Myoclonic status in non-progressive encephalopathies or Dalla Bernardina syndrome

Abstract

We present an update of a series of patients with myoclonic status in non-progressive encephalopaties (MSNPE) describing the electroclinical features and outcome. Between February 1, 1990 and June 30, 2011, 41 patients who met diagnostic criteria of MSNPE were seen at our department and followed up to the present time. Three main subgroups were identified. The first subgroup of 27 patients presented with myoclonic absences and rhythmic myoclonias followed by a brief silent period associated with subcontinuous delta-theta activity involving the central areas and rhythmic delta waves with superimposed spikes mainly involving the parietooccipital regions and often activated by eye closure. This pattern was found in all children with a genetic etiology. The second subgroup included seven patients showing a pattern characterized by inhibitory phenomena associated with a dystonic component and sudden irregular rapid lightning-like jerks. The electroencephalography showed subcontinuous multifocal slow spike-waves, predominating in frontocentral regions. These patients had a cortical malformation or the etiology was unknown. The third subgroup included seven children who initially suffered from myoclonic absences. The status was initially characterized by subcontinuous generalized spike-wave-type paroxysms related to rhythmic myoclonia of face and limbs. After 1 to 3 wk, the electroencephalography showed sharp theta waves with very slow pseudorhythmic continuous spikes in the central regions and vertex. The etiology was found to be perinatal anoxic injury. MSNPE is a well-defined epileptic syndrome in the group of epileptic encephalopathy secondary to different, but mostly genetic, etiologies.