Maximum Slow Phase Velocity Research Articles

Feature of semicircular canal function in obstructive sleep apnea-hypopnea syndrome

The aim of this study was to evaluate the effects of obstructive sleep apnea-hypopnea syndrome (OSAHS) on semicircular canal function. By means of a series prospective study at Department of Otolaryngology Head and Neck Surgery of our hospital, the study was performed on 77 patients suffering from OSAHS in a period from 2012 to 2014, who underwent polysomnography (PSG) and caloric test. The maximal slow-phase velocity (SPV) and unilateral weakness (UW) were used to measure the vestibular function. Severity of OSAHS was evaluated by the lowest oxygen saturation (LSaO₂) and apnea hypopnea index (AHI). The SPV after cool was signed, warm test was performed for each ear, and the sum of left ear SPV were calculated, and then, the SPV of right ear was counted as the same way. Finally, the relationships between LSaO₂, AHI, age, BMI, and SPV of caloric test were analyzed. Caloric vestibular tests in the 77 OSAHS patients demonstrated abnormal findings in 52 patients (67.5%) and normal vestibular functions in the remaining 25 patients (32.5%). Of the 52 patients with an abnormal test result, 16 (20.8%) patients had unilateral vestibular hyporeflexia and 36 (46.7%) patients revealed a bilateral vestibular hyporeflexia. There was no linear relationship between AHI, age, BMI with SPV of caloric test (P > 0.05). The SPV had significant difference between Lower LSaO₂group (LSaO₂< 50%) and higher LSaO₂group (LSaO₂≥ 80%) (P < 0.05). LSaO₂was lower in patients undertaken bilateral vestibular hyporeflexia. OSAHS patients with long-term intermittent hypoxia can disturb the vestibular organs and reduce semicircular canal function. The heavier hypoxemia will lead to the lower reflex of semicircular canal, with the heavier degree of hypoxemia, and the bilateral horizontal semicircular canal involvement may also be higher at the same time. Due to the effect of vestibule centre compensatory, OSAHS patients lack of dizziness and symptoms from balance disturbances such as typically acute vestibular damage.

急性めまい症例に対して即時に行う温度刺激検査の有効性についての検討

I investigated the effectiveness of the immediate caloric test for acute vertigo cases. I was able to diagnose 21 (29.5%) cases of vestibular neuronitis immediately by performing a caloric test in 71 acute vertigo cases. I confirmed that as an effect of the steroid dosage on vestibular neuritis, the maximum slow phase velocity of the nystagmus significantly improved after the steroid dosage from the second week, and the obstacles to everyday life due to the vertigo using DHI (Dizziness Handicap Inventory) significantly improved from the fourth week. I made the first medical examination within 30 days from the onset and, for vestibular neuronitis cases in which treatment was started, the effect of the steroid treatment was significantly seen in all cases. I diagnosed vestibular neuronitis by performing a caloric test for the acute vertigo cases immediately, and starting treatment promptly was believed to be required.

The second and third phases of caloric nystagmus

Conclusion: The second and third phases of caloric nystagmus occur at a high rate. We can explain this phenomenon based on the hydrostatic pressure theory involved in perilymph. Objectives: To clarify the incidence of the second and third phases of caloric nystagmus, and to measure their intensity. Methods: The subjects were 12 healthy humans. The right ear was stimulated using iced water. The first phase of caloric nystagmus was recorded in a supine position. Immediately after the cessation of the first phase, each subject was repositioned to a prone position, and the second phase was recorded. Immediately after the halt of the second phase, each subject was repositioned to a supine position, and the third phase was recorded. Nystagmus was analyzed using three-dimensional video-oculography. Results: The mean value of maximum slow-phase velocity (MSV) of the first phase was 27.2°/s. All subjects revealed the second phase, and the direction was toward the right. The mean value of MSV was 7.2°/s. Nine subjects (75%) showed the third phase, and the direction was toward the left. The mean value of MSV was 2.7°/s.

