10.14639/0392-100X-N2283
Objective. The bithermal caloric test is commonly used to detect a canal paresis. However, in case of spontaneous nystagmus, this procedure can provide results of non-univocal interpretation. On the other hand, confirming the presence of a unilateral vestibular deficit can help to differentiate between central and a peripheral vestibular involvement. Methods. We studied 78 patients suffering from acute vertigo and showing spontaneous horizontal unidirectional nystagmus. All patients were submitted to bithermal caloric tests, and the results were compared with those obtained using a monothermal (cold) caloric test. Results. We demonstrate the congruence between the bithermal and monothermal (cold) caloric test through mathematical analysis of the results of both tests in patients with acute vertigo and spontaneous nystagmus.Conclusions. We propose to perform the caloric test in the presence of a spontaneous nystagmus using a monothermal cold assuming that the prevalence of the response to the cold irrigation on the side towards which the nystagmus beats is a sign of the presence of pathological unilateral weakness and therefore more likely peripheral in its origin.
text/xml
1827-675X
2283
en
Augusto Pietro Casani
http://creativecommons.org/licenses/by-nc-nd/4.0
ACTA Otorhinolaryngologica Italica
spontaneous nystagmus
The role of vestibular cold caloric tests in the presence of spontaneous nystagmus
Text.Serial.Journal
https://www.actaitalica.it/
43
Vestibology
2023-02-27
2022-08-17
2023-02-28
2023-02-28
56-64
1
Augusto Pietro Casani
2023/02/27
10.14639/0392-100X-N2283
56
Department of Medicine and Surgery, ENT Section, Pisa University Hospital, Pisa, Italy
1827-675X
spontaneous nystagmus
en
64
The role of vestibular cold caloric tests in the presence of spontaneous nystagmus
https://www.actaitalica.it/article/download/2283/919
43
ACTA OTORHINOLARYNGOLOGICA ITALICA 2023;43:56-64; doi: 10.14639/0392-100X-N2283




Vestibology


The role of vestibular cold caloric tests
in the presence of spontaneous nystagmus
Il ruolo del test monotermico freddo in presenza di nistagmo spontaneo
Mauro Gufoni, Augusto Pietro Casani
Department of Medicine and Surgery, ENT Section, Pisa University Hospital, Pisa, Italy


SUMMARY
Objective. The bithermal caloric test is commonly used to detect a canal paresis. However,
in case of spontaneous nystagmus, this procedure can provide results of non-univocal inter-
pretation. On the other hand, confirming the presence of a unilateral vestibular deficit can
help to differentiate between central and a peripheral vestibular involvement.
Methods. We studied 78 patients suffering from acute vertigo and showing spontaneous
horizontal unidirectional nystagmus. All patients were submitted to bithermal caloric tests,
and the results were compared with those obtained using a monothermal (cold) caloric test.
Results. We demonstrate the congruence between the bithermal and monothermal (cold)
caloric test through mathematical analysis of the results of both tests in patients with acute
vertigo and spontaneous nystagmus.
Conclusions. We propose to perform the caloric test in the presence of a spontaneous nys-
tagmus using a monothermal cold assuming that the prevalence of the response to the cold
irrigation on the side towards which the nystagmus beats is a sign of the presence of patho-
logical unilateral weakness and therefore more likely peripheral in its origin.
KEY WORDS: vestibular caloric test, acute vertigo, canal paresis, directional preponderance,
spontaneous nystagmus

RIASSUNTO
Obiettivo. Il test calorico bitermico è comunemente usato per rilevare una riduzione
                                                                                                    Received: August 17, 2022
dell’attività di un singolo labirinto. Tuttavia, in caso di nistagmo spontaneo, questa proce-
                                                                                                    Accepted: October 3, 2022
dura potrebbe fornire risultati di non univoca interpretazione. D’altra parte, la conferma
della presenza di un deficit vestibolare unilaterale potrebbe aiutare a differenziare tra un
                                                                                                    Correspondence
coinvolgimento vestibolare centrale e uno periferico.
                                                                                                    Augusto Pietro Casani
Metodi. Abbiamo studiato 78 pazienti affetti da vertigine acuta e che mostravano un ni-             Department of Medicine and Surgery, ENT Section,
stagmo spontaneo orizzontale unidirezionale. Tutti i pazienti sono stati sottoposti al test         Pisa University Hospital, via Paradisa 2, 56124
calorico bitermico, i cui risultati sono stati confrontati con quelli ottenuti attraverso un test   Pisa, Italy
calorico monotermico freddo (ice water test).                                                       Tel. +39 050 997499
Risultati. Attraverso un’analisi matematica dei risultati di entrambi i test in una serie           E-mail: augusto.casani@unipi.it
consecutiva di pazienti con vertigine acuta e nistagmo spontaneo, la congruenza tra il test
calorico bitermico e quello monotermico freddo può essere dimostrata.                                 How to cite this article: Gufoni M, Casani
Conclusioni. Si propone di eseguire il test calorico in presenza di un nistagmo spontaneo,            AP. The role of vestibular cold caloric tests in
utilizzando uno stimolo monotermico freddo, considerando che la prevalenza della risposta             the presence of spontaneous nystagmus. Acta
alla prova fredda sul lato verso cui batte il nistagmo sia indicativo della presenza di deficit       Otorhinolaryngol Ital 2023;43:56-64. https://
labirintico monolaterale.                                                                             doi.org/10.14639/0392-100X-N2283

