Steal phenomenon in Sturge-Weber syndrome imitating an ictal electroencephalography change in the contralateral hemisphere: report of 2 cases.

Infants with Sturge-Weber syndrome (SWS) are considered for surgery if they develop seizures and the seizures prove medically refractory. The authors report on 2 infants (15 and 19 months old) with SWS who underwent scalp video electroencephalography (EEG) and subsequent functional hemispherotomy for intractable partial motor seizures due to extensive left hemispheric angiomatosis. They presented with similar interictal and ictal EEG findings. Ictal EEG showed abrupt high-amplitude delta slow waves, without evolution on the contralateral hemisphere before the build-up of ictal EEG changes on the lesional hemisphere. The patients became seizure free after hemispherotomy. The ictal contralateral slow waves were not a sign of an ictal hemisphere and may indicate prominent ischemic changes resulting from a steal phenomenon of hemispheric angiomatosis during seizure.