α-[11C]methyl-L-tryptophan uptake in patients with periventricular nodular heterotopia and epilepsy

Abstract

Background: α-[11C]methyl-L-tryptophan (α-MTrp) positron emission tomography (PET) is a promising tool in the localization of the epileptogenic area in selected group of focal epilepsy patients. Electrophysiological evidence suggests the involvement of the neocortex in periventricular nodular heterotopia (PVNH). Purpose: To determine whether α-MTrp PET can detect neocortical changes in patients with PVNH. Methods: Four patients (2 male, mean age 28, range 23-35 years) with PVNH and intractable seizures were studied. The functional image in each patient was compared with those from 21 healthy controls (mean age 34.6 ± 14.2 years) by using statistical parametric mapping (SPM). The location of increased α-MTrp uptake was compared with the location of the EEG focus. A significant cluster was defined as a cluster with a height p = 0.005 and an extent threshold 100. Results: α-MTrp PET revealed increased cortical uptake in two of four patients. The area of increased α-MTrp uptake in one patient was widespread. In the other patient, the area of increased uptake did not include the region where most seizures were generated on EEG. α-MTrp PET did not show increased uptake in the heterotopic nodules in any of the patients. Conclusions: α-MTrp PET suggests abnormal metabolism of tryptophan in the neocortex. The increased uptake may be diffuse and may not co-localize with the EEG focus. This preliminary study suggests that α-MTrp PET may be useful, in conjunction with other evaluations, in localizing epileptic focus in patients with PVNH and refractory seizures. © 2008 International League Against Epilepsy.