Abstracts

Rationale: Concepts and classifications of epilepsy syndromes are currently under debate. This is particular true for the dichotomy of focal versus generalized epilepsy syndromes. According to the latest report of the ILAE commission on Classification and Terminology these terms should be abandoned, but clinically well-defined subsyndromes as the Juvenile myoclonic epilepsy (JME) are still used both by clinicians and scientifics. By definition, JME is characterized by the absence of structural brain abnormalities and considered to be a functional disturbance. Advanced magnetic resonance imaging (MRI) studies of JME have reavealed subtle focal changes predominantly in the frontal lobe and the thalamus. Our study aimed to demonstrate further evidence for "focality" in JME patients by using Voxel based morphometry (VBM), an operator-independent method for whole-brain analysis. Methods: All patients were diagnosed and treated at one center, at the Epilepsy Center Bethel, Bielefeld, Germany. 41 patients (19 women, mean age 30,2 ±15,5) with the confirmed diagnosis of JME were identified. Data were compared with 44 healthy controls (21 women, mean age 36,0 ±11,3). All subjects underwent 1, 5 T MRI-scanning. Subsequently magnetic resonance voxel-based morphometry analysis (VBM) was performed using SPM5 in order to identify abnormalities in gray matter (GM) volume between patients and controls. Image postprocessing consisted of spatial normalization, automated grey matter segmentation, modulation, smoothing, and voxel-wise statistical analysis between the 2 groups was performed. Statistical level selected was a p < 0.05 with correction for multiple comparisons (family-wise error). Results: VBM in this JME patient group revealed significantly increased grey matter (GM) volume (p < 0;05) in the bilateral medial frontal gyrus (coordinates x= -13, y= 60, z=0, Z-score 5,17, voxelcluster 125; x= 15, y= 58, z=3, Z-score 4,85, voxelcluster 32) and significantly reduced (GM) volume bilateral in the insula (coordinates x= -33, y= 21, z=-9, Z-score 4,68, voxelcluster 12; x= 42, y= -6, z=13, Z-score 4,93, voxelcluster 255; x= 41, y= 2, z=2, Z-score 4,79, voxelcluster 128; x= 37, y= 19, z=1, Z-score 4,72, voxelcluster 40) compared to controls (p < 0.05). This particular group of JME patient was further characterized by a rather unfavorable clinic course showing pharmacoresistence in 34%. Conclusions: Our results suggest the enforced implication of the frontal and insular cortex in JME patients and support the concept of an epileptogenic- thalamo-cortical network in JME. We assume that the pronounced abnormalities are a reflection of this specific JME cohort with unfavorable disease course. We did not find any clearly lateralizing abnormalities in our study population. Our data detecting subtle structural changes in JME are encouraging to perform further studies focusing on functional-structural relationships in patients diagnosed with idiopathic "generalized" epilepsies.