Abstract

Background
and Objectives: Acoustic neuroma (AN) is commonly encountered in the cerebello-pontine angle (CPA) and AN arises principally from the vestibular division of the nerve, which can show not only hearing disturbance but also various vestibular symptoms and laboratory findings by affecting central and peripheral vestibular system. Vestibular testing is reported not to be a useful screening test for AN, but can be helpful in defining whether the tumor arises from the superior or inferior division and identifying the cause of dizziness or vertigo. Materials and Method: We are presenting four patients with CPA tumors accompanied by various abnormal findings of vestibular function tests including head-shaking nystagmus, vibration-induced nystagmus, hyperventilation- induced nystagmus and vestibular evoked myogenic potential and subjective visual vertical, which can enable us to understand the pathomechanism of the abnormal results.
Results
All patients presented hearing loss and mild dizziness. Caloric test, head thrust test and vibration-induced nystagmus was helpful in localizing the disease, but head-shaking nystagmus and hyperventilation-induced nystagmus was less helpful. Otolith tests did not always show abnormal results.
Conclusion
We should consider abnormal results of the vestibular function tests in a whole to estimate the status of vestibular compensation in patients with CPA tumors. Key Words : Nystagmus, Subjective visual vertical, Acoustic neuroma

• Keywords: Nystagmus;Subjective visual vertical;Acoustic neuroma;