Vestibular migraine and benign paroxysmal positional vertigo,close presentation dilemma

Abstract

Background: Not only an association between benign paroxysmal positional vertigo (BPPV) and migraine have been recognized in the literature, but also, there are close similarities between BPPV and vestibular migraine (VM) presentations as both can be presented by very similar positional nystagmus.

Aims/objectives: To prescribe relatively uncommon cases of positional nystagmus caused by VM that mimics positioning nystagmus of BPPV.

Material and method: 12 patients were reviewed retrospectively in this study. All were subjected to full history taking, videonystagmography testing (VNG) and brain magnetic resonance imaging (MRI) with contrast. Provisionally, they were diagnosed with BPPV. After three attempts of repositioning sessions none of them improved. After exclusion of central insults using brain MRI, trial of anti-migraine medical treatment (50-100 Topiramate tablets once per day) for at least one month was prescribed to them.

Results: 10 patients were completely cured on medical treatment and finally were diagnosed VM. Only 2 patients did not improve on medical treatment (for one month), were managed again by repeated repositioning maneuvers till finally improved and were diagnosed as resistant BPPV.

Conclusions/significance: VM positional nystagmus can mimic BPPV nystagmus in some patients.     

Differentiation of migrainous positional vertigo (MPV) from horizontal canal benign paroxysmal positional vertigo (HC-BPPV)

This article presents an approach to differentiation of migrainous positional vertigo (MPV) from horizontal canal benign paroxysmal positional vertigo (HC-BPPV). Such an approach is essential because of the difference in intervention between the two disorders in question. Results from evaluation of the case study presented here revealed a persistent ageotropic positional nystagmus consistent with MPV or a cupulolithiasis variant of HC-BPPV. The patient was treated with liberatory maneuvers to remove possible otoconial debris from the horizontal canal in an attempt, in turn, to provide further diagnostic information. There was no change in symptoms following treatment for HC-BPPV. This case was diagnosed subsequently as MPV, and the patient was referred for medical intervention. Treatment has been successful for 22 months. Incorporation of HC-BPPV treatment, therefore, may provide useful information in the differential diagnosis of MPV and the cupulolithiasis variant of HC-BPPV.     

Clinical characteristics of patients with multi-canal benign paroxysmal positional vertigo

IntroductionMulti-canal benign paroxysmal positional vertigo is considered to be a rare and controversial type in the new diagnostic guidelines of Bárány because the nystagmus is more complicated or atypical, which is worthy of further study.ObjectiveBased on the diagnostic criteria for multi-canal benign paroxysmal positional vertigo proposed by International Bárány Society, the study aimed to investigate the clinical characteristics, diagnosis and treatment of multi-canal benign paroxysmal positional vertigo.MethodsA total of 41 patients with multi-canal benign paroxysmal positional vertigo were included and diagnosed by Roll, Dix-Hallpike and straight head hanging tests. Manual reduction was performed according to the involvement of semicircular canals.ResultsAmong the 41 cases, 19 (46.3%) patients showed vertical up-beating nystagmus with or without torsional component and geotropic, apogeotropic horizontal nystagmus, and were diagnosed with posterior-horizontal canal. 11 (26.8%) patients showed vertical up-beating nystagmus with torsional component on one side and vertical down-beating nystagmus with or without torsional component on the other side during Dix-Hallpike test or straight head hanging test and were diagnosed with posterior-anterior canal benign paroxysmal positional vertigo 9 (26.8%) patients showed vertical down-beating nystagmus with or without torsional component and geotropic, apogeotropic horizontal nystagmus, and were diagnosed with anterior-horizontal canal 2 (4.9%) patients showed vertical geotropic torsional up-beating nystagmus on both sides and were diagnosed with bilateral posterior canal benign paroxysmal positional vertigo. High correlation between the sides with reduced vestibular function or hearing loss and the side affected by Multi-canal benign paroxysmal positional vertigo was revealed (contingency coefficient = 0.602, p = 0.010). During one-week follow up, nystagmus/vertigo has been significantly alleviated or disappeared in 87.8% (36/41) patients.ConclusionPosterior-horizontal canal benign paroxysmal positional vertigo was the most common type. Multi-canal benign paroxysmal positional vertigo involving anterior canal was also not uncommon. Caloric tests and pure tone audiometry may help in the determination of the affected side. Manual reduction was effective in most of Multi-canal benign paroxysmal positional vertigo patients.     

