10.14639/0392-100X-N1033
Objective. Study the high-frequency vestibulo-oculomotor reflex in posterior canal benign paroxysmal positional vertigo (BPPV) through Video Head Impulse Test (vHIT). Methods. 150 patients suffering for the first time from posterior canal BPPV were studied. Posterior canal vestibulo ocular reflex (VOR) gain was analysed through stimulations in right anterior-left posterior and left anterior-right posterior planes before treatment, immediately after resolution of the acute stage and one month later. Results were compared with a group of 100 healthy individuals. Results. No significant difference between the study the control groups was observed, except for normalised asymmetry ratio of the posterior canal which was significantly higher in the study group. VOR gains of both affected posterior canals and contralateral healthy posterior canals were not significantly correlated with the VOR gain of ipsilateral and contralateral anterior canals. Conclusions. vHIT does not seem to represent an essential tool to study typical posterior canal BPPV in patients affected by this disease for the first time. Different results might be expected in relapsing forms, non-responsive forms, long lasting forms, or atypical variants in which major damage could be provoked by the persistence of otoconia in the canal or by its complete or partial jam.
application/xml
1827-675X
1033
en
Maria Grazia Melillo
https://creativecommons.org/licenses/by-nc-nd/4.0
ACTA Otorhinolaryngologica Italica
vestibulo-oculomotor reflex
The Video Head Impulse Test in the acute stage of posterior canal benign paroxysmal positional vertigo
Text.Serial.Journal
https://www.actaitalica.it/
41
Vestibology
2021-03-19
2020-07-29
2021-03-19
2021-03-24
69-76
1
Maria Grazia Melillo
2021/03/19
10.14639/0392-100X-N1033
69
San Pio Hospital, Department of Audiology and Phoniatrics, Benevento, Italy
1827-675X
vestibulo-oculomotor reflex
76
The Video Head Impulse Test in the acute stage of posterior canal benign paroxysmal positional vertigo
https://www.actaitalica.it/article/download/1033/526
41
ACTA OTORHINOLARYNGOLOGICA ITALICA 2021;41:69-76; doi: 10.14639/0392-100X-N1033




Vestibology


The Video Head Impulse Test in the acute stage
of posterior canal benign paroxysmal positional vertigo
Il Video Head Impulse Test nello stadio acuto della BPPV da canalolitiasi posteriore
Luigi Califano, Raffaella Iannella, Salvatore Mazzone, Francesca Salafia, Maria Grazia Melillo
San Pio Hospital, Department of Audiology and Phoniatrics, Benevento, Italy


SUMMARY
Objective. Study the high-frequency vestibulo-oculomotor reflex in posterior canal benign
paroxysmal positional vertigo (BPPV) through Video Head Impulse Test (vHIT).
Methods. 150 patients suffering for the first time from posterior canal BPPV were studied.
Posterior canal vestibulo ocular reflex (VOR) gain was analysed through stimulations in
right anterior-left posterior and left anterior-right posterior planes before treatment, imme-
diately after resolution of the acute stage and one month later. Results were compared with
a group of 100 healthy individuals.
Results. No significant difference between the study the control groups was observed, ex-
cept for normalised asymmetry ratio of the posterior canal which was significantly higher
in the study group. VOR gains of both affected posterior canals and contralateral healthy
posterior canals were not significantly correlated with the VOR gain of ipsilateral and con-
tralateral anterior canals.
Conclusions. vHIT does not seem to represent an essential tool to study typical posterior
canal BPPV in patients affected by this disease for the first time. Different results might be
expected in relapsing forms, non-responsive forms, long lasting forms, or atypical variants            Received: July 29, 2020
in which major damage could be provoked by the persistence of otoconia in the canal or by              Accepted: November 2, 2020
its complete or partial jam.
KEY WORDS: posterior canal BPPV, vHIT, canalolithiasis, vestibulo-oculomotor reflex                    Correspondence
                                                                                                       Luigi Califano
                                                                                                       via A. Lepore 1, 82100 Benevento, Italy
RIASSUNTO                                                                                              Tel. +39 082 457407. Fax +39 082 457430
Obiettivo. Valutazione del VOR del canale semicircolare posteriore in fase acuta di VPPB               E-mail: luigi.califano@tin.it
da canalolitiasi posteriore.
Metodi. Valutazione del VOR del canale affetto mediante Video-Head Impulse test in 150 pazienti        Funding
per la prima volta affetti da VPPB da canalolitiasi posteriore in fase acuta dopo la diagnosi ma       None.
prima dell’esecuzione della terapia liberatoria, dopo la risoluzione della fase acuta, un mese
dopo la risoluzione. I risultati sono stati confrontati con quelli di un gruppo di 100 persone sane.   Conflict of interest
Risultati. Non sono state riscontrate significative differenze tra gruppo di studio e gruppo           The Authors declare no conflict of interest.
di controllo per i guadagni medi del VOR dei canali semicircolari tranne che l’indice nor-
malizzato di asimmetria risultato più alto per i canali posteriori in fase acuta nel gruppo              How to cite this article: Califano L, Iannella
di studio. I guadagni medi del VOR dei canali posteriori affetti e controlaterali sani non               R, Mazzone S, et al. The Video Head Impulse
appaiono correlati con quelli dei canali anteriori ipsi e controlaterale al canale affetto.              Test in the acute stage of posterior canal benign
Conclusioni. Il vHIT non sembra strumento indispensabile in fase acuta di canalolitiasi                  paroxysmal positional vertigo. Acta Otorhi-
posteriore, almeno in una popolazione al primo episodio acuto. Risultati differenti potreb-              nolaryngol Ital 2021;41:69-76. https://doi.
bero essere riscontrati nelle forme recidivanti, resistenti alla terapia, di lunga durata o              org/10.14639/0392-100X-N1033
nelle varianti atipiche in cui la recidivanza, la lunga persistenza degli otoliti nel canale o
                                                                                                       © Società Italiana di Otorinolaringoiatria
un jam canalare potrebbero determinare danni maggiori.
                                                                                                       e Chirurgia Cervico-Facciale
PAROLE CHIAVE: BPPV, canalolitiasi posteriore, vHIT, riflesso vestibulo-oculomotore
                                                                                                                      OPEN ACCESS

