Focal functional deficits in temporal lobe epilepsy on PET scans and the intracarotid amobarbital procedure: Comparison of patients with unitemporal epilepsy with those requiring intracranial recordings

Purpose: To analyze the relationship between the intracarotid amobarbital p rocedure (IAP) and positron emission tomography (PET) and study the lateral izing value of these tests in patients with unitemporal epilepsy and those requiring intracranial recordings. Methods: We compared 51 patients with unitemporal epilepsy (group 1) with 2 6 patients in whom surface recordings failed to reveal a distinct unitempor al focus, necessitating invasive recordings (group 2). Results: The brain magnetic resonance imaging (MRI) scans for group 1 showe d mesial temporal sclerosis in 70.5% of the patients. PET showed unilateral temporal hypometabolism in 88%. In addition, 74.5% of the patients in grou p 1 had impaired memory on the epileptogenic side on the IAP. and 89.4% of those patients also had ipsilateral temporal hypometabolism on PET scans. A ll the group 1 patients underwent temporal resections. The pathologic exami nation showed hippocampal sclerosis in 72% of the patients. Eighty percent of group 1 patients became seizure free, and 16% had rare seizures (follow- up, 2-7 years). MRIs for group 2 showed mesial temporal sclerosis in 31%, o f the patients; PET scans showed temporal hypometabolism in 39%. The IAP wa s lateralized in 47.8%. Sixty-nine percent had temporal lobe resections. Th e pathologic examination showed hippocampal sclerosis in 44% of the patient s. Forty-four percent of group 2 patients became seizure free, and 27.7% ha d rare seizures (follow-up, 2-8 years). Conclusions: Ninety-six percent of the patients with unitemporal foci had f ocal functional deficits on the epileptogenic side on 18-fluorodeoxyglucose -(FDG) PET scans, the IAP, or both. The results of the FDG-PET were predict ive of impaired memory on the IAP. Memory impairment contralateral to the t emporal hypometabolism found on the PET scans was never seen. These patient s had an excellent outcome. In contrast, <50% of the patients requiring int racranial recordings had focal functional deficits, suggesting that more a diffuse pathology may account for their less favorable outcome.