PAROLE CHIAVE: test calorico, vertigine acuta, preponderanza direzionale,                           © Società Italiana di Otorinolaringoiatria
preponderanza labirintica, nistagmo spontaneo                                                       e Chirurgia Cervico-Facciale


                                                                                                                   OPEN ACCESS

                                                                                                    This is an open access article distributed in accordance with
Introduction                                                                                        the CC-BY-NC-ND (Creative Commons Attribution-Non-
                                                                                                    Commercial-NoDerivatives 4.0 International) license. The
The bithermal caloric test is most suitable for identifying unilateral lesions                      article can be used by giving appropriate credit and mentio-
                                                                                                    ning the license, but only for non-commercial purposes and
of the peripheral vestibular system as it allows the independent evaluation of                      only in the original version. For further information: https://
each ear. The standard caloric stimulus is performed by irrigating the external                     creativecommons.org/licenses/by-nc-nd/4.0/deed.en




56
                                                                                                          Vestibular cold caloric test




ear canal with 250 mL of water for 30 seconds. The water          Materials and methods
temperature is 30°C for cool irrigation and 44°C for warm
                                                                  A cohort of 78 patients was considered (41 males and 37
irrigation. Abnormal responses are recorded as canal pare-
                                                                  females; ages ranging from 20 to 88 years, mean 55 years),
sis or directional preponderance 1. However, when a spon-
                                                                  all suffering from acute vertigo and presenting a spontane-
taneous nystagmus is present, this procedure may yield re-
                                                                  ous horizontal unidirectional nystagmus. All patients under-
sults of non-univocal interpretation while simultaneously
                                                                  went bithermal caloric tests using the Fitzgerald-Hallpike
exposing the patient to an unpleasant sensation. The avail-       technique. The external auditory canal was separately irri-
ability of a one-temperature caloric test would shorten the       gated with 125 ml of warm (44°C) and cold (30°C) water in
time required to complete vestibular function assessment          a 30-second period, with a 7-min interval between the two
while mitigating any discomfort experienced by the patient        tests. Responses were recorded by an infrared eye-tracking
during caloric testing. Moreover, confirming the presence         system (GN Otometrics, Taastrup, Denmark), which is able
of a unilateral vestibular deficit may help to differentiate      to automatically extract both the mean frequency and the
between a central and a peripheral vestibular involvement.        mean Slow Phase Velocity (SPV) of the thermally induced
Acute peripheral vertigo (APV) is one of the most common          nystagmus. In accordance with Jongkees’ formulae, the
causes of peripheral vestibular involvement 2, accounting         software then calculates the degree of Canal Paresis (CP)
for 2.5% of emergency healthcare visits 3. Nevertheless,          based on both frequency (freqCP) and SPV (spvCP). Ac-
focal cerebellar stroke, especially in the posterior-inferior     cording to the authors’ experience, CP values > 25% can
cerebellar artery (PICA) area of vascularisation, may mim-        be considered pathological (pathological CP), while values
ic APV, with acute vertigo being the only presenting symp-        between 15% and 25% may be potentially significant (bor-
tom 4,5, the so-called pseudo-APV 6. Between 5 and 25%            derline CP). The Jongkees’ formulae were used to obtain
of isolated dizziness may be related to a posterior fossa         the values of canal paresis and directional preponderance:
infarction 3,6,7, with a reported initial misdiagnosis rate of    the congruence with the results obtained algebraically can
up to 28% 8.                                                      also be verified experimentally. The cold caloric test was
The HINTS examination (Head Impulse test, Nystagmus,              performed as follows: while the patient was lying in the
Test of Skew) is now widely recommended to diagnose               supine position with the head inclined by 30°, the patient’s
acute vestibular syndrome (AVS) of central origin and             head was rotated to the left side (90°) and the external ear
differentiate it from more common peripheral vestibular           canal was irrigated with 2-3 ml of cold water (melted with
diseases. When properly performed, clinical examination           three ice cubes in order to maintain water temperature be-
based on HINTS is more sensitive in identifying small pos-        tween 1 and 3°C) 16. After 30 seconds, the patient straight-
terior circulation strokes causing isolated acute vertigo than    ens the head and following an additional 30 seconds the
early diffusion-weighted MRI imaging 9. In order to train         vestibular response was assessed (in terms of frequency,
emergency physicians to correctly diagnose a central cause        total number of nystagmus beats, and angular velocity of
of AVS, other protocols have been proposed: the STAND-            the slow phase in the stiffness phase) (Fig. 1). After 10 min-
ING (SponTAneous, Nystagmus Direction, head Impulse               utes, the test was repeated on the contralateral side.
Test) in 2014 10, the TiTrATE paradigm (timing, triggers
and targeted bedside examination) 11 and, more recently,          Results
the ATTEST approach (associated symptoms, timing and              In 36 patients, the spontaneous nystagmus was directed
triggers, examination signs and testing) 12. None of the pro-     rightwards, while in 42 patients it was directed leftwards.
posed protocols or algorithms for the evaluation of AVS           A total of 63 patients received a diagnosis of Acute Unilat-
have included caloric testing, although a unilateral weak-        eral Vestibulopathy (AUV), while 4 were diagnosed with
ness to caloric stimuli could significantly impact differen-      Menière’s Disease. In 8 patients, acute vertigo was a con-
tial diagnosis 13. On the other hand, in the presence of spon-    sequence of a central vestibular involvement: 6 cases of
taneous nystagmus, classic bithermal tests may be difficult       vertebro-basilar insufficiency (4 of these patients showed
to interpret and may not be recommended 13,14. The main           signs of white matter lesions on MRI), one case of Wal-
purpose of this study is to evaluate the possibility of detect-   lemberg syndrome and one patient suffering from systemic
ing a pathological unilateral weakness in the presence of         vasculitis with CNS involvement. Finally, 3 patients were
spontaneous nystagmus using only a caloric cold test (ice         diagnosed with vestibular migraine. The results of the bith-
water test) 15 and to recommend the use of this procedure in      ermal caloric test and ice water test are reported in Table I.
the differential diagnosis of APV from central nervous sys-       In all cases, the cold caloric test provided coherent results
tem (CNS) diseases that may present as an isolated vertigo.       with the values of canal paresis and directional prepon-



