle cerebral artery. Pure Word Blindness (Alexia Without Agraphia, Visual Verbal Agnosia)


Neurology_Adams

Neurology_Adams. The most striking feature of this syndrome is the retained capacity to write fluently, after which the patient cannot read what has been written (alexia without agraphia). In fact, reading of any material is greatly impaired. When the patient with alexia also has difficulty in auditory comprehension and in repeating spoken words, the syndrome corresponds more closely to Wernicke aphasia. In such cases, the individual loses the ability to understand written script, and, often, to name colors, that is, to match a seen color to its spoken name, visual verbal color anomia. Such a person can no longer name or point on command to words, although he is sometimes able to read letters or numbers. However, understanding spoken language, repetition of what is heard, writing spontaneously and to dictation, and conversation are all intact. The ability to copy words is impaired but is better preserved than reading, and the patient may even be able to spell a word or to identify a word by having it


Neurology_Adams

Neurology_Adams. and conversation are all intact. The ability to copy words is impaired but is better preserved than reading, and the patient may even be able to spell a word or to identify a word by having it spelled to him or by reading one letter at a time (letter-by-letter reading). In some cases, the patient manages to read single letters but not to join them together (asyllabia).


Neurology_Adams

Neurology_Adams. Autopsies of such cases have usually demonstrated a lesion that destroys the left visual cortex and underlying white matter, particularly the geniculocalcarine tract, as well as the callosal connections of the right visual cortex with the intact language areas of the dominant hemisphere (see “Disconnection Syndromes” in Chap. 23). In the case originally described by Dejerine in 1892, the disconnection occurred in the posterior part (splenium) of the corpus callosum, wherein lie the connections between the visual association areas of the two hemispheres (see


Neurology_Adams

Neurology_Adams. Fig. 23-6). More often, the callosal pathways are interrupted in the forceps major or in the periventricular region (Damasio and Damasio, 1983). In either event, the patient is blind in the right half of each visual field by virtue of the left occipital lesion, and visual information reaches only the right occipital lobe; however, this information cannot be transferred, via the callosal pathways to the language area of the left hemisphere. A rare variant of this syndrome takes the form of alexia without agraphia and without hemianopia. A lesion deep in the white matter of the left occipital lobe, at its junction with the parietal lobe, interrupts the projections from the intact (right) visual cortex to the language areas, but spares the geniculocalcarine pathway (Greenblatt). This lesion, coupled with one in the splenium, prevents all visual information from reaching the language areas, including the angular gyrus, and Wernicke area.


Neurology_Adams

Neurology_Adams. In yet other cases, the lesion is confined to the angular gyrus or the subjacent white matter. In such cases also, a right homonymous hemianopia will be absent, but the alexia may be combined with agraphia and other elements of the Gerstmann syndrome, that is, right-left confusion, acalculia, and finger agnosia (see “Gerstmann Syndrome,” Chap. 21). This entire constellation of symptoms is sometimes referred to as the syndrome of the angular gyrus. Anomic aphasia may be added (see later).


Neurology_Adams

Neurology_Adams. This syndrome was mentioned in the earlier discussion on Broca aphasia. As a result of a vascular lesion or other type of localized injury of the dominant frontal lobe, the patient loses all capacity to speak while retaining perfectly the ability to write, to understand spoken words, to read silently with comprehension, and to repeat spoken words. Right facial and brachial paresis may be associated. From the time speech becomes audible, language may be syntactically complete, showing neither loss of vocabulary nor agrammatism; or there may be varying degrees of dysarthria (hence “cortical dysarthria”), anomia, and paraphasic substitutions, especially for consonants. The most notable feature of this type of speech disorder is its transience; within a few weeks or months, language is restored to normal. Bastian, Broca, and more recently other authors called this syndrome aphemia, a term that was used originally by Broca in another context to describe the severe motor aphasia that now


Neurology_Adams

Neurology_Adams. to normal. Bastian, Broca, and more recently other authors called this syndrome aphemia, a term that was used originally by Broca in another context to describe the severe motor aphasia that now carries his name. Probably the syndrome is closely allied to the “mini-Broca aphasia” described earlier under “Broca Aphasia.”


