Adult-onset autosomal dominant myoclonic epilepsy: Report of a family with an overlooked epileptic syndrome

SummaryObjectiveMyoclonic epilepsy is a common epileptic syndrome with high genetic contribution. We described a pedigree in which 10 individuals presented with a non-progressive, adult-onset myoclonic epilepsy.Materials and methodsThe pedigree was constructed and analyzed. Six affected members were studied with clinical grounds, mental status, neurophysiology, video-electroencephalographic (EEG), brain magnetic resonance imaging (MRI) and mutational analysis of GABRA1 (GABRA1A, which endoces the α1 subunit of the γ-aminobutyric acid receptor subtype A). Clinical and EEG data were collected from six unaffected members.ResultsAutosomal dominant hereditary was shown. The age of seizure onset was approximately 40. All the individuals had myoclonic seizures and a normal cognitive level. Bilateral symmetric jerks of the shoulders, arms or legs featured the myoclonic seizure. Ictally, the consciousness was not affected. The ictal EEG demonstrated bilateral spikes-and-waves. The occurrence of myoclonic seizures was not associated with sleepiness. Rare generalized tonic-clonic seizures occurred in two individuals. No absence or accompanying involuntary movements were observed. A lower dose of valproic acid (200–500 mg/D) (clonazepam 0.5 mg/D in a patient) was required to stop the myoclonic seizures.ConclusionsThe clinical features of late adult-onset autosomal dominant myoclonic epilepsy are similar to juvenile myoclonic epilepsy (JME), which is a common generalized epileptic syndrome with a significant hereditary component. But the age of onset, rare association of other seizure patterns, and non-relation of seizure onset to sleepiness suggest that this may be a distinct familial epileptic syndrome different from recognized familial myoclonic epilepsies.