Postural stability in patients with different durations of benign paroxysmal positional vertigo

Postural stability maintenance was investigated in patients with idiopathic benign paroxysmal positional vertigo of the posterior semicircular canal (BPPV-PSC) and compared to healthy subjects. To measure the postural stability during a quiet upright stance, we used static posturography in two conditions: with open and with closed eyes. The effect of the repositioning Epleys maneuver on the recovery of postural stability in patients with different durations of BPPV-PSC less than 60 days after the first attack of positioning vertigo (group I) and more than 60 days (group II) was examined. The investigation was made 1 h after the positive Dix-Hallpike test and 7 days after treatment with the Epley maneuver. Sway velocity (SV) and relative power spectrum (RPS) of the stabilograms were calculated to evaluate the postural stability for each subject and each experimental condition. We found a pronounced spectral density peak in the frequency range of 1.0–2.0 Hz and smaller spectral density in the range of 0.15–0.5 Hz compared to that in healthy subjects. Our results showed that the postural maintenance in BPPV-PSC patients depended on the disease duration. Patients with a duration of BPPV symptoms less than 60 days after the first attack demonstrated a high dependence on the visual input for postural stability. One week after the Epley maneuver, differences in the recovery of postural control in both groups of patients were also found. We assume that the disturbed otolith function together with the impaired dynamics of the semicircular canal generate a particular pattern of postural maintenance. The different degree of restoration of postural stability 1 week after the EM treatment in BPPV-PSC patients with different durations of the disease gives us reason to believe that after removing the otoconia from the semicircular canal, some stimulation of other sensory subsystems and adaptation mechanisms occur that lead to a new pattern of postural maintenance.     

Variables affecting treatment in benign paroxysmal positional vertigo

OBJECTIVE: To identify variables affecting outcome in patients with benign paroxysmal positional vertigo (BPPV) treated with canalith repositioning maneuvers. STUDY DESIGN: Retrospective review of patients at a tertiary vestibular rehabilitation center. METHODS: Variables identified for statistical analysis included method of diagnosis, age, sex, onset association with trauma, semicircular canal involvement, presence of bilateral disease, treatment visits, and cycles of canalith repositioning maneuvers per treatment visit. Multivariate statistical analysis using Pearson chi2, likelihood ratio, linear-by-linear association, and cross-tabulation tests were performed. RESULTS: Two hundred fifty-nine patients with BPPV who received treatment were identified from 1996 to 1998. Average follow-up time was 16.9 months. 74.8% required one treatment visit, 19.0% required a second treatment visit, and 98.4% were successfully treated after three treatment visits. The remainder required up to seven treatment visits for relief of symptoms. Variables affecting the number of treatment visits included bilateral disease or location of disease other than in the posterior semicircular canal. Patient age, sex, method of diagnosis, and onset association with trauma had no statistically significant impact. CONCLUSION: Patients with benign paroxysmal positional vertigo not located in a single posterior semicircular canal are more likely to require multiple visits for canalith repositioning.     

Idiopathic benign paroxysmal positional vertigo with persistent vertigo/dizziness sensation is associated with latent canal paresis,endolymphatic hydrops,and osteoporosis

Objective

The aim of the present study was to examine the association of neuro-otological examination, blood test, and scoring questionnaire data with treatment-resistant intractability in idiopathic benign paroxysmal positional vertigo (BPPV) patients.

Subjective visual vertical in patients with benign paroxysmal positional vertigo.

The ocular tilt reaction leads to an alteration in the subjective visual vertical (SVV). Nonsurgical peripheral vestibular dysfunction only rarely leads to changes in the SVV. To our knowledge, no studies have examined the effects on the SVV in patients with benign positional paroxysmal vertigo (BPPV) post Hallpike and Semont maneuvers. Sixteen patients with posterior canal BPPV were assessed in the vestibular clinic in Winnipeg, Manitoba. These patients had assessment of their SVV at baseline, post Hallpike and Semont maneuvers, and at follow-up 2 weeks later. These patients were also compared to a control group (n = 9). Ten of 16 patients showed a statistically significant change in SVV post Hallpike maneuver. An even larger number of patients, 14 of 16, showed a significant difference when compared to the control group post Hallpike. These findings suggest that the inferior vestibular nerve may to some degree influence the ocular tilt reaction.     

