title: 1H MR spectroscopy of mesial temporal lobe epilepsies treated with Gamma knife.
abstract: Proton MR spectroscopy was used to observe long-term post-irradiation metabolic changes in epileptogenic tissue and in the contralateral parts of the brain which are not available with conventional imaging methods. We studied these changes in the temporal lobe in six patients, following radiosurgery on the amygdala and hippocampus. (1)H MR spectroscopy at 1.5 T with short and long echo times (TE=10 and 135 ms) were used together with standard MR imaging sequences (T1-, T2-weighted). The treatment was performed by Leksell Gamma Knife with a dose of 50 Gy to the center and a 50% isodose to the margin of the target, represented by the mean volume of approximately 7.5 ml. Magnetic resonance imaging and MR spectroscopy examinations were performed at least once per year for 3 years. The most significant changes in spectra were observed approximately 1 year after the irradiation when edema in irradiated area was observed and strong signal of lipids was identified. Later, edema and lipid signals disappeared and follow-up was characterized by a decrease of NAA, Cr, and Cho concentrations in the ipsilateral region of the brain to the irradiation (LCModel calculation from voxel of interest 3.8-4.5 ml positioned into the centrum of target volume). The concentration of NAA, Cr, and Cho after radiosurgery was significantly different from control values ( p<0.05) and also from concentrations in the contralateral part of the brain ( p<0.05). In the contralateral part, the concentration of NAA was significantly increased ( p<0.05) (NAA: before treatment 8.81, after treatment 11.33 mM). No radiotoxic changes were observed in the contralateral part of the brain or behind the area of target volume. The MR spectroscopy findings precluded MRI observation and MRS results completed data about the development of radiotoxic changes in the target volume.
authors.affiliation: MR Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Vídenská 1958/9, 140 21 Prague, Czech Republic. miha@medicon.cz
authors.forename: Milan
authors.initials: M
authors.lastname: Hájek
authors.forename: Monika
authors.initials: M
authors.lastname: Dezortová
authors.forename: Roman
authors.initials: R
authors.lastname: Liscák
authors.forename: Josef
authors.initials: J
authors.lastname: Vymazal
authors.forename: Vilibald
authors.initials: V
authors.lastname: Vladyka
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000528:radiation effects; D001921:Brain / Q000378:metabolism / Q000528:radiation effects; D001932:Brain Neoplasms / Q000175:diagnosis / Q000378:metabolism / Q000601:surgery; D002794:Choline / Q000378:metabolism / Q000528:radiation effects; D003401:Creatine / Q000378:metabolism / Q000528:radiation effects; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000378:metabolism / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D018698:Glutamic Acid / Q000378:metabolism / Q000528:radiation effects; D005973:Glutamine / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000528:radiation effects; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011183:Postoperative Complications / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism; D011832:Radiation Injuries / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism; D011836:Radiation Tolerance / Q000502:physiology; D016634:Radiosurgery / Q000009:adverse effects; D012640:Seizures / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism; D013997:Time Factors; D017211:Treatment Failure
chemical_list: D008055:Lipids; D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline