Limited efficacy of levetiracetam on myoclonus of different etiologies.

Levetiracetam is a relatively new antiepileptic drug, which has been reported to have promising antimyoclonic properties, especially in posthypoxic myoclonus, progressive myoclonic epilepsy (PME) and spinal myoclonus. Eight patients with intractable myoclonus of various etiologies were given levetiracetam as add-on therapy in an open-label trial. Physician and patient self-assessments were recorded over 1 year. Symptomatic improvement occurred only with posthypoxic myoclonus, which was rapid, dramatic and sustained. All other forms of myoclonus either did not improve or worsened (1 essential myoclonus, 2 myoclonus-dystonia, 2 PME, 2 mitochondrial disease). Levetiracetam has promising but selective antimyoclonic potential, which should be the subject of further study.