MAGNETIC-RESONANCE-IMAGING OF TEMPORAL-LO BE EPILEPSY

MR has gained more and more importance in the evaluation of patients w ith temporal lobe epilepsy (TLE). Until recently, hippocampal sclerosi s (which is the most frequent cause of temporal lobe epilepsy, account ing for 50-70 % of the cases) could not be identified reliably. Using optimized magnetic resonance imaging techniques, hippocampal sclerosis can now be evidenced in a large proportion of patients with TLE. Tumo rs (10-15%), developmental abnormalities (5-7%), vascular malformation s (mostly cavernous angiomas, 1-5%), and traumatic scars (5-10%) repre sent the other structural lesions associated with TLE. Studies of larg e series of patients with intractable epilepsy or with varying severit y have shown that in only 8,5% and 20%, respectively, a specific imagi ng abnormality was not found. Specific MR sequences increase the diagn ostic value of MR (coronal images perpendicular to the axis of the hip pocampal formations, three-dimensional T1 weighted images, inversion r ecovery images, volumetry or more specific processes such as T1 and T2 relaxometry or spectroscopy). MR also helps guide placement of intra- cerebral and subdural electrodes in surgically relevant cases. All the se results have given greater importance to MR in the definition of th e epileptic syndrome of TLE and should probably be integrated in the c riteria of international classifications.