                                                                                                       This is an open access article distributed in accordance with
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Introduction                                                                                           Commercial-NoDerivatives 4.0 International) license. The
                                                                                                       article can be used by giving appropriate credit and mentio-
                                                                                                       ning the license, but only for non-commercial purposes and
Benign paroxysmal positional vertigo (BPPV) is the most frequent acute ver-                            only in the original version. For further information: https://
tigo, accounting for up to 25% of observations in specialist clinics 1. The de-                        creativecommons.org/licenses/by-nc-nd/4.0/deed.en




                                                                                                                                                                 69
L. Califano et al.




tachment of otoconia and complex membranous fragments            were normal, before and after repositioning manoeuvres,
from the macula of the utriculum and their dislocation in        and there were no significant differences with the control
the semicircular canals (SC) are considered to be its most       population; only 2/24 patients presented a decreased VOR
likely pathogenesis. The posterior canal (PC) is involved in     gain of the affected PC. Karawani 12 found that in 3/3 cases
70-90% of cases, the lateral canal (LC) in 5-30% and the         of PC BPPV “vHIT showed injury of the posterior semi-
anterior canal (AC) in 1-5% 1. Otoconia may remain free-         circular canal”. Aslan 13 wrote that “20/30 patients who
floating in a canal (canalolithiasis), adhere to the cupula of   were diagnosed with vertical canal BPPV… had low VOR
a canal making it sensitive to gravity (cupulolithiasis), or     gains in the vertical canals”. In patients with isolated loss
entirely/partially plugging the canal lumen causing block-       of the PC function, Tarnutzer 14 reported 4 cases of PC BP-
age of the endolymphatic flow (canal jam).                       PV out of 52 patients with this rare condition. Castellucci 15
Halmagyi and Curthoys 2 introduced the head impulse test         described 3 patients with downbeat positional nystagmus
(HIT) in vestibular examination. In its clinical use, the        and selective deficit of the VOR gain of the affected PC.
presence of catch-up saccades after a high speed and small       Their finding supported the hypothesis of a partial cana-
amplitude movement of the head is observed by the na-            lith jam in the non-ampullary arm of the affected PC as the
ked eye immediately after the head impulse, with a specific      cause of the positional downbeat nystagmus.
field of application during acute unilateral vestibular defi-    An abstract has also been presented in which BPPV pa-
cit. Video head impulse test (vHIT) 3,4 is the instrumental      tients showed a higher VOR gain asymmetry of the vertical
evolution of HIT.                                                canals compared to healthy subjects 16.
vHIT allows clinicians to objectively measure the func-          All papers report few or very few cases: the largest series
tional activity of all SC considering both the vestibulo ocu-    were reported by Çınar 11, describing 24 cases of PC BP-
lar reflex (VOR) gain and the presence of overt or covert        PV, and by Aslan 13 reporting on 30 cases of vertical canal
saccades to verify whether or not canal function is com-         BPPV. Furthermore, the results of these two studies are not
promised. vHIT is performed through unpredictable high           in accordance.
speed and small amplitude head thrusts in the plane of each      The possible impairment of VOR gain of the vertical canals
co-planar pair of SC: horizontal plane for right and left LCs    has also been described in cerebellar lesions, but, in this
(L-L plane); LARP plane for Left Anterior and Right Pos-         case, other signs of central suffering are present 17. Lerchundi
terior canals; RALP plane for Right Anterior and Left Pos-       described a new syndrome in elderly patients termed “bilat-
terior canals. In LARP and RALP stimulations, the stimu-         eral posterior semicircular canal dysfunction”, usually idi-
lus is along vertical planes, forwards and downwards for         opathic, often associated with bilateral sensorineural hearing
AC, and backwards and upwards for PC 4.                          loss which could present positional downbeat nystagmus.
The literature reports that the study of LC allows evalua-       Chronic gait instability is the most common complaint 18.
tion of both VOR gain and possible presence of overt or          The possible age-related reduction of PC VOR gain has been
covert catch-up saccades, whereas for vertical canals clini-     previously described by Jimenez 19.
cians usually consider only the VOR gain, as the data on the     The aim of our study is to determine if vHIT is a useful
refixation saccades in LARP and RALP planes are not yet          diagnostic tool during the first acute episode of typical PC
well replicable 5.                                               BPPV, evaluating if an altered response of the ampullar re-
Few data on vHIT are reported in literature during the           ceptor is present in PC lithiasis.
acute stage of vertical canals BPPV. Mangabeira Alber-
naz 6 reported that in 12/14 cases of BPPV the canal gain
was normal, except for a patient with contralateral AC hy-
                                                                 Materials and methods
pofunction, whereas in another case the interpretation was       150 patients with the first diagnosed episode of unilateral
ambiguous due to the coexistence of previous otological          PC BPPV were included in the study between January and
disease. Perez-Fernandez 7 found a normal canal VOR in           December 2019 to evaluate the VOR gain of the affected
12 patients with AC BPPV. Fallahnezhad 8 reported a de-          canal through vHIT at three time points: a) during the early
creased gain of the affected PC in 16/29 cases of PC BPPV.       acute phase of the disease, prior to treatment with physical
Casani 9 described 2 cases of Lindsay-Hemenway syn-              manoeuvres; b) immediately after resolution of the acute
drome (PC BPPV arising after an acute unilateral vestibular      phase; and c) at one month.
deficit) 10, in which the gain of the PC, which is usually not   Inclusion criteria were: 1. Age > 18 years; 2. First episode
affected in the case of superior vestibular nerve deficit, was   of BPPV; 3. Diagnosis of unilateral PC BPPV; 4. Onset
decreased. Çınar 11 reported that in 24 patients with PC BP-     of symptoms within one week prior to the examination;
PV both the PC gain and the interaural PC gain asymmetry         5. Absence of any relationship between the onset of the



