A benign SCHWANNOMA of the eighth cranial nerve (vestibulocochlear nerve), mostly arising from the vestibular branch (vestibular nerve) during the fifth or sixth decade of life. Clinical manifestations include hearing loss; headache; vertigo; tinnitus; and facial pain. Bilateral acoustic neuromas are associated with neurofibromatosis 2. (From Adams et al., Principles of neurology, 6th ed, p673)