Abstracts

RATIONALE: To investigate neuronal dysfunction in the thalami of patients with juvenile myoclonic epilepsy (JME) using proton magnetic resonance spectroscopy (MRS).
METHODS: We studied 10 consecutive patients (5 women) with JME with mean age of 31,6 years (ranging from 17 to 44 years). All patients had seizure onset in late childhood-teenage years, normal neurological examination, typical EEG of JME and normal high resolution MRI. MRI and MRS examinations were performed on an Elscint 2T scanner (Prestige, Haifa, Israel). We performed single voxel proton MRS using PRESS sequence (TR= 1500 ms, TE=135ms, NEX=200) over the right and the left thalami of patients and 10 healthy volunteers (five men) with mean age of 30,3 (ranging 22 to 36 years). After the acquisition of scout anatomical images in axial planes for localization of thalami, one single voxel (2x2x2 cm) was placed over the region of interest (ROI). Each subject underwent two single voxel MRS, one for right and one for left thalamus. Prior to the acquisition, a localized shimming at ROI was performed to ensure adequate field homogeneity, followed by water suppression adjustment. Spectra were post-processed and resonance intensities were determined from peak areas by integration using software supplied by the machine manufacturer. We measured signals from N-acetyl compounds, mainly the neuronal marker N-acetylaspartate (NAA) at 2.01 ppm, choline-based compounds (Cho) at 3.2 ppm and creatine and phosphocreatine contained compounds (Cr) at 3.0 ppm. Spectra with broad peaks and poor separation of individual peaks were excluded from analysis. Values below 2 standard deviations (SD) from controls were considered abnormal. We performed Student[scquote]s t-test to evaluate group differences.
RESULTS: Thalami NAA/Cr ratios were significantly decreased in JME patients (left side 1.58 [plusminus] 0.26; right side 1.5 [plusminus] 0.15) as compared to controls (left side 1.98 [plusminus] 0.18, right side 1.88 [plusminus] 0.15) (p=0.0001 and p=0.007 respectively). In addition, 9 of the 10 patients had abnormal NAA/Cr values in at least one of the thalami ([lt]2SD from the mean of controls).
CONCLUSIONS: This study shows evidence of neuronal dysfunction in the thalami of patients with JME supporting the theory of abnormal thalamo-cortical circuitry as an underlying mechanism for seizure generation in this form of generalized epilepsy.
[Supported by: Funda[ccedil][atilde]o de Amparo `a Pesquisa do Estado de Sao Paulo - FAPESP, Brazil]