                                                                                                                                  57
M. Gufoni, A.P. Casani




Figure 1. Monoaural cold test. 1-2) the patient is instructed to lie in the semi-recumbent position with the head tilted forward 30 degrees; 3) approximately 2
ml of ice water is injected into the ear canal via syringe and kept in that position for 30 seconds; 4) the patient’s head is then turned midline and observed for
nystagmus while the patient performs alerting tasks. After 5 minutes, the test is repeated on the contralateral side.


derance and brisker responses than bithermal tests: if the                         (With the condition rw + rc + lw + lc ≠ 0); uw unilateral
spontaneous nystagmus was directed to the right side and                           weakness, dp directional preponderance, rw right warm, lw
the cold test had produced a greater response on the right                         left warm, rc right cold, lc left cold).
ear than the left, then canal paresis exceeded directional                         If the caloric nystagmus beats towards the opposite direc-
preponderance (being therefore pathological), making                               tion (it goes to the right instead of the left or vice versa), it
the spontaneous nystagmus more likely to be peripheral.                            is represented with a negative sign.
In all cases, the directional preponderance was congruent                          In this example, a spontaneous nystagmus directed to the
with the spontaneous nystagmus (positive if the sponta-                            right is considered.
neous nystagmus was directed to the right and negative if
the spontaneous nystagmus was directed to the left). The                           Demonstration
congruence with the results obtained algebraically has also                        Working hypotheses:
been verified experimentally.                                                      Hypothesis 1)
With the above-described procedure, two values could be                            dp ≠ 0, because if there is a spontaneous nystagmus it is as-
obtained:                                                                          sumed that there is also a pathological directional prepon-
• the response of cold stimulation on the right (rc); and                          derance; therefore (rw + lc) - (lw + rc) ≠0 (the numerator
• the response of cold stimulation on the left (lc).                               of the formula for dp is non-zero); dp must also be positive
These results can be used to assess the presence of a patho-                       in the hypothesis that the nystagmus beats to the right.
logical canal paresis (CP).
                                                                                   Hypothesis 2)
Demonstration                                                                      • rw > 0 (warm stimulation of the right ear cannot reason-
Premise:                                                                              ably inhibit or reverse nystagmus if it is directed right-
                                                                                      wards);
                                                                                   • lc > 0 (cold stimulation of the left ear cannot reasonably
                                                                                      inhibit or reverse nystagmus if it is directed rightwards).
                                                                                   Consequently, rw + lc > 0 (the sum of two positive numbers
                                                                                   is positive).



