Cerebellopontine angle tumors: bilateral flocculus compression as cause of associated oculomotor abnormalities.

Oculomotor abnormalities of pursuit, OKN, gaze as well as saccade are frequently found in patients with large cerebellopontine angle tumors. Evidence is presented in support of the proposition that bilateral flocculus compression is likely responsible for the majority of oculomotor abnormalities noted in these patients. An hypothesis for the genesis of Bruns' as well as bilateral gaze paretic nystagmus is put forward. Successful tumor removal implies that pursuit and optokinetic nystagmus are more sensitive than the other oculomotor functions to the compressive effects of a cerebellopontine angle mass.