Effect of seizures on cerebral blood flow measured with O-15-H2O and positron emission tomography

To study quantitative alterations in regional cerebral blood flow (rCBF) accompanying seizures, and to assess the utility of ictal activation PET scanning as a noninvasive clinical tool for localization of epileptogenic foci, we used pentylenetetrazole (PTZ) to induce seizures during O-15-water positron emission tomography (PET) CBF measurement in 15 patients with uncontrolled complex partial seizures (CPS) who had been referred for surgical evaluation. Continuous EEG monitoring was performed during the PET scans. After baseline scans were obtained, each patient was injected with 150-300 mg PTZ. Two patients had generalized tonic-clonic seizures (GTCs). CBF increases were asymmetrical. Two patients (in 1 the seizure occurred spontaneously, without PTZ injection) who had CPS had bitemporal 70-80% increases in CBF. Thalamic CBF increased during both CPS and GTCS. Five patients had an increase in focal EEG interictal abnormality, accompanied by focal flow decreases in 3. PTZ injection not accompanied by clinical seizures did not increase CBF. Partial seizures may be associated with bilateral increases in CBF, and subcortical gray regions are involved in ictal activation.