Impact of caloric test asymmetry on response to treatment in vestibular migraine.

OBJECTIVE: This study aimed to examine the association between caloric asymmetry and response to treatment in patients with vestibular migraine. METHOD: Dizziness Handicap Inventory scores were compared between patients with less than and more than 25 per cent asymmetry (using Cohen effect size) in a cohort of definite vestibular migraine patients who underwent caloric testing between August 2016 and March 2019. RESULTS: A total of 31 patients (mean age: 48.7 ± 20.0 years; mean follow up: 9.1 ± 8.1 months) were included. Mean caloric asymmetry was 15.1 ± 15.6 per cent, with 6 (19.4 per cent) patients having asymmetry more than 25 per cent. Overall, patients experienced significant improvement in Dizziness Handicap Inventory total (d = 0.623 (95 per cent confidence interval, 0.007, 1.216)), emotional domain (d = 0.635 (95 per cent confidence interval, 0.019, 1.229)) and functional domain (d = 0.769 (95 per cent confidence interval, 0.143, 1.367)) but not physical domain (d = 0.227 (95 per cent confidence interval, -0.370, 0.815)) scores. Patients with more than 25 per cent asymmetry had no significant improvement in Dizziness Handicap Inventory scores, whereas those with less than 25 per cent asymmetry had significant improvement in Dizziness Handicap Inventory functional domain scores only (d = 0.636 (95 per cent confidence interval, 0.004, 1.244)). CONCLUSION: Vestibular migraine patients with peripheral vestibular weakness on caloric testing may be less likely to improve after treatment compared with those without.

Menière's Disease and Caloric Stimulation: Some News from an Old Test.

OBJECTIVES: The aim of the present study was to improve the instrumental diagnosis of assessing Menière's disease (MD) if the frequency and slow-phase velocity (SPV) of the thermally induced nystagmus analyzed through the caloric vestibular test (CVT) showed different alterations in relationship with an increasing severity of the cochlear involvement. MATERIALS AND METHODS: The study retrospectively analyzed the CVT results of 72 patients affected by unilateral "definite MD" according to the 2015 Barany Society Diagnostic Criteria and treated only conservatively. RESULTS: There were 7 (9.72%) patients in stage 1, 27 (37.50%) in stage 2, 35 (48.61%) in stage 3, and 3 (4.16%) in stage 4. The canal paresis (CP) calculated through the frequency of the thermally induced nystagmus on the affected side increased in more severe stages (p=0.033). Conversely, the CP calculated through the SPV was not significantly different among the stages showing abnormal values even in the early phases of the disease (71% in stage 1, 81% in stage 2, 91% in stage 3, and 100% in stage 4), exclusively on the affected side. CONCLUSION: Abnormalities of the thermally induced nystagmus on the affected side characterize most patients with MD, but only "SPV" alterations are common in the early stages. An increasing severity of the cochlear involvement progressively reflects also on the "frequency" parameter. Detecting a dissociation between these two parameters could represent an instrumental marker of the early forms of MD. Cite this article as: Cerchiai N, Navari E, Miccoli M, Casani AP. Menière's Disease and Caloric Stimulation: Some News from an Old Test. J Int Adv Otol 2019; 15(3): 442-6.

The head impulse test as a predictor of videonystagmography caloric test lateralization according to the level of examiner experience: A prospective open-label study.

We conducted a study to compare how well the head impulse test (HIT), without and with eye-movement recordings, would predict videonystagmographic (VNG) caloric test lateralization when performed by a resident and an experienced otoneurologist. This prospective, open-label, blinded study was conducted in an ambulatory tertiary care referral center. Our study population was made up of 60 patients-29 men and 31 women, aged 20 to 82 years (mean: 56.4 ± 11.4)-with peripheral vestibulopathy who underwent HIT and VNG caloric testing. The HIT was conducted in two protocols: HIT0 and HIT1. The HIT0 was performed with passive brisk movements of the patient's head from the 0° null position to 20° sideways, and the HIT1 was performed toward the center while the null position was a 20° head rotation to the right and to the left. Each protocol was carried out without video eye-movement recordings (HIT0 and HIT1) and with such recordings (rHIT0 and rHIT1). The primary outcome measures were (1) a comparison of the HIT's sensitivity and specificity when performed by the resident and by the experienced otoneurologist and (2) the ability of video-recorded HIT to predict VNG caloric test lateralization. The sensitivity and specificity obtained by the resident were 41 and 81%, respectively, for HIT0 and 41 and 90% for HIT1. The sensitivity and specificity obtained by the experienced otoneurologist were 18 and 89% for HIT0 and 32 and 85% for HIT1. Analysis of the recorded eye-movement clips of the HIT0 and HIT1 obtained by a second experienced otoneurologist found a sensitivity and specificity of 32 and 63% for rHIT0 and 33 and 82% for rHIT1. We conclude that the HIT yields high false-negative rates in predicting significant caloric lateralization. Analysis of the eye-movement recordings was no better than normal testing alone for detecting saccades. The experience of the examining physician had no impact on test performance characteristics.