58
                                                                                                                                          Vestibular cold caloric test




Table I. The results of monothermal cold tests and the values of Canal Paresis (CP) and Directional Preponderance (DP) evaluated with bithermal caloric test.
The last two columns highlight the fact that there is always agreement between the cold test that gives the greatest response and the values of CP and DP: if the
spontaneous nystagmus beats to the right and the cold right test gives a greater response than the cold left, then there is certainly a canal paresis greater than the
directional preponderance (therefore pathological) making spontaneous nystagmus more likely to be peripheral. In all cases, DP was congruent with the spontane-
ous nystagmus (positive if the spontaneous nystagmus was directed to the right and negative if the spontaneous nystagmus was directed to the left). Note cases
36 and 78 in which, the cold tests being symmetrical, the labyrinthine preponderance was equal to the directional preponderance.
 Right beating spontaneous nystagmus
            Age         Gender                Diagnosis                 RC              LC             CP             DP                   Congruence
1           68            M                      AUV                      0             12            43.8          118.8          R<L            CP < DP
2           65            M                      AUV                     13             41             7.6           54.6          R<L            CP < DP
3           68            F                      AUV                      0             58            -6.2           83.1          R<L            CP < DP
4           64            F                      VM                      36             45             1.0           10.0          R<L            CP < DP
5           38            M                      AUV                     15             21            74.4           88.4          R<L            CP < DP
6           23            M                      AUV                     27             32            75.3           86.5          R<L            CP < DP
7           80            M                      AUV                     -9             25           118.5          244.4          R<L            CP < DP
8           63            F                      AUV                      5             12            84.2          121.1          R<L            CP < DP
9           37            F                      AUV                      0             38           108.3          266.7          R<L            CP < DP
10          38            F                      AUV                      0             28           100.0          240.0          R<L            CP < DP
11          84            F                      AUV                      0             13           100.0          188.3          R<L            CP < DP
12          47            M                      AUV                     22             32            58.2           80.2          R<L            CP < DP
13          65            F                      AUV                     0              25            90.0          215.0          R<L            CP < DP
14          52            M                      AUV                     0              30            25.0          100.0          R<L            CP < DP
15          61            M                      AUV                     0              20           100.0          197.6          R<L            CP < DP
16          59            M                      AUV                     0              20             4.8           68.3          R<L            CP < DP
17          24            F                      AUV                    -27             50            54.8          545.2          R<L            CP < DP
18          66            M                      VBI                    21              31            67.6          102.6          R<L            CP < DP
19          29            F                      AUV                     0              37             9.8          100.0          R<L            CP < DP
20          48            F                     WALL                    42              60             0.9           17.9          R<L            CP < DP
21          67            F                      AUV                    15              25            45.7           67.4          R<L            CP < DP
22          70            M                      AUV                     0              30           -22.2           44.4          R<L            CP < DP
23          47            F                      AUV                     0              40           66.7           200.0          R<L            CP < DP
24          37            F                      AUV                     0              25           29.6           100.0          R<L            CP < DP
25          49            F                      AUV                     0              20           70.7           168.3          R<L            CP < DP
26          55            F                      AUV                    21              26           22.9           34.9           R<L            CP < DP
27          88            F                      VBI                    32              38           26.2           37.9           R<L            CP < DP
28          82            F                      AUV                    11              12           61.9           65.1           R<L            CP < DP
29          59            F                      AUV                    56              20           59.7            7.9           R>L            CP > DP
30          63            M                      AUV                    43              18           56.0           10.1           R>L            CP > DP
31          80            M                      AUV                    22              13           61.2           34.3           R>L            CP > DP
32          53            F                      AUV                    47              45            8.0            6.1           R>L            CP > DP
33          65            M                      AUV                    24              18           60.0           46.6           R>L            CP > DP
34          62            F                       SV                    30              27           20.7           15.7           R>L            CP > DP
35          51            F                      VM                     22              21           15.5           13.8           R>L            CP > DP
36          54            M                      AUV                    47              47           10.9           10.9           R=L            CP = DP
Left beating spontaneous nystagmus
37           68            M                     AUV                     53             44           -24.8           33.7          L<R               CP < DP
38           29            M                     MD                      50             46           -11.5           16.1          L<R               CP < DP
39           55            F                     MD                      47              9            22.0           54.0          L<R               CP < DP
40           63            M                     AUV                     30             16           -30.2           62.8          L<R               CP < DP
                                                                                                                                                         continues u