Neurology_Adams

Neurology_Adams. The anatomic basis of pure word mutism has not been determined precisely. In a few postmortem cases, reference is made to a lesion in the Broca area. Damasio and Geschwind have stated that the lesion is anterior and superior to this area. A well studied case has been reported by LeCours and Lhermitte. Their patient uttered only a few sounds for four weeks, after which he recovered rapidly and completely. From the onset of the stroke, the patient showed no disturbance of comprehension of language or of writing. Autopsy disclosed an infarct that was confined to the cortex and subjacent white matter of the lowermost part of the precentral gyrus; the Broca area, one gyrus forward, was completely spared. Other cases have involved mainly the Broca area. Anomic (Amnesic, Nominal) Aphasia


Neurology_Adams

Neurology_Adams. Some degree of word-finding difficulty is part of almost every type of language disorder, including that which occurs with the confusional states and dementia. In fact, without an element of anomia, a diagnosis of aphasia is usually incorrect. Only when this feature is the most notable aspect of language difficulty is the term anomic aphasia employed. In this condition, a relatively uncommon form of aphasia in pure form, the patient loses only the ability to name people and objects. There are pauses in speech, groping for words, circumlocution, and substitution of another word or phrase that is intended to convey the meaning. Perseveration may be prominent. Or the patient may simply fail to name a shown object, in contrast to the usual aphasic patient, who produces a paraphasic error. Less frequently used words give more trouble. When shown a series of common objects, the patient may tell of their use, or demonstrate the same, instead of giving their names. The difficulty applies not


Neurology_Adams

Neurology_Adams. frequently used words give more trouble. When shown a series of common objects, the patient may tell of their use, or demonstrate the same, instead of giving their names. The difficulty applies not only to objects seen but also to the names of things heard or felt (as per Geschwind). In addition to displaying normal fluency of spontaneous speech and preserved comprehension and repetition, the patients we have seen with anomic aphasia have been surprisingly adept in spelling.


Neurology_Adams

Neurology_Adams. Beauvois and coworkers have described a form of bilateral tactile aphasia caused by a left parietooccipital lesion in which objects seen and verbally described could be named, but not those felt with either hand. Recall of the names of letters, digits, and other printed verbal material is almost invariably preserved, and immediate repetition of a spoken name is intact. That the deficit is principally one of naming is shown by the patient’s correct use of the object and, usually, by an ability to point to the correct object on hearing or seeing the name and to choose the correct name from a list. The patient’s understanding of what is heard or read is normal.


Neurology_Adams

Neurology_Adams. There is a tendency for patients with anomia to attribute their failure to forgetfulness or to give some other implausible excuse for the disability, suggesting that they are not completely aware of the nature of their difficulty, but some are aware of the defect. Of course, there are many more patients who fail not only to name objects but also to recognize the correct word when it is given to them. In such patients, the understanding of what is heard or read is not normal, i.e., the naming difficulty is but one symptom of another type of aphasic disorder.


Neurology_Adams

Neurology_Adams. Anomic aphasia has been associated with lesions in different parts of the language area, typically in the left temporal lobe. In these cases, the lesion has been deep to the posterior temporal lobe, particularly in the left thalamus, or in the middle temporal convolution, in a location to interrupt connections between sensory language areas and the hippocampal regions concerned with learning and memory. Mass lesions, such as a tumor, herpes encephalitis, or an abscess, are the most frequent causes; as these lesions enlarge, a contralateral upper quadrantic visual field defect or a Wernicke aphasia is added. Occasionally, anomia appears with lesions caused by occlusion of the temporal branches of the posterior cerebral artery, and it is in these instances that we have seen the most pronounced cases of anomia, usually associated with a right hemianopia and alexia but normal writing ability. Anomia may be a prominent manifestation of transcortical motor aphasia (see later) and may be


Neurology_Adams

Neurology_Adams. cases of anomia, usually associated with a right hemianopia and alexia but normal writing ability. Anomia may be a prominent manifestation of transcortical motor aphasia (see later) and may be associated with the Gerstmann syndrome, in which case the lesions are found in the frontal lobe and angular gyrus, respectively.


