Abstracts

The third rhythm is a temporal alpha range rhythm, which may have a relationship to wicket spikes. This may occasionally contribute to misdiagnosis of epilepsy. We have encountered seven patients who received the erroneous diagnosis of epilepsy based on misinterpretation of the third rhythm. We reviewed medical records and EEG data in seven patient misdiagnosed with epilepsy because of a third rhythm. Four patients received EEG-video monitoring, three with sphenoidal electrodes. Three others had only standard EEG. Four patients with no skull defect had video EEG monitoring, three with sphenoidal electrodes. Three with skull defects had only standard EEG. The third rhythm consisted of rhythmic alpha range activity recorded from the sphenoidal electrode or the anterior-mid temporal region. It was at times particularly sharp in the sphenoidal electrode. The third rhythm disappeared with deepening sleep. Non-epileptic psychogenic seizures were recorded in three patients. These patients were discharged on no antiepileptic drugs (AEDs), and stopped having attacks. One other without video-EEG was taken off AEDs, with no seizures. The third rhythm can have a sharp appearance in some patients, particularly on sphenoidal recordings, and can be easily misdiagnosed. A sharp third rhythm should be added to the list of [ldquo]benign variants[rdquo] misdiagnosed as epileptiform.[figure1]