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                                                                                                             vHIT and posterior canal BPPV




acute positional vertigo and any trauma (also in the form of
an iatrogenic microtrauma, such as dental surgery); 6. Ab-
sence of previous acute vertiginous episodes; 7. Absence
of other otological/neurological pathologies (Meniere’s
disease, otosclerosis, VIII cranial nerve schwannoma, ves-
tibular neuritis, significant mono or bilateral hearing loss,
demyelinating and neurodegenerative diseases, other rarer
diseases); 8. Not migraineurs; 9. Absence of serious visual
problems; 10. Ability to complete vHIT in all the stimula-
tion planes.
The diagnosis of PC BPPV was based on the presence of
paroxysmal positional upbeat nystagmus with torsional
components beating towards the lowermost ear in ipsilat-
eral Dix-Hallpike positioning, with reversal when returning
to the sitting position 1.                                         Figure 1. Coplanar orientation of gaze and vertical canals plane during a
Immediately after diagnosis, in the sitting position, patients     LARP stimulation (from McGarvie et al. 20, mod.).
underwent vHIT for study of lateral and vertical semi-circu-
lar canals function through stimuli on L-L, LARP and RALP
planes, using a high-frame-rate (250 frames/sec,) video-           After vHIT, patients underwent the Quick Liberatory Ro-
oculography device (ICS Impulse®, Natus Medical) which             tation manoeuvre (QLR) 21. Patients were checked after 3,
tests only the right eye. The head mounted camera records          7 and 10 days until a negative Dix-Hallpike test was ob-
eye and head angular velocities: the ratio between the two         served. At this point, re-evaluation through vHIT was car-
values is the gain VOR for that stimulation. Twenty artifact-      ried out in all patients. Finally, patients were scheduled for
free impulses were considered for LC, and 10 for RALP and          a follow-up evaluation at one month after resolution.
LARP planes. The range of velocity for accepted impulses           Statistical analysis was performed with descriptive statis-
was set at 150-210°/sec for the lateral plane, at 110-150°/sec     tics and confidence intervals of a mean, unpaired T-test,
for the vertical planes. In testing LARP and RALP planes,          Pearson correlation test and Grubbs’ test to detect an out-
the horizontal gaze direction must be aligned with the ca-         lier, with significance level set at 0.05, 95% confidence in-
nal plane being tested, otherwise the measured vertical VOR        terval, using Graph pad Quick Calcs software. The statis-
gain decrease could mimic a canal deficit 20 (Fig. 1). Nor-        tical power analysis was calculated both through Satorra
mative values were obtained in a healthy population of 100         and Saris’s method - Structural Equation Model based on
individuals: 44 males, 56 females, considered as a control         the Chi-squared test 22 – (good statistical power if power
group. In the case of VOR gain significantly different from        value ≥ 0.80) and through MacCallum’s method- Structural
the control group (for posterior canal: 0.79 ± 2 SD = 0.55,        Equation Model based on Root-Mean-Square Error of Ap-
see below), the test was repeated three times, considering the     proximation (RMSEA) 23 – (good fitting of the proposed
highest measurement for the evaluation.                            model with RMSEA ≤ 0.8).
The mean VOR gain of the affected PC was compared with             All procedures were in accordance with the ethical stand-
data from the control group and from the contralateral healthy     ards of the Ethics Review Board and with the 1964 Hel-
PC. Normalised asymmetry ratio (NAR) between the gains of          sinki declaration and its later amendments.
the affected PC and of the contralateral healthy PC was calcu-
lated using the formula: NAR = (affected canal gain-healthy
                                                                   Results
canal gain)/(affected canal gain+healthy canal gain) x 100.
Consequently, its value is negative when the gain of the affect-   The control group consisted of 100 individuals, 56 females
ed canal is lower than the gain of the healthy canal, and posi-    and 44 males, with a F/M ratio of 1.27 and a mean age of
tive in the opposite case. A difference ≥ 15% was considered       58. ± 13.21 years (range 19-81 years, median 59.5 years).
significant. We also analysed the correlations between the PC
gain and both ipsilateral AC and contralateral AC gains; in the    vHIT assessment
first case the link could be the anatomical contiguity between     LC: mean VOR gain 0.99 ± 0,113; PC: mean VOR gain
the ipsilateral PC and AC, and in the second case a functional     0.79 ± 0.121; AC: mean VOR gain 0.73 ± 0.094. Differenc-
link could be identified through the push-pull stimulation in      es between the age classes were not significant, except for
LARP and RALP planes.                                              patients > 75 years. In this subgroup (8 patients), the mean



