Benign myoclonic epilepsy of infancy: electroclinical symptomatology and differential diagnosis from the other types of generalized epilepsy of infancy.

Benign myoclonic epilepsy in infancy (BME) is characterized by the occurrence of brief myoclonic attacks in normal infants aged 4 months to 3 years. There is no prior personal history, although in some patients 1 or 2 isolated febrile convulsions may occur prior to the onset of myoclonias. A family history of epilepsy or febrile convulsions is present in 30% of cases. Myoclonic attacks are short and mild, they involve mainly the head and upper limbs. The psychomotor development continues normally after the onset of seizures. The EEG shows a normal background activity and generalized spike-wave or polyspike-wave discharges associated with the myoclonias. These abnormalities are activated by drowsiness and during the first stages of sleep. A clinical and EEG photosensitivity is present in one-third of the patients. Myoclonias can be easily controlled by valproate monotherapy. Rare grand mal seizures can occur during adolescence, after withdrawal of drug treatment. The psychomotor evolution is good if treatment is started early. When myoclonias begin during the first year of life, the diagnoses of cryptogenic infantile spasms and of non-epileptic benign infantile myoclonus must be eliminated. In cases with a later onset, the following diagnoses can usually be easily discarded: cryptogenic Lennox-Gastaut syndrome, myoclonic-astatic epilepsy and unclassified epilepsies with the association of myoclonias and other types of seizures.