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

Abstract

Alpha-[11C]methyl-L-tryptophan (alpha-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). To determine whether alpha-MTrp PET can detect neocortical changes in patients with PVNH. 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 alpha-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. Alpha-MTrp PET revealed increased cortical uptake in two of four patients. The area of increased alpha-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. alpha-MTrp PET did not show increased uptake in the heterotopic nodules in any of the patients. Alpha-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 alpha-MTrp PET may be useful, in conjunction with other evaluations, in localizing epileptic focus in patients with PVNH and refractory seizures.