Scalp EEG differs in temporal and extratemporal complex partial seizures

We compared scalp ictal EEG in complex partial seizures originating in extratemporal regions with seizures originating in the temporal lobe. All patients were seizure-free for 2 or more years after appropriate cortical resection confirming focus of seizure onset. The electroencephalographer reviewing seizures was blind to patient identity. Extratemporal seizures were shorter, more difficult to lateralize, and had postictal slowing less often. Confident lateralization of seizure onset could not be made in 19% of the seizures, usually because onset was diffuse or artifact obscured the seizure. When lateralization judgments were thought possible, lateralization errors occurred in only 3% of the seizures. Five percent of the seizures had no detectable scalp ictal changes.