[Rhythmical involuntary movement at rest associated with olivo-ponto-cerebellar atrophy (OPCA)]

The authors analyzed rhythmical involuntary movements at rest, which appeared as complications in 12 (sporadic 11, hereditary 1) out of a total of 139 cases (sporadic 99, hereditary 40) of olivo-ponto-cerebellar atrophy. These movements tended to be seen in patients with sporadic OPCA of longer illness duration and at more advanced stages. They were distributed over the face, neck and extremities. Palatal myoclonus was observed in only one case. The movements were exacerbated by maintenance of a fixed posture, motion and mental stress, and stopped during sleep. In some cases, clonazepam, trihexyphenidyl or 1-Dopa was effective. In the surface electromyogram, rhythmical grouped discharges of 2-4 Hz were recorded only on agonist muscles or on both agonist and antagonist muscles synchronously, which is characteristic of skeletal myoclonus. However, pathological study of 3 cases with involuntary movements revealed marked putaminal degenerations as compared with 3 uncomplicated cases. This suggests that these rhythmical movements might be related to parkinsonian tremor.