The clinical and EEG features and reasons for frequent misdiagnosis of juvenile myoclonic epilepsy are reviewed by the Epilepsy Research Group, Institute of Neurology, National Hospital, and St Thomas’ Hospital, London, England. The triad of absence seizures, myoclonic jerks, and GTCSs shows a characteristic age-related onset. Absence seizures begin between 5 and 16 years, myoclonic jerks follow about 4 years later, usually around age 15 years, and GTCSs appear within a few months after the myoclonic jerks. Myoclonic jerks and GTCSs occur mainly on awakening. Apart from tremor, the neurologic exam is normal. Photosensitivity is present in 50% of patients, and seizures are precipitated by sleep deprivation, fatigue, alcohol, anxiety, and hyperventilation. Treatment with valproic acid is usually effective, and may be supplemented with clonazepam at bedtime if necessary. Lifelong anticonvulsant treatment is required, and withdrawal of medication may result in status epilepticus. 
COMMENT. A high index of suspicion for JME is indicated in young patients with early-morning seizures, especially those poorly controlled with carbamazepine or associated with sleep deprivation or alcohol consumption.
Diagnosis of JME was delayed by a mean of 14 years in 15 patients identified among 180 referrals to a new epilepsy clinic at St Thomas’ Hospital, London, a prevalence of 8.3%. At least 11 had been examined previously by a neurologist, and 7 had received inappropriate anticonvulsants.