Neurology_Adams

Neurology_Adams. An anomic type of aphasia is often an early sign of Alzheimer and Pick disease (minor degrees of it are common in old age) and is a principal feature of one type of degenerative lobar cerebral atrophy in the category of the primary progressive aphasias (see Chap. 39). Finally, anomic aphasia may be the only residual abnormality after partial recovery from Wernicke, conduction, transcortical sensory, or (rarely) Broca aphasia (Benson).


Neurology_Adams

Neurology_Adams. This rare and somewhat amusing condition defies classification but is worthy of comment because it may be mistaken for hysteria or psychosis. An accent that is distinctly foreign but vague in actual region of origin replaces the patient’s native speech pattern. The syndrome arises after a left-sided lesion, most often a stroke with a mild associated Broca aphasia. Although the accent may be interpreted by the listener as compatible with German, Spanish, French, Asian, or another nationality, authoritative analysis indicates that the alterations are not specific to any genuine language and are simply attributed by the listener to a known foreign accent. The syndrome is also encountered as a transient phenomenon during recovery from stroke. The relation to disorders of prosody, which is produced by lesions of the nondominant hemisphere, is unclear. LeCours and Lhermitte made an analysis of the disorder based on the obligate use of diphthongs in certain languages; these were not properly


Neurology_Adams

Neurology_Adams. by lesions of the nondominant hemisphere, is unclear. LeCours and Lhermitte made an analysis of the disorder based on the obligate use of diphthongs in certain languages; these were not properly pronounced in the foreign accent syndrome and made French listeners detect an English accent. An extensive examination of one case and references to additional ones can be found in the article by Kurowski and colleagues.


Neurology_Adams

Neurology_Adams. Writing is, of course, an integral part of language function, but a less essential and universal component, for a segment of the world’s population speaks but does not read or write. It might be supposed that all the rules of language derived from the study of aphasia would be applicable to agraphia. In large part, this is true. One must be able to formulate ideas in words and phrases in order to have something to write as well as to say; hence, disorders of writing, like disorders of speaking, reflect all the basic defects of language. But there is an obvious difference between these two expressive modes. In speech, only one final motor pathway coordinating the movements of lips, tongue, larynx, and respiratory muscles is available, whereas if the right hand is paralyzed, one can still write with the left one, or with a foot, and even with the mouth by holding a pencil between the teeth (a contrivance used by individuals whose arms are paralyzed by cervical root avulsion from


Neurology_Adams

Neurology_Adams. still write with the left one, or with a foot, and even with the mouth by holding a pencil between the teeth (a contrivance used by individuals whose arms are paralyzed by cervical root avulsion from motorcycle accidents). An accurate general statement is that written language is disordered similarly to spoken language in the Broca and Wernicke aphasias and in most of their derivatives. When comprehension is impaired, writing to dictation is often impossible. Paraphasias appear in the writings of aphasics much the same as they do in speech.


Neurology_Adams

Neurology_Adams. The writing of a word can be accomplished either by the direct lexical method of recalling its spelling or by sounding out its phonemes and transforming them into learned graphemes (motor images), that is, the phonologic method. Some authors state that in agraphia there is a specific difficulty in transforming phonologic information, acquired through the auditory sense, into orthographic forms; others see it as a block between the visual form of phonemes, and the cursive movements of the hand (Basso et al). In support of the latter idea is the fact that reading and writing usually develop together and are long preceded by the development of speech as a means of communication.