Postural control in horizontal benign paroxysmal positional vertigo

Sixteen patients affected by benign paroxysmal positional vertigo of the horizontal semicircular canal (BPPV-HSC) were investigated by means of dynamic posturography (DP) and during bithermal caloric stimulation. Data were compared to data from 40 patients with benign paroxysmal positional vertigo of the posterior semicircular canal (BPPV-PSC) and 20 healthy controls. No postural deficit was observed before or after a liberative Lempert’s manoeuvre when patients were compared to control subjects. BPPV-PSC postural scores were significantly impaired compared to scores from the BPPV-HSC group. A residual significant postural impairment was also observed after a successful liberative manoeuvre in the BPPV-PSC group. Electronystagmographic recordings before recovery revealed significant hypoexcitability of the affected ear in 8/16 patients of the BPPV-HSC group. After the liberative manoeuvre, a symmetric bilateral response to caloric stimulation was recorded in all patients. Three main conclusions can be drawn from the present data. First, disorders of the horizontal semicircular canal do not change postural control. Second, dynamic posturography can detect the postural imbalance due to posterior semicircular canal dysfunction even after resolution of paroxysmal vertigo attacks. Third, utricular dysfunction can be ruled out as a cause of the residual postural deficit observed in BPPV-PSC patients. Therefore the recovery delay observed even 1 month after the liberative manoeuvre in the BPPV-PSC-group might be due to the persistence of small amounts of residual debris in the canal, to paralysis of ampullar receptors, or to the time needed for central vestibular re-adaptation. Received: 2 December 1999 / Accepted: 17 February 2000     

Seasonality and solar radiation variation level in benign paroxysmal positional vertigo

Background: Several studies have shown that the incidence of benign paroxysmal positional vertigo (BPPV) presents seasonal variations and there is evidence that the variation in time is dependent on the patient’s amount of vitamin D.

Objectives: This is a retrospective study to verify if there is a correlation between the incidence of BPPV and the level of solar radiation, essential for the synthesis of vitamin D in the skin.

Material and methods: This study comprised 214 patients with BPPV seen from 2012 to 2017, in a city Latitude: ?30.0277, Longitude: ?51.2287 30° 1′ 40″ South, 51° 13′ 43″ West. The amounts of monthly solar radiation were analyzed in relation to the dates of their first consultations. Statistical tests were employed to verify the existence of a correlation between solar radiation and the incidence of the disease.

Results: The statistical analysis revealed a significant difference between the incidence of BPPV and the amount of radiation during the month of the diagnosis of the disease. There was also a significant statistical correlation with the climatic variation.

Conclusion: More patients with benign paroxysmal positional vertigo (BPPV) are seen in consultation in the months with low solar radiation and in the autumn and winter seasons, in this geographic city.     

Long-term outcome and health-related quality of life in benign paroxysmal positional vertigo

A prospective cohort study was designed to evaluate the long-term outcome and health-related quality of life (HRQoL) in patients with posterior canal benign paroxysmal positional vertigo (PC-BPPV) treated by the particle repositioning maneuver (PRM) in the outpatient clinic of a general community hospital. Fifty individuals with PC-BPPV were included, and 45 (90%) completed the study. The diagnosis was based on the history of short episodes of vertigo and a positional nystagmus during the Dix-Hallpike test (DHT). All patients were treated by a single PRM, and relapses were evaluated by DHT at 30, 180 and 360 days post-treatment; a new PRM was performed if the DHT was positive. The main outcome measures were: percentage of patients with a negative DHT after treatment, scores obtained on the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) and the Dizziness Handicap Inventory Short Form (DHI-S) before and 30, 180 and 360 days post-treatment. The DHT was found negative in 80% (40/50) of individuals at 30 days. Ten, seven and five patients presented a positive DHT at 30, 180 and 360 days, respectively. Persistent BPPV was observed in 5% (2/50) of patients at 360 days, despite repeated PRM. Relapses (DH+ after successful PRM) were observed in 7.5% (3/50) at 180 days and 360 days. Both questionnaires showed a reliability Cronbachs alpha >0.7. The average standardized score for each SF-36 scale was compared with the reference population normative data, showing differences with norms for all scales except for vitality. After PRM, patients improved their scores with both instruments, indicating a restoration of HRQoL at 30 days. Physical dimension scores of the SF-36 improved from day 30 to 360. DHI-S scores were statistically better after PRM (P<0.001). Our results show that the effectiveness of PRM is 88% after 1 year of follow-up. Patients with BPPV experienced a decrease in HRQoL, which was restored after PRM. Although relapses were observed in 7.5% of individuals, they did not affect HRQoL.This study was presented at the Research Forum of the AAO-HNSF and the Association for Research in Otolaryngology (ARO) Annual Meeting held in Orlando, FL, on September, 23, 2003     