脊髄小脳失調症3型 (Machado-Joseph 病) における神経耳科学的所見

In recent years, a definitive diagnosis of spinocerebellar ataxia type 3, also known as Machado-Joseph disease (SCA3/MJD), has become possible at an early stage with the development of a gene analysis method. We retrospectively investigated the otoneurological findings of 56 patients (male, 23 patients; female, 33 patients) who had been definitively diagnosed as having SCA3/MJD by gene information retrieval at Tokyo Metropolitan Neurological Hospital. In SCA3/MJD patients, the incidence of abnormal oto-neurological findings, e.g., upgaze palsy, gaze nystagmus, impaired optokinetic nystagmus (OKN), smooth pursuit, and saccade, reduced bilateral vestibulo-ocular reflex (VOR), and impaired visual suppression of VOR, was high. 12 of 56 patients had horizontal gaze palsy, so that those 12 cases were excluded from the later investigation. The reduced bilateral VOR performed by caloric response with cold and/or iced water was observed in 31 of 56 ears within six years of the disease; however, it was observed in all 32 ears of patients who had developed SCA3/MJD more than six years previously. Therefore, reduced bilateral VOR is considered to be a very useful biomarker of SCA3/MJD in clinical diagnosis, especially at six years or more since the onset of the disease. Moreover, the otoneurological findings in the markedly reduced VOR group (six patients) and normal VOR group (six patients) within six years after onset of the disease was investigated. In the markedly reduced VOR group, the incidence of upgaze palsy was higher, the impaired visual suppression of VOR was more advanced, and the mean maximum slow phase velocity of OKN was lower in comparison with the normal VOR group. It could indicate that the brainstem dysfunctions were more severe in the markedly reduced VOR group than in the normal VOR group. This may account for the fact that the bilateral VOR dysfunction in patients with SCA3/MJD may be due to a disorder in the central vestibular system originating from the VOR pathways.

The Significance of 180-Degree Head Rotation in Supine Roll Test for Horizontal Canal Benign Paroxysmal Positional Vertigo

The relatively low success rate of the treatment maneuver for horizontal semicircular canal (HSC) benign paroxysmal positional vertigo (BPPV) may be caused by the difficulty determining the affected side. We developed a 180-degree supine roll test (SRT) by modifying the 90-degree SRT to increase diagnostic accuracy and evaluated its significance. A prospective study. Tertiary referral center. A total of 122 patients with HSC-BPPV performed both the 90- and 180-degree SRTs. The affected side was determined by the 90- and 180-degree SRTs. The bow and lean (BL) test was also performed in cases with ambiguous or opposite results on both SRTs. A comparison of the difference in slow phase velocity (SPV) of nystagmus among the 90- and 180-degree SRTs and BL test. The maximum SPV of nystagmus during the 180-degree SRT was significantly greater than that during the 90-degree SRT. The SPV difference was less in the 180-degree SRT than that in the 90-degree SRT. Although the 180-degree SRT showed fewer meaningful results (n = 65) than the 90-degree SRT (n = 71), the affected side was determined by the 180-degree SRT in 15 cases with ambiguous results on the 90-degree SRT. Among 10 cases showing opposite results, 7 were identified by the BL test. Five (71.4%) of 7 cases had consistent affected sides with the 180-degree SRT. The 180-degree SRT can be an additional method when it is difficult to determine the affected side from the 90-degree SRT.

Cupulolithiasis of the posterior semicircular canal

BackgroundWe sometimes experience patients with persistent torsional/vertical (upbeating) positional nystagmus in the head-hanging position. We have been convinced of the existence of cupulolithiasis of the posterior semicircular canal because such cases reveal persistent torsional/vertical (downbeating) positional nystagmus in the nose-down position. PurposeIn order to confirm the validity of Ewald's third law, we quantified the difference between positional nystagmus in the head-hanging position and that in the nose-down position. MethodsThe subjects were 10 patients with posterior cupulolithiasis, 9 female and 1 male, with a mean age of 58.9years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed three-dimensional video-oculography and measured the maximum slow-phase velocity (MSV) of three components. ResultsIn the horizontal component, the mean value of MSV in the head-hanging position was 3°/s, and that in the nose-down position was 2.7°/s. There was no significant difference between the two positions. In the vertical component, the mean value of MSV in the head-hanging position was 4.3°/s, and that in the nose-down position was 6°/s. There was no significant difference between the two positions. In the torsional component, the mean value of MSV in the head-hanging position was 4.4°/s, and that in the nose-down position was 1.4°/s. The former was significantly greater than the latter (p<0.01). ConclusionsAlthough we could not confirm the validity of Ewald's third law, the torsional component in the head-hanging position was significantly greater than that in the nose-down position.

