Otoneurological diagnostics in posterior fossa lesions.

When investigating patients with suspicion of a posterior fossa lesion, case history and clinical examination are important. Additional information is obtained by using an otoneurological test battery consisting of electronystagmography and audiology, primarily brain stem audiometry. In the electronystagmography one should look for spontaneous, positional and gaze nystagmus and asymmetry in the caloric test. In our material of 78 patients with acoustic neuromas, spontaneous nystagmus was present in 58%, positional nystagmus in 43% gaze nystagmus in 5% and caloric asymmetry in 88%. To reveal CNS disturbances in the posterior fossa, whether due to pressure from a pontine angle tumour or a vascular loop, or caused by cerebellobrainstem infarction, bleeding or tumour, certain special tests have proved valuable: computerized sinusoidal vs. randomized rotatory and smooth pursuit tests and ocular saccade test. A visual suppression test performed in the rotatory chair makes it possible to compare suppression and pursuit at identical stimulation patterns, which adds a new diagnostic tool.