Epilepsy with myoclonic-astatic crisis is a rare form of epilepsy beginning between the second and fifth year of life. The prevalence is unknown. Boys are two times more likely to be affected than girls. Psychomotor development is usually normal before onset of the epilepsy. The disease initially manifests as tonic-clonic seizures. In some cases, multiple seizures may occur within a short space of time, even within the same day. Electroencephalogram (EEG) shows generalised spike waves. Myoclonic-astatic seizures begin several weeks later. These seizures are characterised by a sudden loss of muscular tonus associated with forward or backward propulsion that may result in injury to the face and head if the patient falls. Absence seizures are less common. The cause of the syndrome is unknown. However, increased incidence has been observed in families but the mode of transmission remains unclear and no mutations have been detected in genes known to be associated with channelopathies, except in a few reported cases. Although epilepsy with myoclonic-astatic crisis and Lennox-Gastaut syndrome (see this term) have often been confused, these two types of epilepsy are distinct entities. As the quality of the antiepileptic treatment is of vital importance from the beginning of the disease, it is essential to avoid delays in starting the treatment and administration of inappropriate medication. In one third of patients, the epilepsy is refractory to treatment leading to worsening of the seizures and progression to a myoclonic state with drowsiness and erratic jerks affecting the hands and region around the mouth, associated with the occurrence of tonic seizures particularly during sleep. In forms with an unfavourable evolution, the myoclonic state resolves after several months. Sequelae include cognitive difficulties and major motor anomalies or lead to dyspraxia, slowness and dysarthria, as well as tonic seizures during sleep.
Last update: October 2006