Visuo-Oculomotor Deficiency at Early-Stage Idiopathic Scoliosis in Adolescent Girls

Cross-sectional study. To determine whether adolescent idiopathic scoliosis (AIS) at onset is associated with oculomotor dysfunction and whether these oculomotor anomalies are correlated to the amplitude of the spine deformation. AIS is related to abnormalities of postural control. To date, few studies have focused on visuo-oculomotor and vestibulo-ocular functions at early-stage AIS. Fifty-three adolescent girls were diagnosed with AIS (mean age: 11.6 ± 2.1 yr) on clinical and radiological criteria (mean Cobb angle: 14.8° ± 5.0°). Visuo-oculomotor and vestibulo-ocular functions were studied with video-oculography, including saccades, smooth pursuit, caloric test, and pendular rotation, with visual vestibular ocular reflex and vestibulo-ocular reflex sequences. Two patient groups were defined according to the mean Cobb angle: group 1 included 29 patients with a Cobb angle from 5° to 14° and group 2 included 24 patients with a Cobb angle from 15° to 25°. The group 2 showed different saccade characteristics than group 1: higher latencies for saccade sequences characterized by temporal uncertainty and predictive direction; lower velocity regardless of the type of the saccades. No difference was observed for saccadic accuracy and smooth-pursuit gain. For the visual vestibular ocular reflex, group 2 showed lower total maximal slow-phase velocity than group 1, whereas the vestibulo-ocular reflex (tested in dark) did not differ between groups. No difference was observed concerning the caloric vestibular test. Patients with a Cobb angle of 15° or more presented normal vestibulo-ocular responses but altered visuo-oculomotor functions, especially for the saccadic latency and velocity. This could be the result of a dysfunction of oculomotor pathways at cerebellar and/or brainstem level. These central disorders may be incriminated in the development of AIS.

Asymmetry of positioning nystagmus in posterior canalolithiasis

Conclusions: Ewald's third law is correct in the posterior semicircular canal and the intensity of stimulatory nystagmus is 2.7 times as strong as that of inhibitory nystagmus. Objectives: Ewald's third law states that a flow of endolymph away from the ampulla causes more stimulation than a flow toward the ampulla in the posterior canal. The aims of this study were to quantify the asymmetry of positioning nystagmus in posterior canalolithiasis and to confirm the validity of Ewald's third law. Methods: Subjects were 20 patients who revealed typical vertical/torsional positioning nystagmus in the Dix–Hallpike test, 14 females and 6 males, with a mean age of 55.2 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed three-dimensional video-oculography and measured maximum slow-phase velocity of three components (horizontal, vertical, and torsional). Results: The mean value of maximum slow-phase velocity (sum of three components) in the head-hanging position was 42.3°/s and that in the sitting position was 15.6°/s. The former was significantly greater than the latter (p < 0.01).

Persistent direction-changing geotropic positional nystagmus

The aims of the study were to clarify whether persistent direction-changing geotropic positional nystagmus contains vertical and torsional components, and to quantify the asymmetry. We analyzed nystagmus in four positions (healthy-ear-down, affected-ear-down, supine, nose-down) using three-dimensional video-oculography. Subjects were 18 patients with persistent direction-changing geotropic positional nystagmus, 16 females and 2 males, with a mean age of 55 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed three-dimensional video-oculography and measured maximum slow-phase velocity (MSV) of three components. Positional nystagmus was not purely horizontal. Eight (44%) patients revealed a vertical component (upward) and 15 (83%) patients had a torsional component in the healthy-ear-down position. Seven (39%) patients revealed a vertical component (downward) and 10 (56%) patients showed a torsional component in the nose-down position. The mean value of MSV of the horizontal component in the supine position was 9.3°/s and that in the nose-down position was 15.7°/s. The latter was significantly greater than the former (p < 0.05). Eye movements in the supine position and the nose-down position were not mirror images. These results suggest that vertical and torsional components occur from the horizontal semicircular canal, and that horizontal canal ocular reflex is influenced by input from the otolithic organs.

