Post Cochlear Implantation Vertigo: Ictal Nystagmus and Audiovestibular Test Characteristics

OBJECTIVE

To investigate ictal nystagmus and audiovestibular characteristics in episodic spontaneous vertigo after cochlear implantation (CI).

STUDY DESIGN

Retrospective and prospective case series.

PATIENTS

Twenty-one CI patients with episodic spontaneous vertigo after implantation were recruited.

INTERVENTIONS

Patient-initiated home video-oculography recordings were performed during one or more attacks of vertigo, using miniature portable home video-glasses. To assess canal and otolith function, video head-impulse tests (vHITs) and vestibular-evoked myogenic potential tests were conducted.

MAIN OUTCOME MEASURES

Nystagmus slow-phase velocities (SPVs), the presence of horizontal direction-changing nystagmus, and post-CI audiovestibular tests.

RESULTS

Main final diagnoses were post-CI secondary endolymphatic hydrops (48%) and exacerbation of existing Ménière's disease (29%). Symptomatic patients demonstrated high-velocity horizontal ictal-nystagmus (SPV, 44.2°/s and 68.2°/s in post-CI secondary endolymphatic hydrop and Ménière's disease). Direction-changing nystagmus was observed in 80 and 75%. Two were diagnosed with presumed autoimmune inner ear disease (SPV, 6.6°/s and 172.9°/s). One patient was diagnosed with probable vestibular migraine (15.1°/s).VHIT gains were 0.80 ± 0.20 (lateral), 0.70 ± 0.17 (anterior), and 0.62 ± 0.27 (posterior) in the implanted ear, with abnormal values in 33, 35, and 35% of each canal. Bone-conducted cervical and ocular vestibular-evoked myogenic potentials were asymmetric in 52 and 29% of patients (all lateralized to the implanted ear) with mean asymmetry ratios of 51.2 and 35.7%. Reversible reduction in vHIT gain was recorded in three acutely symptomatic patients.

CONCLUSION

High-velocity, direction-changing nystagmus time-locked with vertigo attacks may be observed in post-CI implant vertigo and may indicate endolymphatic hydrops. Fluctuating vHIT gain may be an additional marker of a recurrent peripheral vestibulopathy.

Subjective visual horizontal correlates better with ocular than with cervical vestibular evoked myogenic potentials

OBJECTIVE

To examine the relationship between widely used otolith function tests: the Subjective Visual Horizontal (SVH) and Vestibular Evoked Myogenic Potentials (VEMP).

METHODS

A retrospective analysis was performed on 301 patients who underwent SVH, ocular and cervical VEMP (oVEMP and cVEMP) tests on the same day. Correlations between the mean SVH tilt and amplitude asymmetry ratios for bone-conducted (BC) oVEMP and air-conducted (AC) cVEMP were examined. Diagnoses included vestibular neuritis, stroke, vestibular migraine, Meniere's disease, sudden sensorineural hearing loss (SSNHL) and vestibular schwannoma.

RESULTS

SVH results were concordant with the oVEMP in 64% of cases and the cVEMP in 51%. Across all patients, SVH demonstrated a significant moderate correlation with BC oVEMP amplitude asymmetry ratios (r = 0.55, p < 0.001) and a weak correlation with AC cVEMP amplitude asymmetry ratios (r = 0.35, p < 0.001). A stronger correlation between SVH and oVEMPs was observed in patients with vestibular neuritis (r = 0.67, p < 0.001) and SSNHL (r = 0.76, p = 0.001).

CONCLUSIONS

SVH correlates better with oVEMP than cVEMP symmetry.

SIGNIFICANCE

This finding reinforces the hypothesis of a common utricular origin for both SVH and oVEMPs which is distinct from the saccular origin of cVEMPs.

Impact of Cochlear Implantation on Canal and Otolith Function

OBJECTIVE

To quantify the impact of cochlear implantation (CI) on all five vestibular end-organs and on subjective ratings of post-CI dizziness.

METHODS

Seventy-two patients undergoing unilateral CI were recruited for the study. All participants completed pre- and post-CI three-dimensional video head-impulse tests (3D vHITs) to assess semicircular-canal (SC) function, air- and bone-conducted (AC and BC) cervical and ocular vestibular-evoked myogenic potentials (cVEMPs and oVEMPs) to assess otolith-function and the dizziness handicap inventory (DHI) to measure self-perceived disability.

