Sudden unilateral hearing loss and vertigo following isolated cerebellar hypoperfusion without infarction due to vertebral artery dissection.

BACKGROUND: The definition of sudden sensorineural hearing loss (SSNHL) is broadly accepted as acute sensorineural hearing loss of more than 30 dB over at least three consecutive frequencies in a pure-tone audiogram (PTA). Acute audiovestibular loss is common with ischaemic stroke in the territory of the anterior inferior cerebellar artery (AICA). However, cases in which SSNHL and vertigo occur with hypoperfusion alone are very rare. We describe a patient who developed unilateral SSNHL and vertigo as initial symptoms caused by cerebellar hypoperfusion by vertebral artery (VA) dissection without the occurrence of infarction. CASE PRESENTATION: A 51-year-old man suddenly developed acute hearing loss (AHL) in his left ear and vertigo. On neurological examination, he had vibration-induced right-beating nystagmus and left-beating nystagmus after a head-shaking test. Additionally, he had apogeotropic nystagmus during head turns to either side. The head impulse test (HIT) was normal. PTA showed mild unilateral SSNHL in the left ear. Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) showed territorial perfusion deficits in the left posterior inferior cerebellar artery (PICA) and anterior inferior cerebellar artery (AICA) without infarction. Two months later, the patient had no vertigo but still had hearing impairment in his left ear. A follow-up PTA documented persistent unilateral SSNHL in the left ear. Additionally, perfusion computed tomography (CT) showed that perfusion deficits remained in the left cerebellum along the PICA and AICA territories. CONCLUSIONS: Our case highlights a case of AHL and vertigo presented by isolated cerebellar hypoperfusion without infarction. It is necessary to consider the possibility of a central cause in patients with AHL and vertigo, and it is important to confirm this possibility through brain magnetic resonance imaging (MRI), including PWI, and magnetic resonance angiography (MRA).

The video head impulse test during post-rotatory nystagmus: physiology and clinical implications.

The aim of this study was to test the effects of a sustained nystagmus on the head impulse response of the vestibulo-ocular reflex (VOR) in healthy subjects. VOR gain (slow-phase eye velocity/head velocity) was measured using video head impulse test goggles. Acting as a surrogate for a spontaneous nystagmus (SN), a post-rotatory nystagmus (PRN) was elicited after a sustained, constant-velocity rotation, and then head impulses were applied. 'Raw' VOR gain, uncorrected for PRN, in healthy subjects in response to head impulses with peak velocities in the range of 150°/s-250°/s was significantly increased (as reflected in an increase in the slope of the gain versus head velocity relationship) after inducing PRN with slow phases of nystagmus of high intensity (>30°/s) in the same but not in the opposite direction as the slow-phase response induced by the head impulses. The values of VOR gain themselves, however, remained in the normal range with slow-phase velocities of PRN < 30°/s. Finally, quick phases of PRN were suppressed during the first 20-160 ms of a head impulse; the time frame of suppression depended on the direction of PRN but not on the duration of the head impulse. Our results in normal subjects suggest that VOR gains measured using head impulses may have to be corrected for any superimposed SN when the slow-phase velocity of nystagmus is relatively high and the peak velocity of the head movements is relatively low. The suppression of quick phases during head impulses may help to improve steady fixation during rapid head movements.

VOR gain by head impulse video-oculography differentiates acute vestibular neuritis from stroke.