Subjective visual horizontal in patients with posterior canal benign paroxysmal positional vertigo

CONCLUSION: Patients with posterior canal benign paroxysmal positional vertigo (p-BPPV) could have mild excitation in the vestibular system on the affected side. OBJECTIVE: p-BPPV is considered to be caused by small particles dislodged from the utricular macula. While subjective visual horizontal (SVH) mainly reflects utricular function, there is less documentation on SVH in patients with p-BPPV. The purpose of this study was to clarify whether p-BPPV could affect SVH. PATIENTS AND METHODS: Twenty-eight patients with unilateral idiopathic p-BPPV were enrolled. For comparison, 17 patients with vestibular neuritis and 45 patients with cerebello-pontine angle (CPA) tumor were also examined. For measurement of SVH, we used a device that has a red bar of light-emitting diodes (LEDs) in front of the patient. Subjects were asked to rotate the bar to the position that they felt was horizontal in a completely dark room. RESULTS: Deviation of SVH toward the unaffected side down was seen in 82.1% (23/28) of patients with p-BPPV. Mean+/-SD deviation of SVH from the true horizontal to the unaffected side down was 0.49+/-1.21 degrees. Conversely, deviation of SVH was toward the affected side down in 88.2% of patients with vestibular neuritis and in 75.6% of patients with CPA tumor.     

突发性聋继发良性阵发性位置性眩晕的临床观察

目的了解继发于突发性聋的良性阵发性位置性眩晕（benign paroxysmal positional vertigo,BPPV）的发病情况并探讨其治疗策略。方法观察眩晕门诊及耳内科病房中心2004年1月-2010年1月收治的210例突发性聋患者（包括伴有眩晕的突发性聋）合并BPPV的发病情况,并与同期183例原发性BPPV相比较。结果本组突发性聋病例并发BPPV为19．0％（40／210）;40例患者均为高频感音神经性聋或平坦型感音神经性聋。本文40例继发于突发性聋的BPPV,出现时间均在突发性聋发病后t周内。继发性BPPV的手法复位效果与原发性BPPV相似,大多数都于1～2次就诊后治愈。结论突发性聋继发的BPPV是临床常见的现象;继发于突聋的BPPV与原发性BPPV都是以后半规管BPPV多见,并与原发性BPPV手法复位的疗效相似。     

管石复位法治疗良性阵发性位置性眩晕的影响因素分析

目的观察管石复位法治疗良性阵发性位置性眩晕的长期效果，探讨影响治疗预后的相关因素。方法回顾性分析59例后半规管良性阵发性位置性眩晕患者治疗和随访结果．并对管石复位法治疗成功的良性阵发性位置性眩晕患者进行多因素COX回归分析。结果59例患者中有54例（91．5％）治愈。治愈的54例患者在随访中有21例（38．9％）复发，其中有10例患者伴有半规管轻瘫。对患者的性别、年龄、发病时间、病因、半规管功能等指标进行多因素分析，只有半规管轻瘫一项指标进入COX模型，说明半规管轻瘫是影响治疗预后的因素。结论半规管轻瘫是影响BPPV患者管石复位法治疗预后的影响因素。     

Effectiveness of treatment techniques in 923 cases of benign paroxysmal positional vertigo

