Functional Loss After Meningitis-Evaluation of Vestibular Function in Patients With Postmeningitic Hearing Loss

Posterior Canal Fibrosis: A Case Series

OBJECTIVE

To establish a case series where loss of magnetic resonance fluid signal intensity in the posterior semicircular canal (SCC) corresponded with a functional deficit on clinical and video head impulse testing, and most likely a result of canal fibrosis or obstruction.

PATIENTS

Three patients with an magnetic resonance imaging (MRI) showing loss of T2-weighted signal intensity in their posterior SCC corresponding to a vestibular weakness in that canal.

INTERVENTIONS

All patients underwent a comprehensive neuro-otologic examination. Vestibulo-ocular reflex was evaluated using clinical head impulse testing (cHIT) and quantified with video head impulse testing. MRI for all patients was obtained using clinical protocols for gadolinium-enhanced MRI of the internal auditory canal on 1.5 or 3 T scanners, which all included high-resolution, heavily T2-weighted imaging of the membranous labyrinth.

MAIN OUTCOME MEASURE

Correlation of MRI findings with vestibular weakness in the corresponding posterior SCC.

RESULTS

Subject 1 showed abnormal vHIT in the left lateral and left posterior SCCs. MRI showed loss of T2 signal intensity of the entire left posterior SCC as well as in the posterior limb of the superior SCC. Subject 2 showed isolated loss of function (cHIT) and low gain with catch-up saccade (vHIT) of the left posterior SCC. MRI showed loss of T2 signal intensity of the superior portion of the left posterior SCC, as well as in the posterior limb of the superior SCC. Subject 3 showed catch-up saccades of the left posterior SCC on cHIT and vHIT and loss of T2 signal intensity of the entire left posterior SCC and partial loss of bilateral lateral SCC on MRI.

CONCLUSIONS

In this case series, loss of posterior SCC function correlated with vestibular function testing and high-resolution, T2-weighted MRI findings, perhaps related to fibrosis of the posterior SCC.

Vestibular Function in Children and Adults Before and After Unilateral or Sequential Bilateral Cochlear Implantation

Background: Cochlear implantation (CI) helps patients with severe or profound sensorineural hearing loss (SNHL) restore hearing and speech abilities. However, some patients exhibit abnormal vestibular functions with symptoms such as dizziness or balance disorders, after CI. Whether age at CI and CI approach (unilateral or sequential bilateral) affect vestibular functions in users with cochlear implants remains unclear.

Objectives: To investigate the vestibular functions in children and adults before and after unilateral or sequential bilateral CI.

Materials and Methods: Thirty-seven patients with severe or profound SNHL who were candidates for a first- or second-side CI were divided into three groups: first-side CI-implanted adults (≥18 years), first-side CI-implanted children (6–17 years), and second-side CI-implanted children (6–17 years). All cases were implanted with the round window approach to minimize damage to the intra-cochlear structures. The caloric test, vestibular evoked myogenic potential (VEMP) test, video head impulse test (vHIT), Dizziness Handicap Inventory (DHI), Pediatric Vestibular Symptom Questionnaire (PVSQ), and audiometric tests were performed before and 1 month after CI.

Results: The abnormal rates of caloric test and VEMP test after CI in the first-side CI-implanted adults and children significantly increased compared with those before CI. The pre-implantation VEMP test showed significantly higher abnormal rates between first- and second-side CI-implanted children. No other significant differences of abnormal rates between first- and second-side CI-implanted children or between first-side CI-implanted adults and children were found. In second-side CI-implanted children, PVSQ scores significantly increased at day 3 post-implantation but decreased at day 30.

Conclusion: CI has a negative effect on the results of caloric and VEMP tests, but not on vHIT, indicating that the otolith and low-frequency semicircular canal (SCC) are more vulnerable to damage from CI. The alterations of vestibular functions resulting from CI surgery may be independent of age at CI and CI approach (unilateral or sequential bilateral). Long-term impacts on the vestibular function from CI surgery, as well as the chronic electrical stimulation to the cochlea, are still to be investigated.

Case Report: Filling Defect in Posterior Semicircular Canal on MRI With Balanced Steady-State Gradient-Echo Sequences After Labyrinthine Ischemia in the Common Cochlear Artery Territory as an Early Sign of Fibrosis

We describe a rare case of posterior semicircular canal (PSC) fibrosis following acute labyrinthine ischemia in the territory supplied by the common cochlear artery (CCA) and review the relevant literature. A 71-year-old man with multiple vascular risk factors presented 12 days after the onset of acute vertigo and profound left-sided hearing loss. Right-beating spontaneous nystagmus with downbeat components elicited by mastoid vibrations and headshaking was detected. The video head impulse test (vHIT) revealed an isolated hypofunction of the left PSC, whereas vestibular evoked myogenic potentials (VEMPs) showed ipsilateral saccular loss. The clinical presentation and instrumental picture were consistent with acute ischemia in the territory supplied by left CCA. Compared to previous imaging, a new MRI of the brain with 3D-FIESTA sequences highlighted a filling defect in the left PSC, consistent with fibrosis. Hearing function exhibited mild improvement after steroid therapy and hyperbaric oxygen sessions, whereas vHIT abnormalities persisted over time. To the best of our knowledge, this is the only case in the literature reporting a filling defect on MRI, consistent with semicircular canal fibrosis following acute labyrinthine ischemia. Moreover, PSC fibrosis was related with poor functional outcome. We therefore suggest using balanced steady-state gradient-echo sequences a few weeks following an acute lesion of inner ear sensors to detect signal loss within membranous labyrinth consistent with post-ischemic fibrosis. Besides addressing the underlying etiology, signal loss might also offer clues on the functional behavior of the involved sensor over time. In cases of acute loss of inner ear function, a careful bedside examination supplemented by instrumental assessments, including vHIT and VEMPs, of vestibular receptors and afferents may be completed by MRI with balanced steady-state gradient-echo sequences at a later time to confirm the diagnosis and address both etiology and functional outcome.