Vestibular signs and symptoms of volumetric abnormalities of the vestibular aqueduct.

OBJECTIVE

The objective of this study was to identify a pattern of signs, symptoms and neuroradiological findings which would assist investigation of vestibular function (especially otolith function) in a group of adult patients with anatomical alterations of the endolymphatic aqueduct and sac.

METHODS

Fifteen subjects affected by volumetric abnormalities of the vestibular aqueduct were selected from a cohort of patients referred to a tertiary referral neurotological centre between 1 January 2004 and 30 June 2006. All patients underwent accurate clinical history-taking and were evaluated using a standardised set of bedside and instrumental neurotological tests (i.e. audiometry, auditory brainstem response and vestibular evoked myogenic potentials). After these tests, each patient underwent computed tomography and magnetic resonance imaging in order to accurately evaluate the middle ear, labyrinthine capsule and internal auditory canals. These evaluations confirmed clinical suspicion of volumetric abnormalities of the vestibular aqueduct and endolymphatic sac.

RESULTS

All the patients with a defined volumetric alteration in the region of the vestibular aqueduct and endolympatic sac reported a typical pattern of symptoms and signs. The most obvious and frequent symptoms in these patients were migraine-related vertigo (using the Neuhauser criteria, 10 of 15, 66.6 per cent), 'motion sickness' (12 of 15, 80 per cent), oscillopsia (nine of 15, 60 per cent) and dizziness (14 of 15, 93.3 per cent). Clinical examination results for the selected patients allowed some useful speculative conclusions. During neurotological evaluation, two instrumental methodologies were especially useful diagnostically: vestibular evoked myogenic potentials of the neck, and the mastoid vibration test at 100 Hz.

CONCLUSIONS

Dysfunction of the vestibular aqueduct is suggested by symptomatology characterised by: migraine-related vertigo, unstable or recurring oscillopsia, lowering of the vestibular evoked myogenic potential threshold, hypoacusis, anamnestic report of motion sickness, and nystagmus induced by mastoid vibration and head-shaking. Computed tomography and magnetic resonance imaging are needed in order to confirm clinical suspicions.