OBJECTIVE: Vestibular neuritis is often mimicked by stroke (pseudoneuritis). Vestibular eye movements help discriminate the two conditions. We report vestibulo-ocular reflex (VOR) gain measures in neuritis and stroke presenting acute vestibular syndrome (AVS). METHODS: Prospective cross-sectional study of AVS (acute continuous vertigo/dizziness lasting >24 h) at two academic centers. We measured horizontal head impulse test (HIT) VOR gains in 26 AVS patients using a video HIT device (ICS Impulse). All patients were assessed within 1 week of symptom onset. Diagnoses were confirmed by clinical examinations, brain magnetic resonance imaging with diffusion-weighted images, and follow-up. Brainstem and cerebellar strokes were classified by vascular territory-posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA). RESULTS: Diagnoses were vestibular neuritis (n = 16) and posterior fossa stroke (PICA, n = 7; AICA, n = 3). Mean HIT VOR gains (ipsilesional [standard error of the mean], contralesional [standard error of the mean]) were as follows: vestibular neuritis (0.52 [0.04], 0.87 [0.04]); PICA stroke (0.94 [0.04], 0.93 [0.04]); AICA stroke (0.84 [0.10], 0.74 [0.10]). VOR gains were asymmetric in neuritis (unilateral vestibulopathy) and symmetric in PICA stroke (bilaterally normal VOR), whereas gains in AICA stroke were heterogeneous (asymmetric, bilaterally low, or normal). In vestibular neuritis, borderline gains ranged from 0.62 to 0.73. Twenty patients (12 neuritis, six PICA strokes, two AICA strokes) had at least five interpretable HIT trials (for both ears), allowing an appropriate classification based on mean VOR gains per ear. Classifying AVS patients with bilateral VOR mean gains of 0.70 or more as suspected strokes yielded a total diagnostic accuracy of 90%, with stroke sensitivity of 88% and specificity of 92%. CONCLUSION: Video HIT VOR gains differ between peripheral and central causes of AVS. PICA strokes were readily separated from neuritis using gain measures, but AICA strokes were at risk of being misclassified based on VOR gain alone.

Early adaptation and compensation of clinical vestibular responses after unilateral vestibular deafferentation surgery.

OBJECTIVE: To describe vestibulo-ocular function in the immediate postoperative period after unilateral vestibular deafferentation from vestibular schwannoma resection. STUDY DESIGN: Prospective longitudinal study. SETTING: Tertiary medical center. PATIENTS: Five patients who underwent vestibular schwannoma resection via retrosigmoid approach. INTERVENTIONS: Bedside video-oculography and video head impulse testing (HIT). MAIN OUTCOME MEASURES: Static and dynamic measures of vestibulo-ocular reflex (VOR) function including spontaneous nystagmus, skew deviation, VOR gain during HIT, and presence of saccades related to HIT. RESULTS: Mean ipsilesional horizontal VOR gain decreased from 0.88 ± 0.09 preoperatively to 0.27 ± 0.20 on POD 2 (p = 0.004). Mean contralesional VOR gain declined from 0.95 ± 0.1 preoperatively to 0.79 ± 0.17 on POD 2 (p = 0.032). By POD 4, ipsilesional VOR gain remained low, whereas contralesional VOR gain returned to baseline. Initially on POD 1 to 3, compensatory saccades occurred exclusively after the head stopped moving (overt) with latency of 192.8 ± 36.1 ms; by POD 5, saccade latency decreased to 134.5 ± 23.5 ms (p = 0.026), and saccades were occurring during the head rotation. Skew deviation was present and remained abnormal through POD 5 in 3 of the 5 patients. CONCLUSION: In the postoperative period, gaze stability seems to improve from contralesional VOR gain restoration and reduced latency of compensatory saccades.

Vestibular signs of thiamine deficiency during the early phase of suspected Wernicke encephalopathy.

Non-encephalopathic presentations of CNS thiamine deficiency may be difficult to diagnose. We describe neuro-otologic findings of Wernicke syndrome in 5 patients with vestibular manifestations. Diagnosis was confirmed by low serum levels, response to replacement, and brain MRI to exclude other causes. All had bilaterally abnormal horizontal head impulse vestibulo-ocular reflex (VOR) responses and pathologic gaze-evoked nystagmus, without encephalopathy. After thiamine replacement, 4 had total resolution of vestibular and oculomotor findings. Novel findings included 2 patients whose VOR function improved within minutes of IV repletion and 1 whose recovery was documented by serial quantitative recordings. Early diagnosis of Wernicke by examining vestibular reflexes and prompt IV treatment might prevent encephalopathy and other neurologic or systemic complications of thiamine depletion.