1

Introduction

The acute vestibular syndrome is a single, prolonged episode of vertigo of acute onset (over seconds to hours) lasting days to weeks, accompanied by nystagmus, postural imbalance, head motion intolerance and nausea and/or vomiting . The most common causes of acute vestibular syndrome are vestibular neuritis and ischemic stroke in the brainstem or cerebellum . Although dizziness and vertigo are common symptoms of multiple sclerosis , either as initial manifestations or during the course of the disease, acute demyelination is an infrequent cause of acute vestibular syndrome .

The HINTS bedside examination (test for nystagmus, head impulse test and test for skew deviation) has been established as an excellent tool for the initial differential diagnosis of acute vestibular syndrome . The examination of the efferent auditory system with the suppression of transient evoked otoacoustic emissions (TEOAEs) as a part of an audiological testing battery appears to have a role in the diagnosis of multiple sclerosis and site-of-lesion diagnostics . A case of acute vestibular syndrome caused by acute demyelination is presented with the objective of highlighting the value of the clinical information provided by neuro-otological investigation.

2

Case report

A 34-year old woman was referred to our department complaining of dizziness and imbalance of abrupt onset lasting for 7 days, accompanied by head motion intolerance and mild nausea. She also complained of mild numbness on her right cheek, diminished gustatory sensation on the right side of her tongue, mild photophobia and intolerance to loud noises. She did not report of any hearing loss. The patient reported of two brief episodes of vertigo 3 years previously, for which she did not seek medical advice and therefore was not investigated. Her medical and family history was otherwise unremarkable.

The HINTS bedside examination for differential diagnosis of acute vestibular syndrome was performed upon presentation. Spontaneous, unidirectional, left-beating, horizontal–torsional nystagmus of 2nd grade (primary and left gaze) was observed with Frenzel glasses. The head impulse test was negative, indicating a central cause, and no skew deviation was noticed. Balance testing revealed severe gait ataxia. Normal pure-tone audiometry and transient evoked otoacoustic emissions (TEOAEs) along with diminished suppression of the TEOAEs on the right side ( Figs. 1 and 2 ), acoustic reflex decay on left contralateral testing and abnormal auditory brainstem responses (ABRs), provided evidence of a retrolabyrinthine lesion on the right side. Neurological examination showed vivid patellar tendon reflexes predominantly on the left and diminished cutaneous abdominal reflexes on the right. Visual evoked potentials (VEP) and fundoscopy were normal bilaterally. The rest of the neurological examination was unremarkable.

Left ear TEOAEs without and with contralateral noise. Total response difference, indicating suppression, appears within normal limits (1.7 dB SPL) revealing a functional medial olivocochlear reflex.

Right ear TEOAEs without and with contralateral noise. Total response difference, indicating suppression, is diminished (0.1 dB SPL).

Magnetic resonance imaging (MRI) revealed a high intensity (T2, flair) linear lesion in the lateral tegmentum of the pontomedullary junction, corresponding topographically to the intra-axial course of the fibers of the 8th cranial nerve ( Fig. 3 ). The lesion showed enhancement after gadolinium administration. Two small high-intensity non-enhancing periventricular lesions were also identified.

Linear demyelinating lesion in the lateral tegmentum of the pontomedullary junction on a T2 weighted image.

Cerebrospinal fluid (CSF) analysis was negative for recent infection with herpes simplex virus 1 and 2, Epstein–Barr virus, cytomegalovirus, varicella-zoster virus and Borrelia burgdoferi (Lyme disease). Immunofixation displayed oligoclonal bands, suggestive of intrathecal IgG synthesis.

With a diagnosis of clinically isolated syndrome the patient was administered 1 g of methylprednisolone for 5 days with complete resolution of her symptoms. Four months later, on follow-up, she remains free of symptoms and without new lesions on MRI. Nevertheless, suppression of the TEOAEs remains diminished.