Electronystagmographic changes in patients with unilateral vestibular schwannomas in relation to tumor progression and central compensation

Vestibular function was studied in a group of 121 patients with unilateral vestibular schwannomas who were referred to University Hospital Utrecht between 1986 and 1996. Testing included the caloric test, torsion test, saccade test, smooth pursuit test and the registration of spontaneous nystagmus. Each patient’s symptoms were taken from a chart review. The size of the tumor was expressed as the maximum extrameatal diameter in the axial plane parallel to the petrous ridge as seen in magnetic resonance imaging or computed tomography. Large tumors were significantly more often accompanied by a more severe paresis on caloric testing, a smaller gain on torsion testing, spontaneous nystagmus, an abnormal saccade test and an abnormal smooth pursuit test. The presence of spontaneous nystagmus was significantly more frequently combined with an abnormal smooth pursuit and saccade test. There was a significant correlation between the slow component’s velocity of the spontaneous nystagmus and the size and progression of tumor. However, a specific relation between tumor size and central vestibular compensation could not be demonstrated.