                                                                                                                                                                  59
M. Gufoni, A.P. Casani




Table I. The results of monothermal cold tests and the values of Canal Paresis (CP) and Directional Preponderance (DP) evaluated with bithermal caloric test.
The last two columns highlight the fact that there is always agreement between the cold test that gives the greatest response and the values of CP and DP: if the
spontaneous nystagmus beats to the right and the cold right test gives a greater response than the cold left, then there is certainly a canal paresis greater than the
directional preponderance (therefore pathological) making spontaneous nystagmus more likely to be peripheral. In all cases, DP was congruent with the spontane-
ous nystagmus (positive if the spontaneous nystagmus was directed to the right and negative if the spontaneous nystagmus was directed to the left). Note cases
36 and 78 in which, the cold tests being symmetrical, the labyrinthine preponderance was equal to the directional preponderance (follows).
 Left beating spontaneous nystagmus
             Age          Gender                  Diagnosis                     RC               LC              CP              DP                     Congruence
 41          43             M                        VM                         15                5             -3.6            39.3           L<R             CP < DP
 42          51             F                        AUV                        42                0              2.4           100.0           L<R             CP < DP
 43          45             F                        AUV                        16               11           -100.0           123.3           L<R             CP < DP
 44          62             M                        AUV                        34                0            -19.0           100.0           L<R             CP < DP
 45          46             F                        MD                         47              -10             35.4            79.8           L<R             CP < DP
 46          67             F                        AUV                        36                0            -34.9           121.7           L<R             CP < DP
 47          48             F                        AUV                        14                0            -79.5           151.3           L<R             CP < DP
 48          72             M                        AUV                        43                0             -1.0            87.0           L<R             CP < DP
 49          63             F                        VBI                        14                0            -17.6           100.0           L<R             CP < DP
 50          59             M                        AUV                        30               18            106.1           142.4           L<R             CP < DP
 51          52             F                        AUV                        25              -15            -31.7           226.8           L<R             CP < DP
 52          35             F                        AUV                        30                0            -47.4           152.6           L<R             CP < DP
 53          87             F                        VBI                        36                0             -5.3           100.0           L<R             CP < DP
 54          48             M                        AUV                        15              10             -87.0           108.7           L<R             CP < DP
 55          67             M                        AUV                        41                0            -93.3           230.0           L<R             CP < DP
 56          33             M                        AUV                        37                0           -103.6           238.2           L<R             CP < DP
 57          69             M                        VBI                        40                0              -7            100.0           L<R             CP < DP
 58          50             M                        MD                         17                0            -67.2           117.9           L<R             CP < DP
 59          20             F                        AUV                        15              12             -56.5            65.2           L<R             CP < DP
 60          29             F                        AUV                        40               0             -72.4           210.3           L<R             CP < DP
 61          40             M                        AUV                        36               9              -4.9            57.3           L<R             CP < DP
 62          67             F                        AUV                        20               0             -44.4           100.0           L<R             CP < DP
 63          30             F                        AUV                        23              27             -70.7           61.0            L>R             CP > DP
 64          55             M                        AUV                        38              40             -22.4           20.9            L>R             CP > DP
 65          71             F                        AUV                        18              31             -97.7           67.4            L>R             CP > DP
 66          35             M                        AUV                        40              42             -14.8           12.4            L>R             CP > DP
 67          48             M                        AUV                        18              28             -37.2           20.7            L>R             CP > DP
 68          65             M                        AUV                         0              25            -100.0            7.4            L>R             CP > DP
 69          47             M                        AUV                        28              31             -58.1           52.4            L>R             CP > DP
 70          44             M                        AUV                         7               8            -100.0           93.3            L>R             CP > DP
 71          65             M                        AUV                        25              31             -51.5           39.8            L>R             CP > DP
 72          41             M                        AUV                         0              30            -187.5           62.5            L>R             CP > DP
 73          72             M                        VBI                         6              16             -82.4           52.9            L>R             CP > DP
 74          73             F                        AUV                         0              21            -100.0           26.3            L>R             CP > DP
 75          60             M                        AUV                        11              17            -106.9           86.2            L>R             CP > DP
 76          45             M                        AUV                        12              20             -77.6           45.9            L>R             CP > DP
 77          62             M                        AUV                        38              40             -14.9           12.6            L>R             CP > DP
 78          70             M                        AUV                        15              15             -55.2           55.2            L=R             CP = DP
RC: Right Cold test, number of the nystagmus beats at culmination; LC: Left Cold test, number of the nystagmus beats at culmination; M: male; F: female; AUV: Acute Unilateral Vesti-
bulopathy; VM: Vestibular Migraine; Wall: Wallemberg syndrome; VBI: Vertebro-Basilar Insufficiency; SV: Systemic Vasculitis with CNS involvement; MD: Menière’s disease.




60
                                                                                                          Vestibular cold caloric test




Demonstration
Calculations
If the directional preponderance is strictly positive (hy-
pothesis 1):
                                                                 or:


This is true in two cases:
                                                                 (both denominators are strictly positive: point b).
a)                                                               Simplifying:

or:

b)
Case a)
 Adding member to member (two negative numbers will
generate another negative number), so:
(rw + lc) - (lw + rc) + rw + lw + rc + lc < 0
rw + lc - lw - rc + rw + lw + rc + lc < 0 (-lw and +lw cancel    and since the denominator is positive, the numerator must
                                                                 also be positive (or equal to 0).
each other out, as -rc and +rc)
                                                                 So:
rw + lc + rw + lc < 0
2 * (rw + lc) < 0
rw + lc < 0 (this is not acceptable according to hypothesis 2)
Case b)
Adding member to member (two positive numbers) another           The mathematical steps are all reversible so that the follow-
positive number should result, so:                               ing can be concluded.
(rw + lc) - (lw + rc) + rw + lw + rc + lc > 0                    In the case of a nystagmus directed to the right, if unilateral
                                                                 weakness is greater than the directional preponderance, the
rw + lc - lw - rc + rw + lw + rc + lc > 0 (-lw and +lw cancel
                                                                 cold right stimulus should produce stronger responses than
each other out, as -rc and +rc)
                                                                 the cold left.
rw + lc + rw + lc > 0
                                                                 In the case of a nystagmus directed to the right, if the cold
2 * (rw + lc) > 0
                                                                 right response is brisker than the cold left, unilateral weak-
rw + lc > 0 (which is in accordance with hypothesis 2)           ness predominates over directional preponderance.
Hypothesis a) is excluded and only hypothesis b) is consid-      The above conclusions are valid regardless of the nystag-
ered valid, which provides:                                      mus dimension considered [frequency and slow phase ve-
                                                                 locity (SPV)].
b)
                                                                 Discussion
If dp is pathological (hypothesis 1) and uw ≥ dp, then uw is
also pathological (normal values are of the same order of        The presence of a canal paresis in the acute phase of a ver-
magnitude and almost the same in all laboratories) and the       tiginous attack may point towards a vertigo of peripheral
nystagmus is more likely of peripheral origin.                   origin, although this finding alone is not sufficient for a
                                                                 complete differential diagnosis. Nevertheless, it represents
                                                                 an important indicator that, together with other clinical and
                                                                 instrumental data, may be useful in distinguishing periph-
                                                                 eral vestibular involvement from central involvement 5.
                                                                 The presence of a spontaneous nystagmus makes it difficult
It can be divided by dp first and second member of the in-       to perform and interpret a bithermal caloric test which is
equality because dp > 0 (hypothesis 1).                          therefore generally not recommended. A recent study rec-
We may replace the Jongkees’ formulas:                           ommends abandoning caloric testing and replacing it with



                                                                                                                                  61
M. Gufoni, A.P. Casani




video Head Impulse Test (vHIT) in the acute setting 14.                           2. If the cold right response is equal to the cold left re-
On the contrary, the present study may confirm the use-                              sponse, then the labyrinthine preponderance is equal to
fulness of caloric testing if performed using the simplified                         the directional preponderance, and since a spontaneous
method (monothermal cold caloric tests), while consid-                               nystagmus is present, the directional preponderance can
ering that an asymmetric caloric response can also occur                             be considered pathological. Therefore, the labyrinthine
with central vestibular pathologies. Moreover, vHIT and                              preponderance is also pathological, which implies that
other advanced pieces of equipment may not be available                              the nystagmus is more probably peripheral in origin.
in all clinical settings (especially in the Emergency Room).                      3. If the right cold response is less evident than the left
Indeed, the application of cold caloric tests alone in most                          cold, it is only possible to say that the unilateral weak-
cases does allow the determination of whether a canal pare-                          ness is less relevant than the directional preponderance;
sis is present, though it does not measure the percentage of                         however, this finding is not determinant for the differen-
its impairment (information that is not strictly necessary).                         tial diagnosis.
The algorithm presented in Figure 2 provides an example.                          In fact:
1. If the cold thermal stimulation generates a greater re-
                                                                                  Example 1
   sponse on the right side than the left, the spontaneous
                                                                                  uw = 30; dp = 40
   nystagmus (directed to the right) is more likely to be
                                                                                  (There is a pathological unilateral weakness, even if less
   peripheral in origin, or, at least, a pathological labyrin-
                                                                                  than the directional preponderance, uw < dp: more likely
   thine preponderance is present. The same process can
                                                                                  peripheral nystagmus).
   be applied in terms of sign symmetry, in the case of a
   left-directed nystagmus: if the left cold response is more                     Or:
   intense than the right, a pathological labyrinthine pre-                       Example 2
   ponderance is present.                                                         uw = 5; dp = 40




Figure 2. Algorithm for diagnosis of pathological labyrinthine preponderance with cold tests only.



62
                                                                                                           Vestibular cold caloric test




(There is no pathological unilateral weakness, but uw < dp:        • to our knowledge there is no demonstration that the sum
more likely central nystagmus).                                       of the two separate cold stimuli is equivalent to the si-
In both cases uw < dp, but the first case is more likely to be        multaneous cold administration;
central in origin, the second case is more likely peripheral.      • the execution of the classic simultaneous cold test can
Therefore, in the event of a right-beating nystagmus, if              be difficult to perform and does not guarantee a perfect
the right cold response is less evident than the left cold re-        symmetry of stimulation; and
sponse, a spontaneous nystagmus directed to the right is to        • in the case of areflexia, only one cold stimulation (of the
be considered at risk of centrality. In the case of partial left      ear towards which the nystagmus beats) is sufficient.
labyrinthine damage, a spontaneous right-directed nystag-          This study has several limitations: the frequency range over
mus is generated in the first hours of the disease when a          which thermal caloric stimuli affect the horizontal canal is
compensatory mechanism has not been established yet. In            at the low end of the physiologic range of stimulation of
this case, by performing a right cold test:                        the semi-circular canals. For this reason, it is possible to
1. the right semi-circular canal is blocked by cold inhibi-        lose low-frequency sensitivity and yet retain middle- and
   tory stimulation; and                                           high-frequency function. This study comprises a consecu-
2. the left semi-circular canal prevails by virtue of its resid-   tive series of patients with acute vertigo and spontaneous
   ual function, thus generating a left-directed nystagmus.        nystagmus: in order to confirm the utility of this test to ex-
While by performing a cold caloric test on the left:               clude central vestibular damage a prospective study should
1. the left semi-circular canal is blocked due to cold inhibi-     be designed. Finally, not all patients were studied with the
   tory stimulation; and                                           video Head Impulse Test (vHIT), which is now considered
2. the right semi-circular canal prevails by virtue of its full    the gold standard for the evaluation of patients suffering
   functionality, generating a nystagmus beating rightwards.       from acute vertigo.
Since the right ear functions better than the left ear, the re-
sponse to the cold stimulus will necessarily be less intense
                                                                   Conclusions
on the right than on the left, as in the initial stages of dis-
ease labyrinthine preponderance will always be inferior to         We propose the execution of the ice water test in patients
directional preponderance.                                         with spontaneous nystagmus to confirm the presence of
As the compensation proceeds, a nystagmus (of compensa-            AUV, avoiding the long and unpleasant procedure of the
tion) directed towards the affected ear (the left in this ex-      bithermal caloric test. The cold caloric test is easy to
ample) is generated, which will progressively decrease the         perform, well tolerated (decreases the amplitude and fre-
difference between the two ears in terms of cold response,         quency of the spontaneous nystagmus) and can be used in
until the cold left response will become preponderant com-         any working environment (Emergency Department, Out-
pared to the cold right. In other words, as the compensation       patient Department and even at the patient’s house). Fur-
proceeds, the directional preponderance tends to decrease.         thermore, this procedure can be useful (when combined
The cold caloric test cannot be considered an alternative          with any other clinical, HINTS, and instrumental, vHIT,
to the clinical head impulse test. In fact, the two tests ex-      protocols) to confirm the occurrence of a canal paresis,
plore different frequencies and are not comparable from a          thus pointing towards a peripheral origin of the spontane-
pathophysiological point of view: it is not uncommon for           ous nystagmus.
the results of bithermal caloric tests and vHITs to differ
significantly in patients with AUV and in some cases of            Conflict of interest statement
Menière’s Disease 17-19. For this reason, we propose the cold      The authors declare no conflict of interest.
test alongside the classical HINTs tests (including HIT).
Indeed, the differential diagnosis of an acute vertigo pre-        Funding
senting with a spontaneous nystagmus is obtained by the            This research did not receive any specific grant from fund-
interpretation of a wide plethora of tests, each contributing      ing agencies in the public, commercial, or not-for-profit
to the final clinical picture.                                     sectors.
The ice water test can be performed simultaneously on both
ears, as previously described 20. However, in the presence of      Author contributions
a spontaneous nystagmus, the authors of the present study          MG: study concept and design, acquisition of data, analysis
do not believe that this test can provide results equivalent       and interpretation of data, study supervision; APC: study
to the binaural cold test. The two separate cold stimuli were      concept and design, analysis, and interpretation of data,
chosen for multiple reasons:                                       drafting of the manuscript, study supervision.



                                                                                                                                   63
M. Gufoni, A.P. Casani




Ethical consideration                                                           9
                                                                                     Kattah JC, Talkad AV, Wang DZ, et al. HINTS to diagnose stroke
Ethical review and approval by the local Institutional Board                         in the acute vestibular syndrome: three-step bedside oculomo-
                                                                                     tor examination more sensitive than early MRI diffusion-weight-
(Comitato Etico Azienda Ospedaliero-Universitaria Pisana,                            ed imaging. Stroke 2009;40:3504-3510. https://doi.org/10.1161/
Pisa, Italy) were waived for this study. Due to its retrospec-                       strokeaha.109.551234
tive nature, it was not considered as part of a research pro-                   10
                                                                                     Vanni S, Pecci R, Edlow JA, et al. Differential diagnosis of verti-
ject. Furthermore, the study does not include new invasive                           go in the emergency department: a prospective validation study of
or experimental procedures or diagnostic protocol; all pa-                           the STANDING algorithm. Front Neurol 2017;8:590. https://doi.
                                                                                     org/10.3389/fneur.2017.00590
tients underwent routinely performed tests only, according
to national guidelines. Informed consent was obtained from
                                                                                11
                                                                                     Newman-Toker DE, Edlow JA. TiTrATE: a novel, evidence-based
                                                                                     approach to diagnosing acute dizziness and vertigo. Neurol Clin
all participants and the study was performed in accordance                           2015;33:577-599. https://doi.org/10.1016/j.ncl.2015.04.011
with the Declaration of Helsinki.                                               12
                                                                                     Edlow JA, Gurley KL, Newman-Toker DE. A new diagnostic approach
                                                                                     to the adult patient with acute dizziness. J Emerg Med 2018;54:469-
References                                                                           483. https://doi.org/10.1016%2Fj.jemermed.2017.12.024
                                                                                13
                                                                                     British Society of Audiology. Recommended procedure: the Caloric
1
     Shepard NT, Jacobson GP. The caloric irrigation test. Hand                      Test. Br J Audiol 1999;33:179-184.
     Clin      Neurol       2016;137:119-131.        https://doi.org/10.1016/
     B978-0-444-63437-5.00009-1
                                                                                14
                                                                                     Morrison M, Korda A, Zamaro E, et al. Paradigm shift in acute dizzi-
                                                                                     ness: is caloric testing obsolete? J Neurol 2021:269:853-860. https://
2
     Kerber KA. Acute vestibular syndrome. Semin Neurol 2020;40:59-
     66. https://doi.org/10.1055/s-0039-3402739                                      doi.org/10.1007/s00415-021-10667-7
3
     Kerber KA, Meurer WJ, West BT, et al. Dizziness presentations in U.S.
                                                                                15
                                                                                     Jacobson GP, Newman CW. Background and technique of caloric
     emergency departments, 1995-2004. Acad Emerg Med 2008;15:744-                   testing. In: Jacobson GP, Newman CW, Kartoush JM, editors. Hand-
     750. https://doi: 10.1111/j.1553-2712.2008.00189                                book of Balance function testing. St Louis, MO: Mosby Year Book;
4
     Edlow JA, Newman-Toker DE, Savitz SI. Diagnosis and initial man-                1993. p. 156.
     agement of cerebellar infarction. Lancet Neurol 2008;7:951-964.            16
                                                                                     Nelson JR. The minimal ice water test. Neurology 1969;19:577-585.
     https://doi.org/10.1016/s1474-4422(08)70216-3                                   https://doi.org/10.1212/wnl.19.6.577
5
     Lee H, Sohn SI, Cho YW, et al. Cerebellar infarction present-              17
                                                                                     Lee JY, Kwon E, Kim HJ, et al. Dissociated results between caloric
     ing isolated vertigo: frequency and vascular topographical pat-                 and video head impulse tests in dizziness: prevalence, pattern, lesion
     terns. Neurology 2006;67:1178-1183. https://doi.org/10.1212/01.                 location, and etiology. J Clin Neurol 2020;16:277-284. https://doi.
     wnl.0000238500.02302.b4                                                         org/10.3988%2Fjcn.2020.16.2.277
6
     Casani AP, Dallan I, Cerchiai N, et al. Cerebellar infarctions             18
                                                                                     Hannigan IP, Welgampola MS, Watson SRD. Dissociation of calor-
     mimicking acute peripheral vertigo: how to avoid misdiagno-
                                                                                     ic and head impulse tests: a marker of Meniere’s disease. J Neurol
     sis? Otolaryngol Head Neck Surg 2013;148:475-481. https://doi.
     org/10.1177%2F0194599812472614                                                  2021;268:431-439. https://doi.org/10.1007/s00415-019-09431-9
7
     Norrving B, Magnusson M, Holtas S. Isolated acute vertigo in the el-
                                                                                19
                                                                                     Waissbluth S, Sepúlveda V. Dissociation between caloric and video
     derly: vestibular or vascular disease? Acta Neurol Scand 1995;91:43-            head impulse tests in dizziness clinics. Audiol Res 2022;12:423-432.
     48. https://doi.org/10.1111/j.1600-0404.1995.tb05841.x                          https://doi.org/10.3390/audiolres12040043
8
     Masuda Y, Tei H, Shimizu S, et al. Factors associated with the misdiag-    20
                                                                                     Furman JM, Wall C 3rd, Kamerer DB. Alternate and simultaneous bin-
     nosis of cerebellar infarction. J Stroke Cerebrovasc Dis 2013;22:1125-          aural bithermal caloric testing: a comparison. Ann Otol Rhinol Laryn-
     1130. https://doi.org/10.1016/j.jstrokecerebrovasdis.2012.10.004                gol 1988;97:359-364. https://doi.org/10.1177/000348948809700406




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