Abstracts

RATIONALE:Interictal PET imaging using amino acids such as [11C]-?-methyl-tryptophan and [11C]-methionine have been used to identify epileptogenic foci in patients with partial epilepsy. There are few reports of ictal compared with interictal PET scans superimposed on SPECT and MRI. Co-registration of PET studies using such tracers with interictal and ictal SPECT images using technetium-99m-hexamethyl-propyleneamine oxime (HMPAO) and MRI may improve localization of epileptogenic foci even in the absence of a MRI defined lesion. We report a patient using such a multimodal approach. METHODS: A medically refractory patient with focal seizures was studied. After informed medical and ethical approval, the following radioisotopes studies were performed: a dynamic 60 minute PET scan with [11C]-a-methyl-tryptophan and a [11C]-methionine. HMPAO-SPECT using a GE dual head camera was performed at onset of a seizure and during the interictal period. EEG recordings were obtained during the PET scanning. High resolution T1 3D-MRI acquisition was performed in a Philips 1.5T Gyroscan. Imaging modalities were co-registered and resampled on standard stereotaxic space. RESULTS: A 59-year-old, woman, presented supplementary motor seizures since age 16 years. Prolonged video EEG monitoring was inconclusive and her MRI was normal. Interictal [11C]-?-methyl-tryptophan PET scan did not showed abnormalities but during [11C]-methionine PET study the patient had a partial seizure, which showed increased uptake in the mesial aspect of the left fronto-parietal cortex. Interictal and ictal SPECT were not localizing. CONCLUSIONS: These observations suggest that during the ictal and interictal events perfusion and trapping of amino acids tracers may be different. PET imaging with amino acids may contribute to determination of epileptogenic foci.