Evaluation of the vestibulo-ocular reflex using sinusoidal off-vertical axis rotation in patients with acoustic neurinoma

• Published in: Neuroscience letters 2009-10, Vol.462 (1), p.6-9
• Main Authors: Sugita-Kitajima, Akemi, Koizuka, Izumi
• Format: Article
• Language: English
• Subjects: Acoustic neurinoma; Adult; Aged; Biological and medical sciences; Darkness; Ear Neoplasms - diagnosis; Ear, Inner; Female; Fundamental and applied biological sciences. Psychology; Humans; Inferior vestibular nerve; Light; Male; Middle Aged; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Neuroma, Acoustic - diagnosis; Off-vertical axis rotation; Posture; Reflex, Vestibulo-Ocular; Rotation; Superior vestibular nerve; Vertebrates: nervous system and sense organs; Vestibular schwannoma; Vestibulo-ocular reflex
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2009.06.078

The vestibulo-ocular reflex (VOR) was studied to examine the utility of off-vertical axis rotation (OVAR) in the diagnosis of acoustic neurinoma. Subjects were sinusoidally rotated with eyes open in complete darkness at frequencies of 0.4 and 0.8 Hz with a maximum angular velocity of 60°/s at either earth-vertical axis rotation (EVAR) or OVAR. Thirteen patients with acoustic neurinomas were investigated. Results showed that VOR gain during OVAR at 0.8 Hz and in a 30° nose-up position in patients with internal auditory canal tumors was significantly less than the gain measured during EVAR. The VOR gain measured from all patients (including those with tumors extending to the cerebellopontine angle) was not significantly different when the patients were subjected to EVAR and OVAR. These observations were possibly due to superior vestibular nerve dysfunction. We concluded that certain stimulating parameters—patient's nose tilted up 30°; sinusoidal OVAR at 0.8 Hz and 60°/s maximum angular head velocity—were useful for evaluating vestibular function in patients suffering from an acoustic neurinoma located within the internal auditory canal.