                                                                                                                                        71
L. Califano et al.




VOR gain of LC was 1.06 ± 0.051, which was significantly                         the affected PCs and the healthy contralateral canals was
higher than the mean VOR gain of LC in individuals < 75                          significant (p = 0.01) due to the mild mean VOR gain in-
years (0.98 ± 0,101, p = 0.028). In 5 of 200 PC, the gain                        crease of the non-affected PC and the mild mean VOR gain
was between 0.56 and 0.60. No outlier was detected. Mean                         decrease of the affected PC compared to the PC mean VOR
NAR between right and left PC was 3.8 ± 7.76. The maxi-                          gain of the control group. The mean NAR between affect-
mum NAR was 13.1% (absolute value). The correlations                             ed and healthy PC was -7.1 ± 9.65 (range from -38.6% to
between the mean VOR gain of PC and the mean VOR                                 +6.9%), which was significantly different from the control
gains of both the ipsilateral AC and the contralateral AC                        group (p = 0.004). The correlation between the mean VOR
were weak and not significant, for both ipsilateral PC and                       gains of AC and PC was weakly positive, but not significant:
AC (r = 0.1235; p = 0.10561), and for PC and contralateral                       for ipsilateral PC and AC, r = 0.178; p = 0.4; for LARP and
AC (r = 0.0987: p = 0.16754).                                                    RALP r = 0.24076, p = 0.1. In the study group, overt catch-
The study group consisted of 150 patients, 91 females                            up saccades in the affected PC plane were observed in six
and 59 males, with a F/M ratio of 1.54, and a mean age of                        patients with the lowest observed VOR gains (Fig. 2). The
60.6 ± 13.16 years (range 19-91 years, median 59 years).                         mean number of liberatory manoeuvres necessary to cure
The mean age was not significantly different from the con-                       PC BPPV was not significantly different between the sub-
trol group (p = 0.95). Statistical power for Structural Equa-                    group with either normal or not far from the normal VOR
tion Model based on Chi-squared test was 0.8, RMSEA                              gain- within 1 standard deviation (140 patients), and the
was 0.05.                                                                        subgroup of 10 patients with PC VOR gain ≤ 0.55, which
                                                                                 was far more than 2 standard deviations from the normal
vHIT: pre-treatment assessment                                                   value (mean: 2.04 ± 0.65 vs 2.06 ± 0, 74, p = 0.9).
The mean VOR gains were: 0.75 ± 0.152 for the affected                           Data of pre-treatment assessment from the control and
PC; 0.81 ± 0.113 for the healthy PC; 0.71 ± 0.098 for AC;                        study groups are reported in Table I.
0.98 ± 0.124 for LC. In 10/150 patients (6.7%) the VOR
gain of the affected PC was ≤ 0.55 (range 0.36-0.50), i.e.                       vHIT: post-treatment assessment
two standard deviations less than the mean PC VOR gain                           The mean VOR gains were 0.77 ± 0.127 for treated
of the control group; in two of these patients (both were                        PC; 0.81 ± 0.161 for healthy PC; 0.73 ± 0.144 for AC;
> 70 years) the healthy contralateral PC VOR gain was also                       0.98 ± 0.212 for LC. In 9/10 cases with pre-treatment VOR
≤ 0.55. Only one case among the VOR gains of the affected                        gain of the affected PC ≤ 0.55, VOR gain improved but
PC was considered as furthest from the other values, but                         did not reach a normal level (new range: 0.57-0.64); in the
was not a significant outlier. Mean VOR gain differences                         lattest case the post-treatment gain was normal (0.74, pre-
between both the affected PC and the contralateral healthy                       treatment value: 0.36). The mean VOR gain difference be-
PC vs the control group were not significant (respectively,                      tween pre-treatment and post-treatment values of the affect-
p = 0.33; p = 0.18). The mean VOR gain difference between                        ed PC was not significant (0.77 vs 0.75, p = 0.5), whereas




Figure 2. vHIT: a case of low VOR gain in an acute left posterior canal BPPV with overt scattered catch-up saccades.



72
                                                                                                                                                  vHIT and posterior canal BPPV




Table I. vHIT assessment in the control and study groups (pre-treatment assessment).
                                    Lateral canal mean VOR         Affected posterior canal                        Healthy posterior canal                 Anterior canal
                                               gain                     mean VOR gain                                 mean VOR gain                        mean VOR gain
 Control group                                    0.99 ± 0.113                             -                             0.79 ± 0.121                        0.73 ± 0.094
 Study group                                      0.98 ± 0.124                       0.75 ± 0.152*                       0.81 ± 0.113*                       0.71 ± 0.098
*Significant difference in the study group between VOR gains of affected vs. healthy posterior canals (* p = 0.01). Differences between VOR gains of all semi-circular canals in the
control vs. study groups are not significant.