Cupulolithiasis of the horizontal semicircular canal

To clarify whether positional nystagmus of horizontal cupulolithiasis contains vertical and torsional components, and to quantify the asymmetry, we analyzed nystagmus in four positions (healthy-ear-down, affected-ear-down, supine, nose-down), using 3-dimensional video-oculography. Subjects were 20 patients with direction-changing apogeotropic positional nystagmus, 11 females and 9 males, with a mean age of 58.1 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed 3-dimensional video-oculography and measured maximum slow-phase velocity (MSV) of three components. Positional nystagmus was not purely horizontal. Eleven (55%) patients revealed a vertical component, and 14 (70%) patients had a torsional component in the healthy-ear-down position. The mean value of MSV of the horizontal component in the healthy-ear-down position was 18°/s and that in the affected-ear-down position was 7.8°/s. For the horizontal component, MSV in the healthy-ear-down position was significantly greater than that in the affected-ear-down position (p < 0.01). These results suggest that vertical and torsional components occur from the horizontal semicircular canal, and the response to ampullopetal bending is more than two times as strong as that to ampullofugal bending.

Positional nystagmus of horizontal canalolithiasis

AbstactConclusion: Vertical and torsional components occur from the horizontal semicircular canal, and the response to ampullopetal flow is greater than that to ampullofugal flow in every component. Objectives: To clarify whether positional nystagmus of horizontal canalolithiasis contains vertical and torsional components, and to quantify the asymmetry of nystagmus. Methods: Twenty patients with transient direction-changing geotropic positional nystagmus were examined, and we performed three-dimensional video-oculography and measured the maximum slow-phase velocity (MSV) of three components. Results: Positional nystagmus was not purely horizontal. Fifteen (75%) patients revealed a vertical component and 19 (95%) patients had a torsional component. The mean value of MSV of the horizontal component in the affected-ear-down position was 51.5°/s and that in the healthy-ear-down position was 19.1°/s. The mean value of MSV of the vertical component in the affected-ear-down position was 8.7°/s and that in the healthy-ear-down position was 3.0°/s. The mean value of MSV of the torsional component in the affected-ear-down position was 12.8°/s and that in the healthy-ear-down position was 6.5°/s. For every component, MSV in the affected-ear-down position was significantly greater than that in the healthy-ear-down position (p < 0.01).

Perverted head shaking nystagmus in focal pontine infarction

Although several papers have been published on perverted head shaking nystagmus (PHSN) associated with focal brainstem or cerebellar lesion, there are no reports of a focal pontine infarct that causes PHSN. We report a patient with focal pontine infarction who presented with sustained dizziness, limb dysmetria on the left extremity, decreased sensations to position and vibration of the left extremity, and gait imbalance. Only vestibular abnormality was downbeat nystagmus after vigorous head shakings. The maximum slow phase velocity of PHSN was 26°/s, and its duration was about 20 s. This is the first report of PHSN associated with focal pontine infarction. Crossed ventral tegmental tract and velocity storage mechanism of vestibulocerebellum might be related on PHSN in this case.

Test-retest reliability of vibration-induced nystagmus in peripheral dizzy patients

The purpose of this study was to analyze test-retest reliability of vibration-induced nystagmus (VIN) in dizzy patients. Fifty-two consecutive patients with positive eye movements induced by vibration at all four different stimulation sites were enrolled. Evaluation of VIN was repeated in 2 separate sessions, 30 minutes apart. Maximum slow-phase eye velocities at different sites from the first and second sessions were assessed via the intraclass correlation coefficient (ICC) and the Pearson correlation coefficient. The incidence of directional changing of evoked nystagmus and the abnormal rates were also evaluated. Excellent reliability with ICC values ranging from 0.89-0.98 and substantial-to-excellent correlation was obtained for the maximum slow-phase eye velocities at different sites. The incidence of directional changes of evoked nystagmus was 0%-4% at each stimulation site. Forty-three patients (83%) had abnormal results in the first session and 41 patients (79%) had abnormal results in the second session. Overall, the direction and maximum slow-phase eye velocities of VIN for different stimulation sites had excellent test-retest reliability. The VIN test is a reliable test for detecting vestibular imbalance in evaluating a dizzy patient.

