Epileptology of the first-seizure presentation: a clinical, electroencephalographic, and magnetic resonance imaging study of 300 consecutive patients

Background Prognosis and treatment of the first seizure depends on identification of a specific epilepsy syndrome, yet patients with first seizures are generally regarded as a homogeneous group. We studied whether it is possible to diagnose specific epilepsy syndromes promptly by use of standard clinical methods, electroencephalography (EEG) and magnetic resonance imaging (MRI). Methods 300 consecutive adults and children presented with unexplained seizures. We systematically collected clinical data from patients and witnesses, and attempted to obtain an EEG within 24 h of the seizure. Where the EEG was negative, a sleep-deprived EEG was done. MRI was done electively. Findings A generalised or partial epilepsy syndrome was clinically diagnosed in 141 (47%) patients. Subsequent analysis showed that only three of these clinical diagnoses were incorrect. Addition of the EEG data enabled us to diagnose an epilepsy syndrome in 232 (77%) patients. EEG within 24 h was more useful in diagnosis of epileptiform abnormalities than later EEG (51 vs 34%). Neuroimaging showed 38 epileptogenic lesions, including 17 tumours. There were no lesions in patients for whom generalised epilepsy was confirmed by EEG. Our final diagnoses were: generalised epilepsy (23% of patients); partial epilepsy (58%); and unclassified (19%). Interpretation An epilepsy syndrome can be diagnosed in most first-seizure patients. Ideally, an EEG should be obtained within 24 h of the seizure followed by a sleepdeprived EEG if necessary. MRI aids diagnosis and should be done for all patients except for those with idiopathic generalised epilepsies and for children with benign rolandic epilepsy.