Myoclonic epilepsy in infancy: an electroclinical study and long-term follow-up of 38 patients.

PURPOSE: Myoclonic epilepsy in infancy (MEI) is characterized by brief generalized myoclonic seizures associated with generalized spike-wave paroxysms without other seizure types occurring in the first 3 years of life in developmentally normal children. In this study we analyze the electroclinical features, treatment, and outcome of 38 patients with MEI.

METHODS: A retrospective chart review was conducted in 38 patients followed at the Neurology Department of the Pediatric Hospital Juan P. Garrahan in Buenos Aires, Argentina, between 1990 and 2012.

KEY FINDINGS: A total of 24 boys and 14 girls were identified. The mean and median ages at seizure onset were 16 and 18 months, respectively (range 3-40 months). Ten patients (28.9%) had a family history of epilepsy, and six (15.8%) had a family history of febrile seizures. All patients had several daily brief and isolated myoclonic seizures during wakefulness and predominantly in the first two stages of sleep. Twelve children (31.5%) had reflex myoclonus, triggered by a tactile stimulus in 10 and additionally by noise and light in 2. The remaining two had photosensitive myoclonic jerks. The interictal electroencephalography (EEG) recordings evidenced generalized spike waves, polyspikes, and polyspike-wave paroxysms. The interictal EEG was normal in 12 patients. The abnormalities on the ictal EEG were similar to those on the interictal EEG. Most of the patients responded well to valproic acid. After a mean follow-up of 13.5 years, 24 patients (63%) were without treatment. At the last examination, 32 patients had normal neurologic and neuropsychological evaluations. Two patients (5.2%) had significant cognitive impairment (an IQ of 60 and 63, respectively) despite good seizure control. Four patients (10.4%) had significant learning impairment, two of whom also had attention deficit hyperactivity disorder.

SIGNIFICANCE: MEI is a well-defined epileptic syndrome of unknown etiology, but likely of a genetic cause. It is self-limited and pharmacosensitive mainly to valproic acid.