EEG FINDINGS IN FRONTAL-LOBE EPILEPSIES

As a group, epilepsies of frontal lobe origin are thought to be poorly localized using surface EEG recordings. This finding may depend on th e specific areas of frontal lobe from which the seizures originate or the pathologic substrate. We reviewed the presurgical surface EEGs of patients with frontal lobe epilepsy who underwent epilepsy surgery. Th e specific area of the frontal lobe where seizures originated was dete rmined by 1) intracranial ictal EEG recordings, or 2) the presence of a structural lesion, identified by imaging studies in patients who ach ieved complete seizure control following surgery. We differentiated pa tients whose seizures began in the dorsolateral frontal convexity from those whose seizures began in the medial frontal region, and we corre lated EEG findings in the interictal, postictal, and ictal states with seizure semiology, pathologic substrate, and surgical outcome, Four o f nine patients had seizures originating in the dorsolateral frontal c onvexity and five had medial frontal onset seizures. Patients whose se izures originated from the dorsolateral convexity had focal interictal epileptiform abnormalities that localized to the region of seizure on set. Patients whose seizures began in the medial frontal region had ei ther no interictal epileptiform abnormality or had multifocal epilepti form discharges. Patients whose seizures began in the dorsolateral con vexity showed focal electrographic seizure activity that was localizin g. This rhythmic fast activity did not appear to be substrate-specific . Patients whose seizure onset localized to the medial frontal region did not show focal electrographic seizure at clinical onset. We conclu de that the scalp EEG recordings of frontal lobe epilepsies contain fe atures that enable differentiation of seizures originating from two di fferent regions of the frontal lobe.