18-FDG PET in Patients with Temporal Lobe Epilepsy and Normal MRI Scans.
Abstract number :
3.170
Submission category :
Year :
2001
Submission ID :
2999
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
P.A. Garcia, MD, Neurology, UCSF, SF, CA; K.D. Laxer, MD, Neurology, UCSF, SF, CA; R.C. Knowlton, MD, Neurology, UAB, Birmingham, AL; D.L. Kraemer, MD, Swedish Epilepsy Center, Seattle, WA; D.G. Vossler, MD, Swedish Epilepsy Center, Seattle, WA; T. Alsaad
RATIONALE: 18FDG PET is a sensitive test for identifying the seizure focus in patients with TLE and it rarely provides falsely lateralizing information. The adjuntive localizing information provided by PET may be especially valuable in patients without localizing MRI scans. We wished to assess the localizing value of 18FDG PET in patients with TLE and normal MRI scans.
METHODS: We initially identified all patients at UC San Francisco and Swedish Hospital who had 18FDG PET studies in preparation for anterior temporal resection between 1995 and 2000. In order to insure that the presurgical localization was correct, only patients who became seizure-free after surgery were included in our study. Patients were classified as having MRI evidence for mesial temporal sclerosis (MTS) or normal MRI. Patients with other MRI lesions were excluded. We classified the reported 18FDG uptake as symmetric, asymmetric and concordant with the seizure focus or asymmetric and discordant with the focus. The degree of asymmetry was characterized qualitatively. Two tailed Fisher[ssquote]s exact test was used to compare the incidence of discordant PET asymmetries in patients with normal MRI scans to the incidence in patients with MRI evidence of MTS.
RESULTS: Fifty-eight patients became seizure-free after surgery (44 with MRI evidence for MTS and 14 with normal MRI). In the patients with normal MRI, 9 had PET asymmetries concordant with the seizure focus, 2 had symmetric studies and 3 had PET asymmetries discordant with the seizure focus. In patients with MRI evidence for MTS 39 had concordant PET asymmetries, 4 had symmetric studies and 1 had a discordant asymmetry. Discordant asymmetries were more common in patients with normal MRI scans compared to patients with MRI evidence of MTS(3/14 vs 1/44 p=0.04). The discordant asymmetries were typically mild.
CONCLUSIONS: Asymmetric 18FDG uptake discordant with the seizure focus is rare but may occur more frequently when the MRI is normal. The degree of discordant asymmetry is typically mild. We recommend that only prominent 18FDG PET asymmetries be used to localize the seizure focus in patients with normal MRI scans.
Support: Supported by NIH Grant R01-NS31966