OBJECTIVE: To present treatment effectiveness of 923 consecutive cases of benign paroxysmal positional vertigo (BPPV) using canalith repositioning, liberatory, and log roll maneuvers combined with redistribution exercises. STUDY DESIGN: Retrospective case review. METHODS: Patients presented with either posterior semicircular canal (P-SCC) BPPV or horizontal semicircular canal (H-SCC) BPPV. Diagnosis was based on patient history of transient paroxysmal vertigo and a positive Dix-Hallpike response with either torsional or horizontal nystagmus. Patients with P-SCC BPPV numbered 840, and 83 patients had H-SCC BPPV. In the original study, there were 1,000 patients; however, 77 patients were dropped from the study because of lack of follow-through. Intervention was canalith repositioning, liberatory maneuvers, log roll maneuvers, and redistribution exercises. Patients numbering 607 were treated with canalith repositioning, 233 patients had liberatory maneuvers, and 83 received log roll maneuvers. All patients received redistribution exercises before treatment maneuvers. After intervention, patients were reassessed at 6 months. RESULTS: There were 601 women and 322 men from ages 12 to 94 (median 55) years. The average duration of symptoms before intervention was 30 months. Outcome measures were considered met when symptoms of BPPV had abated and patients demonstrated a negative Dix-Hallpike response. In the repositioning group, 94% of patients were symptom free or improved, 98% in the liberatory maneuver group and 100% in the log roll group. The average number of sessions was three for all groups. Recurrence of symptoms was demonstrated in 140 (16%) patients at 6 months. CONCLUSIONS: Treatment of BPPV can be effective using either repositioning, liberatory, or log roll maneuvers in combination with redistribution exercises.     

Epley maneuver and the head autorotation test in benign paroxysmal positional vertigo

The head autorotation tests can be affected with the dynamic changes within the semicircular canals caused by benign paroxysmal positional vertigo (BPPV). The vestibular autorotation test is a method of examining the VOR (especially the VOR that develops at higher frequencies like those that occur in the everyday environment). Twenty patients who had been diagnosed as having posterior semicircular canal BPPV were evaluated with head autorotation tests before and after the treatment maneuver. The head autorotation tests were performed just before the use of the Epley maneuver and after the resolution of symptoms and the typical nystagmus pattern. The mean gain values for horizontal rotation tests during the pre-treatment period were 0.823, 0.844, and 0.840 for the frequencies 1, 2, and 3 Hz, respectively. The mean gain values increased by 0.095 (95% confidence interval) with Epley’s maneuver. But this difference difference between the pre-treatment and post-treatment values was not statistically significant. All patients were also evaluated with vertical active tests. The differences between the pre-treatment and post-treatment values were not statistically significant in the vertical autorotation group. The phase values were within normal range in the horizontal and vertical rotation tests and remained so after the Epley maneuver. The stimulation of the VOR caused by BPPV did not affect gain and phase values to a statistically significant degree, and the values noted after the resolution of the patient’s symptoms improved slightly but without statistical significance.     

Dynamics of canal response to head-shaking test in benign paroxysmal positional vertigo

Conclusions. Time constant and maximum slow phase velocity (SPV) of head-shaking nystagmus (HSN) demonstrated a differential canal response to head shaking in 24% of patients with posterior canal benign paroxysmal positional vertigo (BPPV). We suggest that vestibular lithiasis has a limited contribution to the mechanism that generates HSN. Objective. To determine the canal response to head shaking in BPPV. Patients and methods. This was a case-control study including 104 individuals with BPPV. The diagnosis was based on the presence of vertigo and nystagmus during the positional test. Subjects were examined by the horizontal and vertical head-shaking test. Eye movements were recorded on a video camera to analyze the nystagmus. The head was shaken passively in the horizontal and sagittal planes, respectively, for horizontal and vertical HSN at a frequency of 2 Hz. HSN was considered when six consecutive beats of nystagmus with an SPV of at least 2°/s were detected. Main outcome measures were the presence of horizontal and vertical HSN, maximum SPV of HSN, time constant of HSN, and canal paresis. Results. Maximum SPV of vertical HSN was higher in BPPV patients with posterior canal BPPV (n=10) than in controls (p=0.04). Moreover, the time constant of vertical HSN was significantly lower for posterior canal BPPV when compared with controls (p<0.02).     

良性阵发性位置性眩晕的听-前庭功能研究

目的了解良性阵发性位置性眩晕（benign paroxysmal positional veaigo，BPPV）在听和前庭功能检查方面的特点，进一步了解BPPV的可能发病机制，并提出防治策略。方法对86例BPPV患者行纯音测听、高刺激率听性脑干反应、前庭双温试验、前庭诱发的肌源性电位检查。分析BPPV患者几种耳功能检查的阳性率，以及在BPPV发病机制中的作用。结果86例BPPV患者中，原发性占82％（70／86）。纯音测听异常者占52％（45／86）；高刺激听性脑干反应异常者在原发性BPPV中60％（30／50）。前庭诱发的肌源性电位异常为34％（11／32）。前庭双温试验异常者25％（18／72），其中，与BPPV同侧者占67％（12／18）。水平半规管BPPV，双温试验异常者占11％（2／18），后半规管异常者占89％（16／18）。结论原发性BPPV发病率高于继发性BPPV（x^2=67．8140，P〈0．01），纯音测听结果正常与异常的例数几乎相同。高刺激听性脑干反应异常对于原发性BPPV有一定的贡献。水平半规管前庭双温试验异常率低，而后半规管异常率较高。前庭诱发的肌源性电位的异常率明显低于高刺激听性脑干反应和前庭双温试验，说明上迷路的病变与BPPV发病密切相关。鉴于内耳供血可能对BPPV的发病有一定的影响，对于异常的患者应给改善内耳供血的药物，以减少复发。     

