Abstracts

Proton magnetic resonance spectroscopy(1H-MRS) yield a biochemical evaluation of structurally abnormal tissue.In addition,a decrease in NAA has been detected in the seizure focus of patients with temporal lobe epilepsy.This study was designed to evaluate patients presenting malformations of cortical development(MCD) by 1H-MRS;to compare spectroscopic findings between different types of MDC and to correlate them with epileptogenicity
25 patients with history of epilepsy and MCD were studied in a 1.5 Tesla MR.[underline]1H MRS[/underline]:Relative metabolite concentrations(NAA/CHO,NAA/CR,CHO/CR) were measured.For the analysis we selected voxels in areas presenting MCD. When the lesion was unilateral, we compared it with areas in the normal contralateral side.1H-MRS was not done within 48 h of a seizure, except in 6 patients with daily episodes. The normal value was established with an age-matched group of healthy volunteers(n=30),comparing each region with a voxel located on the same position in the volunteer. 1H-MRS results were correlated with clinical and EEG data.[underline]Clinical Evaluation[/underline] was performed with a standard questionnaire developed for the project. The main analyzed factors were:age of onset,epilepsy duration,frequency,refractoriness and severity.[underline]Neurophysiological Investigation[/underline] included EEG and video-EEG for diagnosis.A 2-h EEG was performed 2-4 h before 1H-MRS, that was used to calculate the rate of interictal spiking, counted in at least 2-3 epochs of 5[apos].Neuroimaging results were correlated with EEG data considering n[deg] discharges/min, degree of background abnormalities and distribution (focal or widespread).We used Kruskal-Wallis and Mann-Whitney test for statistical analysis
10 patients had nodular heterotopia;4 band heterotopia;6 polymicrogyria;3 schizencephaly and 2 hemimegalencephaly.NAA/CR ratio was decreased in all abnormal areas, and in the patient[rsquo]s normal contralateral side,a decreased NAA/CR ratio was also detected in comparison with the same areas in the control group.No differences were observed among distinct groups of MCD.We found no significant correlation between epilepsy related-factors (frequency, refractoriness and duration) and metabolite rates.No apparent correlation was observed with the rate of discharges, including patients with continuous discharges, the distribution of these discharges, the concordance with seizure focus and the presence/degree of background disorganization.
The neuronal migration disorders and the contralateral side presented decreased NAA/CR ratios in comparison to controls that suggest functional or structural abnormalities in the apparently normal side.Spectroscopic findings were not correlated with epilepsy and EEG, implying that the relationship between metabolic abnormalities,MCD and the mechanism of epilepsy is complex and 1H-MRS findings may not predict the epileptogenicity of these lesions.