Cerebral metabolism of the remote area after epilepsy surgery

To clarify whether epilepsy surgery improves cerebral metabolism, pre- and postoperative positron emission tomography (PET) scans were performed, with special reference to hypometabolism outside the resected epileptogenic zones in nine patients (8 males, 1 female) with medically intractable complex partial seizures and multiple hypometabolic zones. Seven patients underwent unilateral anterior temporal lobectomy, one patient underwent selective amygdalohippocampectomy, and one patient underwent parieto-occipital cortical resection and anterior temporal lobectomy. PET scans were obtained at least 6 months after surgery. Eight patients became seizure-free, and one patient had fewer than three seizures per year. Four patients showed improved glucose metabolism in the formerly hypometabolic zones, which were remote to the surgical site and ipsilateral to the epileptogenic foci. Five patients, who showed bilateral temporal hypometabolism preoperatively, had contralateral temporal hypometabolism after surgery. The relative glucose uptake in four of these patients showed increased metabolism of the adjacent lobes ipsilateral to the surgical site. The lobes that showed increased glucose metabolism after surgery were mostly frontal. Hypometabolism is reversible in the ipsilateral remote area, and may be caused by inhibition via the intercortical pathway. Contralateral temporal hypometabolic zones that persist after surgery may be caused by a different mechanism, and neither indicate the presence of seizure foci nor affect the seizure outcome.