[Correlation between bedside triple test by videonystagmoscope and caloric test].

OBJECTIVE: To investigate the correlation between rapid bedside triple test and caloric test. METHOD: We reviewed clinical records of 313 consecutive patients presenting with vertigo at our ear-nose-throat clinic.RESULTS of bedside vestibular tests in all patients were compared with caloric test. The sensitivity, specificity, and positive and negative predictive values for the triple test relative to caloric test were calculated. RESULTS: Compared with the caloric test results, the sensitivity, specificity, positive predictive value(PPV), and negative predictive value(NPV) of the triple test were 65.1%, 94.0%, 90.5% and 75.5%, respectively. CONCLUSIONS: As a predictive screening for patients with vertigo, the bedside triple test is a rapid, reliable tool for clinical diagnosis.

Posterior semicircular canal occlusion for intractable benign positional vertigo: outcome in 55 ears in 53 patients operated upon over 20 years.

OBJECTIVE: To report the outcome of posterior semicircular canal occlusion surgery for intractable benign positional vertigo, regarding vertigo cure rate and hearing and balance outcomes. METHODS: Retrospective review of 53 patients presenting with benign positional vertigo, unresponsive to repositioning manoeuvres, who eventually underwent posterior canal occlusion, over a 20 year period. RESULTS: From 1991 to 2011, 5364 benign positional vertigo patients were treated in our balance disorders clinic; 53 of those who failed to respond to repositioning underwent posterior canal occlusion. All 53 were cured of their benign positional vertigo. Nine suffered some symptomatic permanent hearing loss (>20 dB at low and >25 dB at high frequencies). Ten patients suffered caloric vestibular function deterioration, with mild but permanent subjective imbalance in five; a further 10 patients with no post-operative caloric test changes also had some permanent imbalance. Benign positional vertigo later developed in the operated ear lateral canal in two patients and in the opposite ear posterior canal in eight patients. Two patients needed bilateral sequential posterior canal occlusion. CONCLUSION: Posterior canal occlusion is a highly effective treatment for intractable benign positional vertigo, with what is probably an acceptable risk to hearing and balance: five of six patients will have no hearing problem and nine of 10 no balance problem after surgery.

Ocular counterrolling: an indicator of bilateral vestibulopathy.

The ocular counterrolling can be static or dynamic. The purpose of this work is to connect the clinical absence of dynamic ocular counterrolling with bilateral caloric paresis. A prospective study on 216 patients in whom the absence of dynamic ocular counterrolling was tested and standard caloric test was performed. The cut-off value for bilateral caloric paresis is an absolute reflectivity of 10 in nystagmic frequency and 8 in slow phase velocity. The adequate contingency tables were constructed and tests of Chi-squared calculated. Sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, and area under receiver operating characteristic (ROC) curve were also calculated. Using the reflectivity according to the nystagmic frequency, we obtained P = 0.000 for Chi-squared, area under ROC curve was 0.832 and positive likelihood ratio 11.47. For slow-phase velocity, the results were P = 0.000, area ROC of 0.735 and positive likelihood ratio 9.43. There is a statistically significant connection between the clinical absence of dynamic ocular counterrolling and bilateral caloric paresis, with a strong diagnostic power. The mechanisms by which this phenomenon can be attributed to canalicular damage instead of otolithic damage are discussed.

A comparison of water and air caloric responses and their ability to distinguish between patients with normal and impaired ears.

