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.
Keywords
Angelman syndrome - epileptic encephalopathy - myoclonic seizures - negative myoclonia
- non-progressive encephalopathy - refractory epilepsy
