Presurgical evaluation of patients with epilepsy and normal MRI: role of scalp video-EEG telemetry

When considering surgery for intractable partial seizures, even with high r esolution MRI, some patients do not show structural abnormalities. The aim was to consider whether these patients were likely to proceed to surgical t reatment after scalp video-EEG telemetry. All patients undergoing presurgic al evaluation at the National Hospital for Neurology and Neurosurgery betwe en 1995 and 1997 were reviewed and 40 were identified without definite MRI abnormalities. None of 40 disclosed a well localised epileptogenic zone con cordant with other tests that would have allowed the patient to proceed dir ectly to surgery. In five of the 40, evaluation led to a hypothesis that co uld be tested by intracranial studies; three proceeded to surgery. It is su ggested that high quality MRI is performed first when surgical evaluation i s undertaken and if negative the patient carefully counselled before procee ding with any investigations, as successful resective surgery is an unlikel y outcome in such MRI negative cases.