the difference with the mean VOR gain of contralateral non-                                   lying pathophysiologic mechanism. Otoconia can be either
affected PC remained significant (0.77 vs. 0.81, p = 0.04).                                   free-floating in a semicircular canal or adherent to a semi-
No outlier was detected. The mean NAR between affected                                        circular canal cupula; rarely they can provoke a “canal
and healthy PC was -5.4 ± 7.0, which was not significantly                                    jam”. Since 2001 the possible role of the canal jam in some
different from the pre-treatment value (p = 0.156) and not                                    forms of canalolithiasis has been reported 24. Later, other
significant compared to the control group (p = 0.09).                                         authors reported the same mechanism in rare cases of posi-
In both the pre-treatment and post-treatment assessments,                                     tional vertigo. Luis 25 reported a case of direction-fixed nys-
no significant difference was observed between the gains                                      tagmus lateral canal BPPV characterised by a deficiency of
of AC and LC in the control and study, and in the VOR                                         the cupular-endolymph high-frequency system dynamics
gain differences for age classes for vertical canals, whereas                                 due to the presence of a block of the endolymphatic flow in
the difference was not significant for LC in the subgroup                                     the affected canal. The deficiency was resolved after suc-
> 75 years (15 patients), in which the mean VOR gain was                                      cess of the liberatory manoeuvre. Castellucci 26 described
higher (p = 0.07).                                                                            an analogous case with isolated lateral canal hypofunction,
                                                                                              ascribed to a canal jam, that was resolved by repeated head
One-month assessment                                                                          shaking and conversion into a typical geotropic LC BPPV.
82 patients attended the scheduled examination. All were                                      Schubert 27 considered that in some cases of direction-fixed
disease-free at Dix-Hallpike test; three reported mild resid-                                 nystagmus LC BPPV, the otoconial jam acts as a “false”
ual dizziness. The mean VOR gains were 0.78 ± 0.215 for                                       cupula, which causes a modification in velocity but not in
the treated PC; 0.80 ± 0.248 for the healthy PC; 0.73 ± 0.199                                 the direction of the nystagmus that depends on head posi-
for AC; 0.98 ± 0.178 for LC. In 3 cases with pre-treatment                                    tion. As already mentioned, Castellucci 15 described also
VOR gain of the affected PC ≤ 0.55, VOR gain was nor-                                         some cases regarding the vertical canals. In these cases,
mal (new range: 0.71-0.77). No outlier was detected. The                                      the authors’ interpretation was that a canal jam in the non-
difference between the mean VOR gains of affected and                                         ampullary tract of the PC caused a partial block of the en-
healthy PC was no longer significant (p = 0.58). The mean                                     dolymphatic flow. Acting as a ”low-pass filter”, the jam al-
NAR between treated and healthy PC was -4.9 ± 8.4, not                                        lowed cupular activation by otoconia movements but not
significantly different from the control group (p = 0.36) and                                 a good cupular response to high frequency impulses, as in
from the pre-treatment value (p = 0.11). Data of PC VOR                                       vHIT. Obviously, this mechanism may be applied both to
gain in the study group are summarised in Table II.                                           LC BPPV and to PC BPPV. Thus, the canal jam would act
                                                                                              by modifying the endolymphatic dynamics of the affected
                                                                                              canal.
Discussion                                                                                    Except in the specific case of a presumed canal jam, which
BPPV is the most frequent acute vertigo and detachment of                                     is theoretically conceivable in only a small minority of
otoconia from the utricular macula is considered the under-                                   cases, pathogenetic hypotheses involving mechanic factors


Table II. vHIT assessment of the posterior canal in the study group.
                                                                  Affected posterior canal                                               Healthy posterior canal
                                                                      Mean VOR gain                                                         Mean VOR gain
 Pre-treatment                                                                    0.75 ± 0.152*                                               0.81 ± 0.113*
 Post-treatment                                                                   0.77 ± 0.127**                                              0.81 ± 0.161**
 One-month evaluation                                                             0.78 ± 0.215***                                             0.80 ± 0.248***
Significant differences in the study group between VOR gains of affected vs. healthy posterior canals in pretreatment evaluation and immediate post-treatment evaluation
(* p = 0.01; ** p = 0.04). Not significant difference at the one-month evaluation (*** p = 0.58).




                                                                                                                                                                                   73
L. Califano et al.




give no immediate answer about a possible VOR gain im-           the PC cupular receptor to provoke specific oculomotor
pairment of the affected canal.                                  reflex responses through the activation of the contralateral
Caloric and rotatory techniques have been used to approach       superior rectus and ipsilateral inferior obliquus muscles, re-
the problem. A transient caloric hypofunction was pointed        sponsible for the fast phase vectors.
out in the case of LC BPPV 28. A strong cold-water caloric       Does damage to the PC ampulla actually exist or should
stimulus (24°C) had a significant inhibitory effect on the       abnormal responses be considered as a result of an anoma-
ipsilateral horizontal high-acceleration VOR-gain, assessed      lous stimulus acting on a normal receptor? In other words,
with vHIT, emphasising the importance of the non-linear          are we discussing of a purely mechanical disorder of the
pathway when vestibular organs are probed with high-             inner ear or does the mechanical disorder provoke either
acceleration stimuli 29. These data were also confirmed          deficient or irritative responses of the ampullar receptor?
through cold stimulation in the prone position, which has        We analysed 150 patients exhibiting the first episode of
physiologic excitatory effects on LC cupula. This might oc-      typical PC-BPPV. Mean VOR gains of all semi-circular ca-
cur because the cupular deviation in either direction elicits    nals were not significantly different between the study and
a partial mechanical and electrophysiological saturation,        control. In particular, in the pre-treatment phase, the mean
decreasing cupular sensitivity with respect to high accel-       VOR gain of the affected PC was not significantly different
eration stimuli 30. In 6 patients with PC BPPV, the pendular     compared to the control group (p = 0.33), but significantly
rotation test in a head-tilted position gave a lower response    lower than the mean VOR gain of the healthy contralateral
of PC respect to AC 31. In patients with BPPV, during a si-      PC (p = 0.01); this significant difference was also main-
nusoidal rotation VOR gains of the vertical canals were not      tained in the post-treatment phase (p = 0.04), despite a mild
changed in comparison with normal subjects 32.                   increment in the mean VOR gain of the affected PC, which
Since 2013, the availability to test all six semi-circular ca-   was not significant with respect to the pre-treatment assess-
nals through vHIT has allowed clinicians to evaluate the         ment (p = 0.5). At the one-month evaluation, the difference
VOR gain for each of them, using specific planar stimuli:        between the mean VOR gains of affected and healthy PC
L-L plane for LC, LARP plane for Left AC and Right PC,           was no longer significant (p = 0.58).
RALP plane for Right AC and Left PC 4. At present, vHIT          According to our results, PC VOR gain does not seem to
is probably the most effective tool to evaluate the semi-cir-    be significantly affected in patients with typical PC BPPV,
cular canals function.                                           but in a small subgroup of 10 patients (6.7%) with a dif-
The high incidence of PC BPPV opened a window to study           ferent behaviour it does exist. In these cases, the PC VOR
PC function during the acute stage of the disease with vHIT.     gain was ≤ 0.55, our cut-off value for a clearly impaired
So far, few papers have been published on this topic. As         PC function, within a range of 0.36-0.50, and, interestingly,
mentioned, a limited number of cases have been reported,         after the resolution of the acute phase, it improved in all
with contrasting results about the functional impairment of      patients. It appears likely that in these cases the VOR gain
PC activity. Fallahnezhad 8, Karawani 12 and Aslan 13 re-        deficit was directly due to the canalolithiasis effects on the
ported a significant lowering of PC VOR gain during the          ampullar receptor stimulation. In 2 patients > 70 years with
acute stage of PC BPPV. Data from Casani 9 in two cases of       bilateral PC VOR gain < 0.55, a possible age related reduc-
Lindsay-Hemenway syndrome are not easily understand-             tion of PC VOR gain 19 was considered possible, but the
able: the reported posterior canal VOR gain deficit could        successive normalisation of the values during the follow-up
be due either to the previous acute vestibular neuritis as in    excluded this diagnosis.
our opinion as the Authors meant or it could be due to a         The correlation of the mean VOR gain of AC with the mean
secondary canalolithiasis. It is also worth mentioning the       VOR gain of the affected PC was weakly positive but not
data reported by Castellucci et al. 15 about a rare variant,     significant, as also seen in the control group. This means
apogeotropic PC BPPV, in which, at least in some cases, a        that both the ipsilateral AC in a possible anatomical con-
PC incomplete jam could be hypothesised. In their cases,         tiguity relationship and the contralateral AC in a possible
vHIT was also a useful tool to discriminate between the          functional relationship during LARP and RALP push-pull
involvement of either the PC or the contralateral AC.            stimulations seem to be functionally unaffected by the hy-
In typical PC BPPV, the mechanism provoking the parox-           drodynamic changes induced by PC canalolithiasis.
ysmal nystagmus is considered to be ampullophugal endo-          Our data suggest that in the acute phase of PC BPPV there
lymphatic flow in the affected PC induced by the free float-     is usually no alteration in the canal receptor response as
ing otoconia movement away from the cupula towards the           shown by the normality of the affected PC mean VOR gain,
most inferior portion of the canal during Dix-Hallpike test.     as in the control group. Paroxysmal positioning nystagmus,
According to Ewald’s II law, ampullophugal flow excites          which is the primary sign of the disease, has to be inter-



74
                                                                                                                vHIT and posterior canal BPPV




preted as being due to a normal receptor response to an ab-       mance in acute PC BPPV does not appear to be clinically
normal stimulus, and not to receptor dysfunction in terms         essential, recalling, however, the selected population of our
of either canalar hyporeflexia or hyperreflexia.                  study and the current limit that there are still very limited
However, a minority of cases (6.7%) in which the PC VOR           data in the literature regarding vHIT results in frequently
gain was significantly reduced, it does exist, with a trend       recurrent forms, in long-term forms, in non-responsive
in recovery immediately after resolution of the disease           forms, in atypical variants, which are specific issues in
through a liberatory manoeuvre. These cases did not show          which this test could have relevance. In these cases, hy-
any difference in the quantitative and qualitative features       pothetically, otoconia could be either partially entrapped
of the diagnostic paroxysmal positioning nystagmus, as            or embedded in some narrow portion of the affected canal
evidence of the preserved ability of the receptor to respond      causing their anomalous evolution. Interesting and perhaps
to the stimulus caused by the otoconial movement in the           different data could be obtained in forms we could label as
canal. It is therefore likely that in these cases the reduced     “cupulolithiasis” in which the PC receptor could be more
response may be related to the presence of otoconia in the        directly affected. The scientific method is based on hypoth-
canal determining in a sitting position a reduction of the        eses and their demonstration: all hypotheses need objective
stimulus provided during vHIT. In fact, at post-treatment         data to be supported. Ad hoc studies in those subgroups
assessment an improvement of the affected PC VOR gain             are thus required. Nonetheless, even in typical PC BPPV,
was observed in all cases, and in one case even its normali-      the information provided by vHIT is definitely useful for a
sation, whereas at the one-month visit all PC VOR gains           more complete assessment of the vertiginous patient.
were normal.
The significant difference between the mean VOR gains             References
of the affected PC and the contralateral PC, in both pre-         1
                                                                       Von Brevern M, Bertholon P, Brandt T, et al. Benign paroxysmal posi-
treatment and immediate post-treatment assessments, is not             tional vertigo: diagnostic criteria. Consensus document of the Commit-
easily justifiable. The pair of PC does not respond to the             tee for the Classification of Vestibular Disorders of the Bárány Society.
                                                                       J Vestib Res 2015;25;105-17. https://doi.org/10.3233/VES-150553
same push-pull stimulus, so that a decrease of the inhibi-        2
                                                                       Halmagyi GM, Curthoys IS. A clinical sign of canal pare-
tory stimulus of a weaker affected canal cannot be hypoth-             sis. Arch Neurol 1988;45:737-9. https://doi.org/10.1001/arch-
esised when it is in a “pull” situation during vHIT, as well           neur.1988.00520310043015
as the responses of the AC of the affected side, which is the     3
                                                                       MacDougall HG, Weber KP, McGarvie LA, et al. The video head im-
canal functionally related with the contralateral PC during            pulse test diagnostic accuracy in peripheral vestibulopathy. Neurology
                                                                       2009;73:1134-41. https://doi.org/10.1212/WNL.0b013e3181bacf85
LARP and RALP planes stimulations, were normal. Again,            4
                                                                       MacDougall HG, McGarvie LA, Halmagyi GM, et al. Application
the data cannot be justified by the decrease of the inhibitory         of the video head impulse test to detect vertical semicircular canal
quota on the global response in either the LARP or in the              dysfunction. Otol Neurotol 2013;34:974-9. https://doi.org/10.1097/
RALP planes provided by a normal contralateral AC when                 MAO.0b013e31828d676d
PC is stimulated. However, even if in a numerically smaller       5
                                                                       Singh NK, Govindaswamy R, Jagadish NV. Test-retest reliabil-
                                                                       ity of video head impulse test in healthy individuals and individu-
population, the difference between affected and healthy                als with dizziness. J Am Acad Audiol 2019;30:744-52. https://doi.
PCs was no longer significant at the one-month control.                org/10.3766/jaaa.17080
It should also be noted that our series relates to people suf-    6
                                                                       Mangabeira Albernaz PL, Zuma E Maia FC. The video head impulse
fering for the first time from acute BPPV. It cannot be ex-            test. Acta Otolaryngol 2014;134:1245-50. https://doi.org/10.3109/00
                                                                       016489.2014.942439
cluded that in a differently selected population, i.e. subjects   7
                                                                       Perez-Fernandez N, Martinez-Lopez M, Manrique-Huarte R. Ves-
with multiple recurrence of the disease, the situation of the          tibulo-ocular reflex in patients with superior semicircular canal be-
canal receptor may be different. We believe that future clin-          nign paroxysmal positional vertigo (BPPV). Acta Oto-Laryngologica
ical series should take this potential diversity into account.         2014;134:485-90. https://doi.org/10.3109/00016489.2013.871750.
                                                                  8
                                                                       Fallahnezhad T, Ghahraman MA, Farahani S, et al. Vestibulo-ocu-
                                                                       lar reflex abnormalities in posterior semicircular canal benign par-
Conclusions                                                            oxysmal positional vertigo: a pilot study. Iran J Otorhinolaryngol
                                                                       2017;29:269-74.
vHIT appears to play an ancillary role in the clinical man-       9
                                                                       Casani AP, Cerchiai N, Navari E. Paroxysmal positional vertigo de-
agement of patients suffering from acute PC BPPV. How-                 spite complete vestibular impairment: the role of instrumental as-
ever, vHIT can provide useful data for better understanding            sessment. Acta Otorhinolaryngol Ital 2018;38:563-8. https://doi.
                                                                       org/10.14639/0392-100X-1549
of the pathology, identify possible otological comorbidi-         10
                                                                       Hemenway W, Lindsay J. Postural vertigo due to unilateral sud-
ties, help to identify the affected canal, and can have foren-         den partial loss of vestibular function. Ann Otol Rhinol Laryngol
sic value in highlighting possible persistent canal damage.            1956;65:692-706. https://doi.org/10.1177/000348945606500311
Keeping in mind these considerations, its routine perfor-         11
                                                                       Çınar Y, Bayram A, Culfa R, et al. Analyses with the video head