OBJECTIVES: The caloric test is a mainstay of modern vestibular assessment. Yet caloric test methods have not been well standardized, and normal response values have not been universally agreed upon. The air caloric test has been particularly problematic. In this article, we present our efforts to establish a population-based description of the caloric response evoked by water and air stimuli at both cool and warm temperatures. DESIGN: Data were collected from a retrospective record review of patients who underwent caloric testing at Mayo Clinic Jacksonville between 2002 and 2006. Two subgroups were identified. One group was found to have no vestibulopathy after comprehensive medical investigation. The second group was found to have severe bilateral vestibular weakness; this diagnosis was based on medical evaluation and objective test results. Caloric response distributions and associated probability estimates were developed from each group. RESULTS: A total of 2587 medical records were found to contain caloric response data. Of these, 693 patients met the criteria to be classified as having no identifiable vestibulopathy (otologically normal patients with normal caloric responses). Sixty-eight patients met the criteria for bilateral vestibular weakness (reduced or absent rotatory chair responses). Our analysis yielded the following results: (1) there were differences between nystagmus distributions across stimuli. On average, the magnitude of cool water (30 degrees C) maximum slow-phase velocities was smaller than those from warm water (44 degrees C). Maximum slow-phase velocity distributions from cool (21 degrees C) and warm (51 degrees C) air stimuli were more similar to each other than were responses to water stimuli and fell between the water distributions. (2) Combined metrics (combined eye speed and total eye speed) were comparable for water and air stimuli. (3) Response distributions from otologically normal patients were different from those of patients with bilateral vestibular weakness. (4) Derived probability estimates allowed for quantification of caloric response normal limits, sensitivity, specificity, and error rates. CONCLUSIONS: Current bithermal test methods assume an equivalence of caloric response strength from warm and cool stimuli. Our results show standard cool and warm water stimuli provoke substantially different response magnitudes, with warm stimuli provoking stronger responses. When calibrated as described herein, air stimuli perform comparably with water stimuli for bithermal caloric test purposes, with more uniform and less variable response distributions. Both air- and water-based tests were able to distinguish between normal and abnormally weak ears with sensitivity and specificity values between 0.82 and 0.84. We advocate for the calibration of all caloric stimuli based on the test's statistical performance and not arbitrary assumptions about stimulus equivalence.

Otolith dysfunction in vestibular neuritis: recovery pattern and a predictor of symptom recovery.

OBJECTIVES: To prospectively follow patients with vestibular neuritis (VN), to compare the recovery pattern of canal and otolith dysfunction, and to determine which tests best predict symptom recovery. METHODS: Between March 2006 and December 2006, 51 consecutive patients with unilateral VN were enrolled within 7 days of onset (average 3 days). Otolith function tests included ocular torsion (OT), subjective visual vertical (SVV), and vestibular evoked myogenic potential (VEMP), and canal function tests included head-shaking nystagmus (HSN), caloric stimulation, and head-thrust testing. Patients returned for two follow-up evaluations at approximately 1 week and 6 weeks after the initial evaluation. RESULTS: On the first examination, all patients had abnormal HSN, caloric, and head-thrust test results, and at least one otolith-related test abnormality: abnormal tilt of SVV (48/51, 94%), abnormal OT (42/51, 82%), or abnormal VEMPs (25/51, 49%). The degree of SVV tilts correlated with the degree of OT for one or both eyes (p < 0.05). Skew deviation was observed in 7 patients (14%), and a complete ocular tilt reaction was detected in only 2 patients. On follow-up, otolith test results returned to normal more rapidly than canal test results. The head-thrust test was the best predictor of symptom recovery. Eighty percent of patients who continued to report dizziness at the last follow-up visit had a positive head-thrust test result, whereas only 10% of patients who were not dizzy had a positive head-thrust test result. CONCLUSION: Otolith-related test abnormalities improve more rapidly than canal-related test abnormalities after vestibular neuritis. If patients have a positive head-thrust test result on follow-up, they are more likely to be dizzy.

Physical activity after retirement enhances vestibulo-ocular reflex in elderly humans.

Vestibular information decreases in sensitivity with ageing, and its role becomes less important in the regulation of postural control. In addition, the practice of physical activity (PA) helps to improve vestibular sensitivity. This study aimed to evaluate PA-related benefit on vestibular function in 36 subjects split into four groups according to the period of practice. Caloric and rotatory vestibular testings showed that the performance of subjects who had begun practising PA recently were close to those of subjects active for a long time, whereas those of subjects who had stopped practising at an early age were close to those of inactive subjects. Although starting to practise PA has immediate beneficial effects on the vestibule, in terms of vestibular stimulation mechanisms these effects soon disappear if this activity is stopped.

Contribution of the vertical semicircular canals to the caloric nystagmus.

Modulation of the caloric nystagmus in response to repositioning the plane of one vertical semicircular canal from gravitational horizontal to vertical during continuous caloric stimulation was used to measure the vertical canal's contribution to the nystagmus. The rationale was to examine the thermovective response from one vertical canal at a time, after a temperature gradient had been established across its two limbs. The nystagmus was measured and analysed in three dimensions using orthogonal head-referenced coordinates. The magnitude of each semicircular canal's contribution to the overall caloric response, the canal vector, was determined in non-orthogonal, contravariant semicircular canal plane coordinates. By using the canal plane reorientation technique and contravariant canal plane coordinates, we were able to measure the proportional thermovective response magnitude generated by each vertical canal during caloric stimulation. We found that the anterior canal contributed about one-third and the posterior canal about one-tenth as much as the lateral canal did to the overall caloric response magnitude when it was reoriented from horizontal to vertical. Comparison of the eye rotation axis before and after each vertical canal plane reorientation, with the geometry of the stimulated semicircular canals, also showed directional modulation of the caloric nystagmus by the vertical canal response. When one vertical canal plane was horizontal during caloric stimulation, the eye rotation axis aligned with the resultant of the other vertical canal and the lateral canal response axes. After vertical canal plane reorientation, the eye rotation axis realigned towards the resultant of the maximally stimulated vertical canal and the lateral canal, by 55.2+/-33.9 degrees (mean+/-SD) after anterior canal plane reorientation and by 32.3+/-21.2 degrees after posterior canal reorientation.