RESULTS

Nineteen percent of patients reported new or worsened dizziness postsurgery. Post-CI abnormalities (new lesions and significant deteriorations) were seen in the AC cVEMP (48%), AC oVEMP (34%), BC cVEMP (10%), and BC oVEMP (7%); and lateral (L) (17%), posterior (P) (10%), and anterior (A) (13%) SC vHITs. CI surgery was more likely to affect the AC cVEMP compared with the other tests (χ2 test, p < 0.05). Fifty percent of patients reported no dizziness pre- and postsurgery. In the implanted ear, normal pre-CI vHIT gain was preserved in lateral semicircular canal (LSC) (69%), anterior semicircular canal (ASC) (74%), and posterior semicircular canal (PSC) (67%), and normal reflex amplitudes were found in AC cVEMP (25%), AC oVEMP (20%), BC cVEMP (59%), and BC oVEMP (74%). Statistically significant decreases were observed in LSC vHIT gain, AC cVEMP amplitude, and AC oVEMP amplitude postsurgery (p < 0.05). There was a significant moderate positive correlation between change in DHI scores and the summed vestibular deficit postsurgery (r(51) = 0.38, p < 0.05).

CONCLUSION

CI can impact tests that assess all five vestibular end-organs and subjective ratings of dizziness. These results support pre and post-surgical vestibular testing and assist preoperative counseling and candidate selection.

Bone-Conducted oVEMP Latency Delays Assist in the Differential Diagnosis of Large Air-Conducted oVEMP Amplitudes

Background: A sensitive test for Superior Semicircular Canal Dehiscence (SCD) is the air-conducted, ocular vestibular evoked myogenic potential (AC oVEMP). However, not all patients with large AC oVEMPs have SCD. This retrospective study sought to identify alternate diagnoses also producing enlarged AC oVEMPs and investigated bone-conducted (BC) oVEMP outcome measures that would help differentiate between these, and cases of SCD.

Methods: We reviewed the clinical records and BC oVEMP results of 65 patients (86 ears) presenting with dizziness or balance problems who underwent CT imaging to investigate enlarged 105 dB nHL click AC oVEMP amplitudes. All patients were tested with BC oVEMPs using two different stimuli (1 ms square-wave pulse and 8 ms 125 Hz sine wave). Logistic regression and odds ratios were used to determine the efficacy of BC oVEMP amplitudes and latencies in differentiating between enlarged AC oVEMP amplitudes due to dehiscence from those with an alternate diagnosis.

Results: Fifty-three ears (61.6%) with enlarged AC oVEMP amplitudes were identified as having frank dehiscence on imaging; 33 (38.4%) had alternate diagnoses that included thinning of the bone covering (near dehiscence, n = 13), vestibular migraine (n = 12 ears of 10 patients), enlarged vestibular aqueduct syndrome (n = 2) and other causes of recurrent episodic vertigo (n = 6). BC oVEMP amplitudes of dehiscent and non-dehiscent ears were not significantly different (p > 0.05); distributions of both groups overlapped with the range of healthy controls. There were significant differences in BC oVEMP latencies between dehiscent and non-dehiscent ears for both stimuli (p < 0.001). A prolonged n1 125 Hz latency (>11.5 ms) was the best predictor of dehiscence (odd ratio = 27.8; 95% CI:7.0-111.4); abnormal n1 latencies were identified in 79.2% of ears with dehiscence compared with 9.1% of ears without dehiscence.

Conclusions: A two-step protocol of click AC oVEMP amplitudes and 125 Hz BC oVEMP latency measures optimizes the specificity of VEMP testing in SCD.

021 Profiles of benign positional vertigo tested on the epley omniax chair

Introduction

Benign positional vertigo (BPV) has a characteristic pattern of nystagmus specific to the affected semicircular canal and the underlying mechanism of canalithiasis (where otoconia float freely) or cupulolithiasis (where otoconia are adherent to the cupula).

Methods

We analysed the nystagmus slow-phase velocity (SPV) profiles of 100 subjects with posterior-canalithiasis, 30 with lateral-canalithiasis, 10 with lateral-cupulolithiasis and 3 with anterior-canalithiasis. Subjects were examined on the Epley Omniax Rotator, a mechanical chair with real-time video-oculography. Video data was analysed using custom-made LabVIEW software. Nystagmus onset, duration, peak-velocity, peak-latency and time taken for the peak-velocity to halve (t50), were measured.

Results

In posterior-canalithiasis, nystagmus occurred within 14.2 seconds of positioning and lasted 2.5–34.5 seconds. The median vertical peak-SPV was 37.3°/s. The median peak-latency was 2.9 seconds and the median t50 was 3.4 seconds. In lateral-canalithiasis, nystagmus onset was mostly immediate. With the affected ear down, the median peak-SPV was 52.2°/s and the median peak-latency was 3.6 seconds; the t50 was 7 seconds (median) and the paroxysms lasted 9.9–48.5 seconds. In lateral-cupulolithiasis, nystagmus onset was instantaneous. With the unaffected ear down, the median peak-SPV was 69.6°/s. The peak-latency (median 18.6 s) and t50 (median 34.5 s) were significantly prolonged compared to canalithiasis. For anterior-canalithiasis, the onset was 0–2.9 seconds, the peak-latency was 3–5.4 seconds, the t50 was 6.4–10.5 seconds and the duration was 13.4–23.1 seconds.

Conclusions

Canalithiasis and cupulolithiasis produce distinct SPV profiles, which enable their identification and the separation of BPV from other causes of positional nystagmus.