Vestibular neuronitis: Inflammation of the vestibular nerve, the nerve running to the vestibule. (The vestibule is in the inner ear. Like an internal carpenter's level, it and the semicircular canals work with the brain to sense, maintain, and regain balance and a sense of where the body and its parts are positioned in space.)
Vestibular neuronitis is a paroxysmal attack of severe vertigo (dizziness) which is not accompanied by deafness or tinnitus (ringing in the ear). It affects young to middle-aged adults and often follows a nonspecific upper respiratory infection.