This syndrome a common idiopathic generalized epilepsy syndrome, accounting for ~10% of all epilepsies. It is characterized by myoclonic with or without generalized tonic-clonic seizures in an otherwise normal individual. The EEG must show generalized spike- or polyspike-wave for the diagnosis of this syndrome. Photosensitivity is common, occurring in up to 90% of individuals.
This syndrome begins 8-40 years of age (typically 10-24 years). There is a slight female preponderance. Antecedent and birth history is normal. Development and cognition are typically normal, though specific cognitive impairments (e.g. in executive function, impulse-regulation or in attention) can be seen. Neurological examination and head size are normal. Between 5-15% of patients have previously had childhood absence epilepsy. A history of febrile seizures is seen in 5% of cases.