Acquired pendular oscillation after brain-stem hemorrhage.

Six patients who manifested acquired pendular oscillation (APO) after brain-stem hemorrhage were examined with electro-oculograph. The characteristics of APO in these 6 cases were compatible with those reported in the literature as the syndrome of so-called 'rhythmic palato-ocular myoclonus'. The characteristics of APO of our cases did not differ by the presence or absence or rhythmic involuntary oscillation of the palate. In comparison with APO with multiple sclerosis (MS), our cases had slower frequency, and their amplitudes were not stable like APO with MS. Moreover, they did not disappear by lid-closure like APO with MS. Although it has been believed that the APO will continue for life, we have met with some cases which are abating gradually. It was considered that APO might be attributed to the injury of the eye position integrator that is under the influence of the rhythm generator around the reticular formation. It was found that vertical pendular oscillation (VPO) existed in 3 cases out of 6. It was concluded that the impairment of the bilateral PPRF was closely associated with the appearance of the VPO.