Neurology_Adams

Neurology_Adams. Pure agraphia as the initial and sole disturbance of language function is a rarity, but such cases have been described as summarized by Rosati and de Bastiani. Pathologically verified cases are virtually nonexistent, but imaging sometimes discloses a lesion of the posterior perisylvian area. This is in keeping with the observation that a lesion in or near the angular gyrus will occasionally cause a disproportionate disorder of writing as part of the Gerstmann syndrome. As mentioned earlier in the chapter, the notion of specific center for writing in the posterior part of the second frontal convolution (the “Exner writing area”) has been questioned (see Leischner). However, Croisile and associates do cite cases of dysgraphia in which a lesion (in the case they reported, a hematoma) was located in the centrum semiovale beneath the motor parts of the frontal cortex and direct electrical stimulation of the cortex rostral to the primary motor hand area disturbs handwriting without


Neurology_Adams

Neurology_Adams. was located in the centrum semiovale beneath the motor parts of the frontal cortex and direct electrical stimulation of the cortex rostral to the primary motor hand area disturbs handwriting without affecting other language or manual tasks according to Roux and colleagues, a veritable apraxia of writing.


Neurology_Adams

Neurology_Adams. Quite apart from these aphasic agraphias, in which spelling and grammatical errors abound, there are special forms of agraphia caused by abnormalities of spatial perception and praxis. Disturbances in the perception of spatial relationships underlie constructional agraphia. In this circumstance, letters and words are formed clearly enough but are wrongly arranged on the page. Words may be superimposed, reversed, written diagonally or in a haphazard arrangement, or from right to left; in the form associated with right parietal lesions, only the right half of the page is used. Usually one finds other constructional difficulties as well, such as inability to copy geometric figures or to make drawings of clocks, flowers, and maps, etc. This is a common feature of developmental dyslexia.


Neurology_Adams

Neurology_Adams. A third group of writing disorder may be called the apraxic agraphias. Here, language formulation is correct and the spatial arrangements of words are respected, but the hand has lost its skill in forming letters and words. Handwriting becomes a scrawl, losing all personal character. There may be an uncertainty as to how the pen should be held and applied to paper; apraxias (ideomotor and ideational) are present in the right hander. As a rule, other learned manual skills are simultaneously disordered. Speculations as to the basic fault here are discussed in Chap. 3, under “Apraxia and Other Nonparalytic Disorders of Motor Functions,” and in Chap. 21, in relation to the functions of the frontal and parietal lobes.


Neurology_Adams

Neurology_Adams. In addition to the neurologic forms of agraphia, described previously, psychologists have defined a group of linguistic agraphias, subdivided into phonologic, lexical, and semantic types. These linguistic models are based on loss of the ability to write (and to spell) particular classes of words. For example, the patient may be unable to spell pronounceable nonsense words, with preserved ability to spell real words (phonologic agraphia); or there may be preserved ability to write nonsense words but not irregular words, such as island (lexical agraphia); patients with semantic agraphia have difficulty incorporating the proper meaning into the written word, for example, “the moon comes out at knight.” For the most part, these linguistic agraphias have no well-established cerebral localization and only tenuous associations with the classic aphasias, for which reason this subject is of greater interest to linguists and psychologists than to neurologists.


Neurology_Adams

Neurology_Adams. The orthographic qualities of writing deteriorate in many motor disorders such as Parkinson disease, tremors, dystonias, and spasticity, but careful inspection shows that language content is normal. Also worth brief comment is mirror writing, in which script runs in the opposite direction to normal with each letter also being reversed. Some individuals have an unusual facility to produce mirror writing (notably, Leonardo da Vinci) though it has also been reported in developmentally delayed left-handed children. Those few instances in which mirror writing is acquired tend to be transient and incomplete with strokes in various parts of the left hemisphere, or rarely, the right hemisphere or bifrontal lesions (see the review by Schott).