Positional nystagmus reversing from geotropic to apogeotropic: a new central vestibular syndrome

Central positional paroxysmal vertigo (CPPV) is rarely encountered in clinical practice. It must be distinguished from the more frequent benign positional paroxysmal vertigo (BPPV) [1, 2] and only an accurate clinical evaluation can identify it. Mostly, CPPV is due to cerebellar disease from various aetiologies, including neoplasm, as in the case reported here [3–5]. In this patient, clinical examination with video-oculography revealed right beating horizontal nystagmus in the right lateral head position (geotropic nystagmus) that reversed direction (to apogeotropic nystagmus) while the head position was maintained. In the left lateral position, the patient had again geotropic nystagmus reversing to apogeotropic nystagmus. Brain imaging revealed the presence of a right hemisphere cerebellar neoplasm causing compression of the IV ventricle and hence the vestibular disturbance. A 50-year-old female patient was referred to our neurootology service because of imbalance and vertigo subacutely developed a fortnight earlier. She had a history of breast cancer treated with surgery in May 1997, followed by adjuvant chemotherapy and hormone therapy. Neurological examination revealed a retropulsion in Romberg position and a backward displacement on the Fukuda stepping test. Coordination was only mildly impaired, with limb dysmetria on right finger-to-nose test. Cranial nerves were intact. Tendon reflexes were symmetrical with flexor plantar responses. Video-oculography showed no spontaneous nystagmus in primary position and no gaze-evoked nystagmus was revealed. Head-shaking test was normal. A slight delay was observed on the horizontal head impulse test toward the right side. Upon slowly positioning the patient in the right lateral head position, first-phase nystagmus manifested itself as right beating paroxysmal nystagmus (geotropic) without any latency. It gradually diminished, only to reverse its direction after about 10 s with the development of left beating (apogeotropic) second-phase nystagmus, as shown in the video (Online resource 1). On the left side, a similar, although less intense, geotropic nystagmus was observed. It reversed its direction in about 20 s, changing to apogeotropic nystagmus, as shown in the video (Online resource 2). Recording of the nystagmus activity revealed a maximal slow-phase velocity (SPV) of 19.6 /s for right geotropic nystagmus, while on the left side it showed an SPV of 8.6 /s. First-phase nystagmus was more intense both on the right and left sides, although it didn’t last as long as secondary apogeotropic nystagmus (Fig. 1). When tested in the straight head-hanging position, no nystagmus was detected. Electronic supplementary material The online version of this article (doi:10.1007/s00415-010-5701-6) contains supplementary material, which is available to authorized users.

Nystagmus parameters and subtypes of benign paroxysmal positional vertigo

Conclusion: Although computational models suggest the existence of canalithiasis and cupulolithiasis subtypes of benign paroxysmal positional vertigo (BPPV), these subtypes cannot be distinguished from each other based on characteristics of nystagmus. Therefore, although the subtypes probably exist more information is needed from each patient than is available without invasive procedures. Also, some patients may have clinical syndromes that include both canalithiasis and cupulolithiasis subtypes. Objective: To determine if the parameters of nystagmus provide sufficient information to determine the subtype of nystagmus in a patient with BPPV. Methods: Patients (n = 118) had unilateral BPPV of the posterior canal; 15 patients also had BPPV of the lateral canal. The main outcome measures were parameters of nystagmus in response to the Dix-Hallpike maneuver: latency to onset of nystagmus, maximum slow phase velocity, and maximum duration. Results: Correlations between pairs of variables showed minimal or no relationships. Also, cluster analyses showed no significant subtypes. The contralateral eye moved significantly faster than the ipsilateral eye.

Heart rate and blood pressure effects during caloric vestibular testing

To determine whether the caloric vestibular test causes significant changes in heart rate and mean arterial blood pressure. Changes in heart rate and mean arterial blood pressure before and after caloric irrigation were compared with the degree of nystagmus (as measured by maximum slow phase velocity) and the patient's subjective dizziness (scored from 0 to 10). A cardiologist reviewed each patient's heart rate and mean arterial blood pressure changes. Patients' anxiety levels were also assessed. Eighteen patients were recruited. There were no adverse events in any patient. There were no overall significant differences between the heart rate and mean arterial pressure before and after each irrigation. There was a significant correlation between the maximum slow phase velocity and patients' subjective dizziness scores. Heart rate and mean arterial blood pressure are not significantly influenced by the caloric vestibular test. This preliminary study will enable patients with stable cardiovascular disease to be recruited for further risk determination.

