Hereditary essential myoclonus

A Scandinavian family whose members have suffered from hereditary essential myoclonus for five generations are presented. Three patients showed a uniform clinical picture with myoclonic jerks located in the upper trunk, the neck and proximal parts of the upper extremities without any other symptom or sign of CNS-dysfunction. The laboratory findings including EEG and somatosensory evoked potentials (SEP) were normal. Diagnostic criteria are discussed. Treatment was relatively ineffective.