Abstract

Acute peripheral unilateral vestibular loss of unknown etiology is also diagnosed as (cochleo)vestibular neuritis or labyrinthitis/neurolabyrinthitis depending on hearing involvement. Even though the extent of vestibular involvement can be variable, they typically affect the superior vestibular nerve territory (horizontal and anterior semicircular canal and utricle) with sparing of the inferior part (posterior semicircular canal and saccule). Selective inflammation of the superior division of the vestibular nerve or anatomical differences in the bony canals of the two divisions might explain this relative vulnerability. We report on a case of cochleovestibular neuritis which was originated from the cochlear nerve and posterior ampullary nerve territory and progressed to the whole eighth nerve territory. A 41-year-old woman visited out patient clinic for sudden onset of vertigo and right hearing loss 1 day ago. Audiometry showed 90 dB sensorineural hearing loss with 44% speech discrimination. Spontaneous nystagmus was subtle down beating with counterclockwise torsional component, which was augmented by head shaking maneuver. Caloric test, rotational test and fundus finding were normal range. VEMP response and threshold were symmetrically normal. On head thrust test using search coil, the gain was markedly decreased only in right posterior canal stimulation. After 2weeks later, vertigo was aggravated and spontaneous nystagmus was left-beating horizontal with torsional component which is typically observed in right peripheral vestibular paresis. On follow up head thrust test, gain was decreased in all three right side semicircular canal stimulation. We reported a case of atypical acute peripheral vestibulopathy, in which a branch of inferior vestibular nerve territory is isolated involved. And considering the involvement of inferior vestibular nerve territory sparing of saccular branch at initial presentation, neural lesion rather than labyrinthine lesion seems to be responsible for the development of neurotologic symptoms in this patient.