Vestibular investigations in acoustic neuroma

Forty-eight patients with surgically proven acoustic neuroma were examined preoperatively with a comprehensive battery of vestibular tests. In 87% of the patients, reduced caloric responses were measured on the side of the lesion. In 60% of the patients a non-responsive labyrinth was found. Spontaneous nystagmus was observed in 29% of the patients. A significant correlation with the size of the tumour was found in the occurrence of abnormal saccades in the calibration test, pathological smooth pursuit movements and the occurrence of gaze nystagmus, respectively. There was no correlation between the magnitude of the caloric response reduction and the mean hearing loss, which suggests that the hearing loss and the vestibular function loss do not occur synchronously. This study shows that in most cases of acoustic neuroma, the peripheral part of the vestibular system is severely disturbed. Abnormalities in the central and peripheral part of the vestibular system are more easily recognized with increasing tumour size. We conclude that a complete battery of vestibular tests is essential in combination with audiometric, neurologic and radiologic analysis for the early clinical diagnosis of acoustic neuroma.