REFLEX MYOCLONUS IN OLIVOPONTOCEREBELLAR ATROPHY

The presence of reflex myoclonus in response to touching and pinpricki ng the wrist or stretching the fingers and to photic stimulation was a ssessed in 24 patients with a presumed diagnosis of olivopontocerebell ar atrophy (OPCA) and in 30 age matched control subjects. Reflex myocl onus to somaesthetic stimulation was found in 23 patients and in none of the controls. Photic myoclonus was present in 12 patients and in no ne of the controls. Electrophysiological study of the reflex myoclonus showed enhanced (> 10 mu V) somatosensory evoked potentials and an as sociated reflex electromyographic discharge (C-wave) in 15 patients. T hese findings indicate that reflex myoclonus is common in OPCA and pro bably of cortical origin.