Time Course of Vestibular Function Changes of Experimental Endolymphatic Hydrops in Guinea Pigs

Objective: To investigate the relationship between endolymphatic hydrops and vestibular dysfunction. Methods: 20 pigmented guinea pigs were used: 15 for a hydrops group and 5 for a sham group. Endolymphatic hydrops was produced by electrocauterization of the endolymphatic sac on the left ears. In the horizontal vestibuloocular reflex (HVOR) study, HVOR responses were recorded before and 1, 2, and 4 weeks after surgery in 9 animals of the hydrops group and 5 animals of the sham group. HVOR gain under sinusoidal rotation with a maximal head velocity of 45°/s and frequencies of 0.05, 0.1, 0.2, 0.4 and 0.8 Hz was analyzed. In the nystagmus study, spontaneous nystagmus was recorded in all animals of the hydrops and the sham groups for 1 h in the dark and the maximum slow-phase velocity was measured before and 1, 2, 4 weeks after surgery. Morphological changes in the inner ear were measured light microscopically. Results: In the hydrops group, the HVOR gains at all stimulation frequencies seemed to decrease 1 week after surgery and recover 2 or 4 weeks after surgery; however, there were no statistical differences among HVOR gains in any periods after surgery. The incidence of spontaneous nystagmus gradually increased after surgery and the direction and onset showed large variation. The duration of nystagmus was approximately 10 min. The degree of endolymphatic hydrops showed large variation. In the sham group, HVOR gains at all stimulation frequencies showed no statistically different change in any period after surgery. In the sham group, no animal showed spontaneous nystagmus. Conclusion: Experimentally induced endolymphatic hydrops seems to contribute to vestibular dysfunction to some extent. We speculated that when endolymphatic hydrops is progressing, vestibular dysfunction might occur.

Reversal of Initial Positioning Nystagmus in Benign Paroxysmal Positional Vertigo Involving the Horizontal Canal

In benign paroxysmal positional vertigo (BPPV), spontaneous reversal of the initial positioning nystagmus rarely occurs without further position changes. We analyzed the characteristics of spontaneous reversal of the initial head-turning nystagmus in 21 patients with BPPV involving the horizontal semicircular canal. All patients showed initial geotropic nystagmus (first-phase nystagmus) on head turning to either side while supine, which was followed by spontaneous reversal (second-phase nystagmus). The reversal was either unilateral (n = 16) or bilateral (n = 5). The maximal slow phase velocity (SPV) and duration of the first-phase nystagmus were greater and shorter than those of the second-phase nystagmus. The reversal group showed greater maximal SPVs of the initial nystagmus in either ipsi- or contralesional direction than the control group. BPPV resolved after particle repositioning maneuver (PRM) in most patients. However, one patient showed persistent apogeotropic nystagmus after PRM. Short-term adaptation of the vestibulo-ocular reflex seems to be the main mechanism of spontaneous reversal of the initial positioning nystagmus. However, coexistence of canalo- and cupulolithiasis should be considered in the patient showing bilateral spontaneous reversal.

The ice-water caloric test

Conclusions: Three possible results are commonly seen after ice-water caloric irrigation and to correctly interpret them the function of the corresponding vestibular receptor and of normal endolymphatic flow must be taken into account. Bedside vestibular examination helps to interpret discrepant findings. Objective: To review the findings obtained with the ice-water caloric test in patients with dizziness and to compare the results with those of the bedside test. Patients and methods: The study was undertaken in a university hospital, tertiary medical center. The indications to perform the ice-water caloric test were: 1) unilateral canal weakness >90%; 2) a maximum slow phase velocity of nystagmus after hot (44°C) and cold (30°C) caloric stimulation in either ear of <9° s–1; or 3) in both ears <15° s–1. After irrigating the ear with ice water, nystagmus was recorded in the face-up and face-down positions. The result of the test was classified as a response (nystagmus beats away from the irrigated ear in the supine position and changes when in prone), a gravity-independent response (nystagmus does not change in direction in the prone position) or no response. The spontaneous and post head-shaking nystagmus, as well as the results of the head-impulse test, were also analyzed. When indicated, a rotatory chair test was performed. Results: In the 71 patients that displayed unilateral hypofunction, the ice-water test produced a normal response in 24, a gravity-independent response in 31, and no response in 14. In two of these patients a vertical gravity-independent nystagmus response was observed. Bilateral hypofunction was found in 12 patients and the results in the head-impulse test were in agreement with the results in the ice-water test.

A Comparison of Water and Air Caloric Responses and Their Ability to Distinguish Between Patients with Normal and Impaired Ears

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. 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. 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. 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.