Factors contributing to the misdiagnosis of juvenile myoclonic epilepsy (JME) in an epilepsy clinic have been examined in 70 patients at the Division of Neurology, King Khalid University Hospital, Riyadh, Saudi Arabia. More than 90% were undiagnosed on referral and 33% were not recognized initially in the epilepsy clinic. The delay in diagnosis was 8 years from onset and 17 months from the first evaluation in the clinic. Factors responsible for the delayed diagnosis include the following: myoclonic jerks rarely reported by patients; generalized tonic-clonic seizures may be nocturnal without circadian relation to awakening from sleep; unilateral jerks may suggest simple partial seizures; absence seizures may antedate jerks and GTCS seizures by 4.5 years and are frequently unrecognized. The EEG was significant in confirming the diagnosis in 63% of patients. Valproate is considered the treatment of choice and clonazepam is used as an adjunctive treatment. 
COMMENT. Failure to recognize JME may result in improper choice of anticonvulsant therapy, resultant status epilepticus, and failure to provide appropriate genetic counseling. This study reemphasizes the atypical history in some cases and the frequency of occurrence of absence seizures as the initial manifestation.