MRI technique for epilepsy diagnosis:
The sensitivity of MRI for detecting abnormalities depends on the pathological substrate, the MRI techniques applied, and the experience of the interpreting physician. A routine optimal MRI protocol should include T1 and T2 weighted, proton density and fluid attenuated inversion recovery (FLAIR) sequences. These contrasts need to be acquired in at least two orthogonal planes covering the whole brain, using the minimum slice thickness possible. An oblique coronal plane, orientated perpendicular to the long axis of the hippocampus, gives the best definition of medial temporal lobe structures. In general, T1 weighted images give the best definition of the anatomy and differentiate grey and white matter, while T2 weighted images provide high sensitivity for detecting pathology in the brain. A three dimensional T1 weighted volume sequence with a partition size of 1.5 mm or less should be included as these images may be reformatted in any orientation and used for post-acquisition processing such as measuring hippocampal volumes. FLAIR imaging produces heavy T2 weighting and suppresses signal from cerebrospinal fluid (CSF). This provides high lesion contrast in areas close to CSF and enables anatomical detail to be seen with greater conspicuity than with conventional T2 weighted sequences. Gadolinium does not improve the sensitivity of MRI in patients with epilepsy, but may be useful to characterise intracerebral lesions associated with breakdown of the blood–brain barrier.