                                                                                                                                            75
L. Califano et al.




     impulse test during the canalith repositioning maneuver in patients             “Quick Liberatory Rotation Manoeuvre”. Acta Otorhinolaryngol Ital
     with isolated posterior semicircular canal benign paroxysmal posi-              2003;23:161-7.
     tional vertigo. Turk Arch Otorhinolaryngol 2018;56:81-4. https://doi.      22
                                                                                     Satorra A, Saris WE. Power of the likelihood ratio test in covari-
     org/10.5152/tao.2018.3166                                                       ance structure analysis. Psychometrika 1985;50:83-90. https://doi.
12
     Karawani K, Bielińska M, Nowosielska-Grygiel J, et al. Compara-                 org/10.1007/BF02294150
     tive evaluation of the diagnostic value of the VHIT and Dix-Hallpike       23
                                                                                     MacCallum RC, Browne MW, Sugawara HM. Power analysis and de-
     test in patients with balance system disorders in out-patient healthcare        termination of sample size for covariance structure modeling. Psychol
     practice and expertise preparation. Otolaryngol Pol 2018;72:36-42.              Methods 1996;1:130-49. https://doi.org/10.1037/1082-989X.1.2.130
     https://doi.org/10.5604/01.3001.0012.5421                                  24
                                                                                     von Brevern M, Clarke AH, Lempert T. Continuous vertigo and spon-
13
     Aslan H, Pınar E, Aladağ İ, et al. Our results of VHIT on BPPV. Eur J           taneous nystagmus due to canalolithiasis of the horizontal canal. Neu-
     Rhinol Allergy 2018;1:12-4. https://doi.org/10.5152/ejra.2018.56708             rology 2001;56:684-6. https://doi.org/10.1212/wnl.56.5.684
14
     Tarnutzer AA, Bockisch CJ, Buffone E, et al. Association of posterior      25
                                                                                     Luis L, Costa J, Vaz Garcia F, et al. Spontaneous plugging of the
     semicircular canal hypofunction on video-head-impulse testing with              horizontal semicircular canal with reversible canal dysfunction and
     other vestibulo-cochlear deficits. Clin Neurophysiol 2017;128:1532-             recovery of vestibular evoked myogenic potentials. Otol Neurotol
     41. https://doi.org/10.1016/j.clinph.2017.04.029                                2013;34:743-7. https://doi.org/10.1097/MAO.0b013e318287f343
15
     Castellucci A, Malara P, Delmonte S, et al. A possible role of vid-        26
                                                                                     Castellucci A, Malara P, Brandolini C, et al. Isolated horizontal ca-
     eo-head impulse test in detecting canal involvement in benign par-              nal hypofunction differentiating a canalith jam from an acute periph-
     oxysmal positional vertigo presenting with positional downbeat                  eral vestibular loss. Am J Otolaryngol 2019;40:319-22. https://doi.
     nystagmus. Otol Neurotol 2020;41:386-91. https://doi.org/10.1097/               org/10.1016/j.amjoto.2018.12.005
     MAO.0000000000002500                                                       27
                                                                                     Schubert MC, Helminski J, Zee DS, et al. Horizontal semicircular
16
     Guan Q, Zhang L, Hong W, et al. Video head impulse test for evalu-              canal jam: two new cases and possible mechanisms. Laryngoscope
     ation of vestibular function in patients with vestibular neuritis and           Investig Otolaryngol 2020;5:163-7. https://doi.org/10.1002/lio2.352
     benign paroxysmal positional vertigo. J Zhejiang Univ (Med Sci)            28
                                                                                     Domènech Campos E, Armengol Canceller M, Barona de Guzman
     2017;46:52-8.                                                                   R. Vértigo posicional paroxístico benigno del canal horizontal. Acta
17
     Choi J-Y, Kim H-J, Kim J-S. Recent advances in head impulse test                Otorinolaringol Esp 2006;57:446-9. https://doi.org/10.1016/s0001-
     findings in central vestibular disorders. Neurology 2018;90:602-12.             6519(06)78746-5
     https://doi.org/10.1212/WNL.0000000000005206                               29
                                                                                     Tamás LT, Weber KP, Bockisch CJ, et al. Cold thermal irrigation de-
18
     Lerchundi F, Laffue AH, Olivier M, et al. Bilateral posterior semi-             creases the ipsilateral gain of the vestibulo-ocular reflex. Ear Hear
     circular canal dysfunction: a new finding with video head impulse               2017;38:e193-e9. https://doi.org/10.1097/AUD.0000000000000398
     test. J Neurol 2020;267:2347-52. https://doi.org/10.1007/s00415-           30
                                                                                     Tamás LT, Obrist D, Avan P, et al. Biasing the semicircular canal cu-
     020-09793-5                                                                     pula in excitatory direction decreases the gain of the vestibuloocu-
19
     Jiménez GG, Pérez Fernandez N. Reducción de la ganancia del ca-                 lar reflex for head impulses. J Vestib Res 2019;29:281-6. https://doi.
     nal semicircular posterior en el test del impulso cefálico con la edad.         org/10.3233/VES-190681
     Estudio observacional. Acta Otorrinolaringol Esp 2016;67:15-22.            31
                                                                                     IIda M, Igarashi M, Naitoh A, et al. Evaluation of the vertical canal
     https://doi.org/10.1016/j.otorri.2014.12.002                                    function by the pendular rotation test: a study on patients with be-
20
     McGarvie LA, Martinez-Lopez M, Burgess AM, et al. Horizon-                      nign paroxysmal positional vertigo. ORL J Otorhinolaryngol Suppl
     tal eye position affects measured vertical VOR gain on the video                1997;59:269-71. https://doi.org/10.1159/000276951
     head impulse test. Front Neurol 2015;6:58. https://doi.org/10.3389/        32
                                                                                     Sekine K, Imai T, Morita M, et al. Vertical canal function in
     fneur.2015.00058                                                                normal subjects and patients with benign paroxysmal posi-
21
     Califano L, Capparuccia PGG, Di Maria D, et al. Treatment of be-                tional vertigo. Acta Otolaryngol 2004;124:1046-52. https://doi.
     nign paroxysmal positional vertigo of posterior semicircular canal by           org/10.1080/00016480410018061




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