Temporal Uptake of ?-[11C] Methyl-L-Tryptophan in Patients with Intractable Temporal Lobe Epilepsy: Evaluation with Positron Emission Tomography.
Abstract number :
1.207
Submission category :
Year :
2000
Submission ID :
2412
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Jun Natsume, Marco Fedi, Pedro Rosa, Andrea Bernasconi, Neda Bernasconi, Akio Nakai, Yoshitaka Kumakura, Francois Dubeau, Frederick Andermann, Robert Lisbona, Mirko Diksic, Montreal Neurological Institute, Montreal, QC, Canada; Montreal Neurological Hosp
Objective: To evaluate whether ?-[11C] methyl-L-tryptophan (?-MTrp) positron emission tomography (PET) can help lateralize the epileptogenic focus in patients with intractable temporal lobe epilepsy (TLE). Background: The most common pathologic finding in pharmacologically intractable TLE is hippocampal sclerosis. PET studies with 2-[18F]-fluoro-deoxy-glucose (FDG) show that the interictal hypometabolic zone includes the temporal lobe ipsilateral to the epileptic focus. ?-MTrp PET allows more specific assessment of neuronal activity and has been developed as a tracer to measure serotonin synthesis in vivo. Design/Methods: We studied three patients with intractable TLE. All underwent comprehensive presurgical workup including video-EEG telemetry. One had unilateral hippocampal atrophy, and two had no atrophy. The tracer ?-MTrp was injected intravenously. Following injection, dynamic PET scans were performed. We performed a FDG PET scan on a different day. PET images were coregistered with high-resolution MRI. ROIs (regions of interest) were placed on each anatomical region on the MRI. An asymmetry index (AI) of each homologous pair was used to quantify the regional alteration: AI=(C-I)/[(C+I)/2]?100, where I is the mean value in the ROI on the side ipsilateral to the EEG lateralization, and C is its homologue on the contralateral side. Results: The mean value of the ?-MTrp uptake constant in the hippocampus ipsilateral to the EEG focus was higher than the contralateral side in all three patients. AI of the hippocampus in ?-MTrp PET was -19%, -6%, and -8%. Visual inspection of the FDG PET showed clear focal hypometabolism in the temporal lobe ipsilateral to the EEG focus in two patients. AI of the whole temporal lobe in FDG PET was 13%, 9%, and 6%. Conclusion: ?-MTrp PET showed high uptake of ?-MTrp in the epileptogenic hippocampus due to the increased metabolism of tryptophan. This could be related to high serotonin synthesis, an activation of the kynurenine pathway or both of these in an uneven proportion. ?-MTrp PET might clarify the pathophysiology and lateralize the epileptogenic focus in TLE.