3.2 Magnetic resonance imaging (MRI) is clearly the structural imaging modality of choice for investigating patients with epilepsy and is superior to radiographic CT in terms of both sensitivity and specificity for identification of small lesions and abnormalities of the cerebral cortex. Occasionally, CT may be useful as a complementary imaging technique in the detection of cortical calcifications, particularly in patients with congenital or acquired infections. In nonacute circumstances, MRI is preferable to CT as the first imaging investigation. Imaging should include TIand T,-weighted sequences to cover the whole brain in a minimum of two orthogonal planes, with the minimum slice thickness obtainable on the scanner used. Gadolinium contrast enhancement is not necessary in routine cases but may be helpful in selected cases if the 3.3