THE VALUE OF PET SCAN (AND MRI AND WADA TEST) IN PATIENTS WITH BITEMPORAL EPILEPTIFORM ABNORMALITIES

Background: Lateralization remains difficult in patients with bitempor al epileptiform abnormalities. Objective: To evaluate the reliability of the interictal fluorodeoxyglucose F18-positron emission tomographic (PET) scan in this setting. Methods: We analyzed PET scan findings in 25 patients who required bilateral depth electrodes for lateralizatio n of temporal lobe epilepsy. The contribution of magnetic resonance im aging and the intracarotid amobarbital procedure was also analyzed. Re sults: Positron emission tomographic scan revealed lateralized hypomet abolism in 15 patients. This was in agreement with the depth evaluatio n in 10 cases (67%). In five cases (33%), the PET and depth findings w ere in disagreement, with no predominant side of seizure origin by dep th electroencephalography (EEG) in four cases and PET lateralization o pposite to depth findings in one case. In 10 of the 25 patients, PET s cans could not lateralize hypometabolism to one temporal lobe, of whic h six were confirmed by depth EEG not to have a predominant side of se izure onset, The overall sensitivity of PET for concordant lateralized seizure onset was 67%. Ten of 14 patients who underwent a lobectomy h ad a successful outcome, including three of four patients whose tempor al lobe epilepsy was lateralized by depth EEG but not by PET. One pati ent had PET lateralization opposite to the depth EEG and side of surge ry and failed to improve. Conclusions: In this highly selected group o f patients, the lateralizing value of PET and magnetic resonance imagi ng was somewhat diminished, and the intracarotid amobarbital procedure was not found useful for lateralization. Positron emission tomography and magnetic resonance imaging, when pointing to the side opposite de pth EEG, may indicate a poor prognosis.