Sudden vertigo in a 49-year-old man

Abstract

The diffusion-weighted MRI (DWI) showed a small, subacute right middle cerebellar peduncle infarct in the territory of the anterior inferior cerebellar artery (AICA) without brainstem infarction (Fig. 1). Audiometry showed a total right hearing loss with normal hearing on the left; caloric testing showed absent responses from the right. CT angiography revealed only right vertebral artery hypoplasia. He was given anti-hypertensive treatment and aspirin. One year later he still had a total right hearing loss, positive rightward Head Impulse Test, a positive Romberg test standing on foam and absent caloric responses from the right. Sudden unilateral vestibular loss (SVL) produces a stereotyped syndrome of vertigo, vomiting, nystagmus beating away from the affected side, ipsiversive lateropulsion and ocular tilt reaction. The Head Impulse Test is invariably positive towards the affected side. Whereas the SVL syndrome invariably resolves within 1 week, the Head Impulse Test will, if the ear does not recover, remain positive forever. When the SVL is spontaneous and isolated, the cause is usually presumed to be due to herpes simplex virus infection and since the cochlea is spared, it is called ‘‘acute vestibular neuritis’’. When there is simultaneous sudden unilateral hearing loss (SHL) the cause is presumed to be herpes zoster virus infection – ‘‘herpes zoster oticus’’ or the ‘‘Ramsay Hunt syndrome’’, affecting the labyrinth as well as in the vestibulo-cochlear nerve, and such cases are called ‘‘acute viral labyrinthitis’’ or ‘‘neuro-labyrinthitis’’. However, labyrinthine infarction can also cause combined SVL+SHL, although this diagnosis is as hard to verify as that of viral labyrinthitis, since MRI of the inner ear is usually normal in both. The internal auditory artery, usually a branch of the AICA, supplies the inner ear. With AICA occlusion there can be infarction in the cerebellum or the brainstem, or both, as well as the inner ear. The hearing loss with AICA infarction is mostly cochlear and can improve in time, as can the canal paresis. A cerebellar or even brainstem component of an AICA territory infarct, evident on DWI, can be clinically asymptomatic so that the patient will present with isolated SHL+SVL and if a DWI is not requested (in time), the patient will be assumed to have viral