Objective: The purpose of this report is to describe clinical pattern, EEG, outcome and differential diagnosis in severe myoclonic epilepsy in infancy (SMEI).
Material and methods: We report 13 cases initially diagnosed of SMEI and selected according to the following criteria: first seizure between 1 and 12 months of life, frequent seizures resistant to antiepileptic drugs, no previous personal history of disease, normal psychomotor development before the first seizure and normal EEG, CT scanning and laboratory analyses at the beginning. CT and/or MRI were performed in 13 cases, arteriography in 2 patients, MR spectroscopic imaging in 1 child and SPECT in 3 cases. Quantification of enzymatic activities of the mitochondrial respiratory chain was made in 5 patients.
Results: Only 8 cases were finally diagnosed of SMEI according to ILAE definition. In two cases, seizures were finally controlled with antiepileptic treatment and EEG abnormalities disappeared. Three patients showed other findings: mesiotemporal sclerosis, angiitis diffusely involving CNS and mitochondrial cytopathy with deficiency of the complex IV.
Conclusions: Although diagnosis of SMEI, based on clinical manifestations, is suspected in most cases from the first year of life, final diagnosis should not be confirmed until steady state, when polymorphous seizures occur. Even then, differential diagnosis should be made with other disorders. Perhaps, further studies should be performed in order to identify and eliminate another etiology.