[The effect of Lasix on nystagmus in the caloric and optokinetic tests in Menière's disease]. / Vliianie laziksa na nistagm v kaloricheskom i optokineticheskom testakh pri bolezni Men'era.

The study was made of labyrinthine changes induced by lasix dehydration. Changes indicative of Meniere's disease were identified at comparison of the findings obtained by audiological lasix test, caloric optokinetic reactions. Four types of the nystagmic response in the bithermal lasix-test were determined. These reactions are helpful for more precise staging of the disease.

Reappraisal of the monothermal warm caloric screening test.

The usefulness of a monothermal warm caloric screening test (MWST) for predicting alternate binaural bithermal test abnormalities has been reexamined. Previously, researchers have reported false-negative rates for the MWST ranging from 0% to over 35%. Alternate binaural bithermal test data from 504 consecutive patients were evaluated with MWST failure criteria of 24.5% and 29%, with and without the addition of failure criteria from subtests of the electronystagmography examination. Sensitivity of the MWST alone was high, and improved with additional failure criteria. The specificity levels were correspondingly high. Results support the use of the MWST with adjunctive failure criteria when patients have otherwise normal electronystagmography findings.

Chaos theory applied to the caloric response of the vestibular system.

Developments in the field of nonlinear dynamics has given us a new conceptual framework for understanding the mechanisms involved in the regulation of complex nonlinear systems. This concept, called "chaos" or "deterministic chaos," has been applied to EKG, EEG, and other physiological signals, but not yet to the ENG signal. The underlying geometrical structure in chaotic dynamics is fractal (noninteger dimension), and calculating the fractal dimension of the electronystagmographic recording from caloric testing gave a dimension ranging from 3.3 to 7.7. This result demonstrates that the multidimensional vestibular system, with its numerous neurological pathways, can somehow reduce the degrees of freedom and give rise to an irregular dynamic low-dimensional behavior, which is associated with deterministic chaos.

Effects of interstimulus interval on slow phase velocity to ipsilateral warm air caloric stimulation in normal subjects.

This study investigated the effects of interstimulus interval on slow phase velocity (SPV) to ipsilateral warm air caloric stimulation in normal subjects. Results suggest that about 3 minutes should intervene between the offset of one irrigation and the onset of the second irrigation. This finding supports the hypothesis that carryover effects are likely only when nystagmus from the preceding irrigation overlaps the subsequent irrigation. If correct, clinicians do not have to wait a fixed time period between stimuli, but can initiate caloric stimulation as soon as nystagmus has ceased from the preceding irrigation. This recommendation compensates for individual and procedural differences. Test-retest reliability also was investigated. Findings suggest that when immediate test-retest differences exceed approximately 6 degrees/second (95% confidence interval), the examiner should administer additional trials until stability is ascertained. Moreover, unusual or significant findings should be verified with repeat testing.

Prediction of bithermal caloric response from monothermal stimulation.

The use of either cold or warm caloric stimulation alone as a screening tool for unilateral weakness has been suggested as a means of both shortening testing time and reducing patient discomfort. The validity of the monothermal caloric test must be well established before it can be routinely used in clinical situations. The purpose of this investigation was to re-evaluate the monothermal caloric test by examining the correlations between unilateral weakness derived from bithermal caloric stimulation compared to monothermal caloric results using either warm or cool stimulation alone. A retrospective analysis of 200 patients indicated significant correlations between bithermal and monothermal unilateral weakness for patients with unilateral weakness of less than 15% and greater than 30% for both warm and cool water stimulation. For patients with 15% to 30% unilateral weakness, the bithermal and monothermal calorics were significantly correlated for only the cool condition. When predicting normal or greater than 20% unilateral weakness, either of the monothermal calorics have greater than 85% efficiency, with specificity greater than 94% and sensitivity greater than 64%. However, the false-negative rate is 29% for warm and 36% for cool calorics. The high rate of false-negative findings indicates that screening tests have no place in a diagnostic battery, especially in view of the implications for missing significant pathology.