Location of epileptic foci on interictal and immediate postictal single photon emission tomography in children with localization-related epilepsy

Abstract

Several neuroimaging techniques that supplement electrophysiologic methods of evaluating pediatric patients with localization-related epilepsies before surgery assess both structural and functional abnormalities. For example, single photon emission computed tomography (SPECT) with technetium-99m-hexamethylpropyleneamine oxime (99mTc-HMPAO) has been used to demonstrate abnormal cerebral perfusion. States of cerebral perfusion during the interictal and immediate postictal periods have been reported to correlate with epileptiform foci identified by electroencephalogram (EEG). Between January 1987 and March 1993, we studied 55 pediatric patients with intractable seizures with prolonged video EEG telemetry in the epilepsy monitoring unit, followed by computed tomography, magnetic resonance imaging, and SPECT, before surgery to determine whether SPECT studies with 99mTc-HMPAO improved the accuracy of locating the epileptic focus. Interictal SPECT was performed on all patients, and immediate postictal SPECT (within 10 minutes after seizure ended) on 17 patients monitored in the epilepsy monitoring unit. In 15 (88%) of the 17, the combination of interictal and postictal SPECT studies yielded results corresponding to the EEG abnormality, a result significantly better than that obtained from interictal studies alone: 21 (55%) of 38 (chi 2 = 5.647, P = .0175). SPECT scans showed localized abnormal perfusion in the ipsilateral temporal lobe in all six patients with mesial temporal sclerosis, but precise results were not obtained in cases of dual pathology and neuronal migration disorders. Depiction of cerebral perfusion by interictal and immediate postictal SPECT studies can lead to greater accuracy in the localization of epileptic foci.