Epilepsy, juvenile myoclonic: A form of epilepsy that occurs in young people, most commonly in the teenage years. It is characterized by jerking (myoclonic) movements of the arms and upper torso, without loss of consciousness. Seizures are most likely to occur when a person is awakening from sleep. Many children with this disorder are sensitive to light (photosensitive) and may have myoclonic jerks or seizures when exposed to bright light. Diagnosis is made through observation and EEG. During a myoclonic seizure, polyspike-wave discharges occur over a normal EEG background. Juvenile myoclonic epilepsy appears to be an inheritable genetic disorder, with the gene located on chromosome 6. Treatment is with antiseizure medications.