Abstracts

To characterize the various electroencephalographic (EEG) patterns encountered in myoclonic-astatic epilepsy (MAE) of early childhood. MAE has a heterogenous clinical presentation, with onset of myoclonic and myoclonic-astatic seizures in a previously developmentally normal child. The presence of focal epileptiform discharges is one of the exclusion criteria in the modified ILAE classification. The generalized 2-3 Hz spike- or polyspike-wave discharges are the accepted EEG findings.
Three patients, 3-7 years of age, with clinical presentation consistent with MAE were monitored in the Pediatric Epilepsy Monitoring Unit (PEMU) at the University of Michigan. All patients had normal development prior to the onset of seizures, which occurred between 2 and 4 years of age. All three had a history of infrequent generalized tonic clonic seizures. Two of the patients had a history of febrile seizures. Two patients had frequent episodes consistent with myoclonic and/or myoclonic-atonic seizures. The third patient had a known history of absence seizures, however myoclonus or atonic seizures were not described prior to the EEG monitoring.
During the video EEG monitoring study, two recordings revealed normal background activity, however a third one was remarkable for high amplitude 3-5 Hz slow background. All three EEG studies were notable for the presence of high amplitude, irregular 2-2.5 Hz spike- and polyspike-wave EEG discharges. In only one patient with recorded myoclonic and myoclonic-atonic sz, topographic mapping revealed an oblique dipole with maximum frontal negativity (of higher amplitude) and posterior positivity, and with shifting left/right emphasis. The patient who reportedly had only absence seizures, also had myoclonic seizures identified during this monitoring study. The other two patients had numerous seizures of myoclonic and atonic semiology. The EEG correlate was similar for all seizure types recorded and consisted of bursts of generalized 2-3 Hz spike- and polyspike-wave discharges.
The clinical features and the ictal EEG findings in all three cases presented are consistent with the accepted definition of MAE. The only unique feature is the presence of the oblique dipole in one of the studies. We propose that the presence of interictal focal epileptiform discharges in the EEG of patients with findings otherwise typical of MAE should not be an exclusion criteria, as currently stated in the modified ILAE criteria.