Epilepsy: Clinical applications of diffusion tensor imaging

Abstract

Diffusion MRI has many potential advantages over conventional anatomic imaging for detecting and characterizing both acute seizures and epilepsy. This chapter reviews how diffusion tensor imaging (DTI) and tractography have provided many novel insights into epilepsy-induced changes to the functional and structural organization of the hippocampus, cortex, and underlying white matter for patients with various epilepsy disorders. In temporal lobe epilepsy (TLE) patients, DTI has demonstrated that (1) there are extensive, often bilateral white matter and extrahippocampal changes; (2) significant white matter structural differences between right and left temporal lobe epilepsy; (3) seizure propagation and white matter reorganization may be more widespread when seizures are generated in the dominant cerebral hemisphere due to greater pre-existing connectivity; and (4) the extent of white matter and hippocampal diffusion changes can correlate with the duration or age of onset of seizures, supporting the hypothesis that seizures may damage the brain in a dose-dependent fashion. Furthermore, white matter assessment in TLE patients prior to surgical resection can predict visual field defects based on the extent of resection and also provide objective surrogate markers for language lateralization, verbal, and memory function. In malformations of cortical development or tuberous sclerosis, DTI also demonstrates clinically relevant abnormalities of structural organization both in focal lesions and in nearby or remote normal-appearing white matter. At present, DTI is rapidly expanding our knowledge of functional and structural changes associated with various seizure disorders and is likely to have a growing positive impact on the clinical management of epilepsy patients. Several potential future directions for research are discussed.