Myoclonic status in nonprogressive encephalopathies: study of 29 cases.
OBJECTIVE
Myoclonic status in nonprogressive encephalopaties (MSNE) is characterized by recurrence of long-lasting myoclonic status appearing in infants and young children with nonprogressive encephalopathy. Here, we describe the electroclinical features and evolution of MSNE.


METHODS
Between February 1, 1990 and July 31, 2005, 29 patients who met diagnostic criteria of MSNE were enrolled in the study at our department and have been followed up to the present time.


RESULTS
Three main subgroups could be identified. The first subgroup of 18 patients presented myoclonic absences and rhythmic myoclonias. These were followed by a brief silent period related to a 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. It was found in all children with a genetic etiology. The second subgroup included five patients showing a pattern characterized by inhibitory phenomena associated with a dystonic component and sudden irregular rapid lightning-like jerks. The EEG showed subcontinuous multifocal slow spike-waves, predominating in frontocentral regions. These patients are affected by a cortical malformation or the etiology is unknown. The third subgroup included six 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 1-3 weeks, the EEG 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.


CONCLUSIONS
MSNE should be considered as a new epileptic syndrome in the group of epileptic encephalopathy.
Caraballo
Roberto Horacio
RH
Department of Neurology, Hospital de Pediatría Prof Dr. Juan P. Garrahan, Buenos Aires, Argentina. rhcaraballo@arnet.com.ar
Cersósimo
Ricardo Oscar
RO
Espeche
Alberto
A
Arroyo
Hugo Antonio
HA
Fejerman
Natalio
N
D000293:Adolescent; D002540:Cerebral Cortex / Q000002:abnormalities / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003700:Delta Rhythm; D004569:Electroencephalography / Q000706:statistics & numerical data*; D004831:Epilepsies, Myoclonic / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology; D004832:Epilepsy, Absence / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D013577:Syndrome; D013826:Theta Rhythm