Head-tilting stabilometry in patients with benign paroxysmal positional vertigo

OBJECTIVE: One of the pathologic conditions underlying benign paroxysmal positional vertigo (BPPV) is degeneration of the otolith organs. In this study, we examined changes in the parameters of stabilometry under an upright condition and head-tilt conditions in patients with BPPV. METHODS: We performed stabilometry on 21 patients with right BPPV, on 21 patients with left BPPV and on 21 controls. First, the subject stood barefoot in an upright position with both feet together on the platform with eyes closed. Next, tilting of the head about 30 degrees to the left was added. Then, tilting about 30 degrees to the right was performed. RESULTS: In right BPPV patients, the total length of velocity vectors in the right or left direction on right or left head-tilt were significantly smaller than those in an upright position. The enveloped area and total length of velocity vectors in the right or left direction were significantly larger than those in controls. In left BPPV patients, there were no parameters that showed any significant difference. CONCLUSIONS: In this study, lesions of right BPPV patients were coincidentally more severe than those in left BPPV patients, and velocity vectors with head-tilts were significantly smaller than in an upright position. Using the total length of the velocity vectors, head-tilting stabilometry has the potential to become a reliable otolith function examination method.     

Diagnostic problems in patients with benign paroxysmal positional vertigo

The steps of the examination procedure applied for a correct diagnosis of benign paroxysmal positional vertigo (BPPV) are reviewed. A precise diagnosis is important in view of treatment of this type of vertigo by rehabilitation therapy. Clinical experience supports the concept that the diagnosis has to be based not only on a typical history, but also on the presence of a reproducible vertigo and paroxysmal positioning nystagmus. In the procedure applied in the department, this nystagmus can be reproduced by the Dix-Hallpike maneuver under Frenzel's glasses, during electronystagmography (ENG) recording in the position tests, or it can be present in the vestibular habituation training test battery (a battery of 19 maneuvers applied for defining the adequate exercises in the rehabilitation treatment for BPPV). Analysis of the reviewed data in 95 patients showed that one third of the patients described the vertigo in a rather atypical way, while the further testing revealed a typical BPPV. This experience denies any absolute reliability to only history. In fact, only the finding of such a paroxysmal positioning nystagmus is conclusive for confirming BPPV. However, also the presence of such a nystagmus appeared not to be a constant datum, so that in some patients more than one examination was necessary to come to a reliable diagnosis. It is obvious that, for detecting a paroxysmal positioning nystagmus, ENG is less reliable than the Dix-Hallpike maneuver under Frenzel's glasses.     

Experimental model of benign paroxysmal positional vertigo with biphasic nystagmus using isolated semicircular canals

Conclusions: The co-existence of cupulolithiasis and canalolithiasis might be a possible mechanism for the spontaneous inversion of positional nystagmus.

Objective: To investigate the mechanism of spontaneous inversion of nystagmus direction without a positional change in experimental models of co-existing cupulolithiasis and canalolithiasis.

Methods: Co-existing canalolithiasis and cupulolithiasis models were prepared using the bullfrog posterior semicircular canal (PSC). Ten bullfrogs were used. The ampullary nerve discharges were recorded as compound action potentials (CAPs). First, an otoconial mass was placed on the cupula to produce cupulolithiasis. Subsequently, another otoconial mass was introduced into the canal lumen to produce canalolithiasis. Decremental time constants for cupulolithiasis and incremental time constants for canalolithiasis were determined.

Results: At first the CAPs increased and continued for a long time when the cupulolithiasis was generated. Subsequently the CAPs were suppressed by creating canalolithiasis. Finally, the CAPs increased again after the motion of otoconia inside the canal lumen stopped. The decremental time constant for cupulolithiasis was significantly longer than the incremental time constant for canalolithiasis.