Diffusion mapping applied to mesial temporal lobe epilepsy - Preliminary observations

Objective: To evaluate whether diffusion mapping could lateralize intractab le seizures in mesial temporal lobe epilepsy (MTLE) patients. Background: A nimal seizure models show acute postictal depression of the apparent diffus ion coefficient of water (ADC,), interictal normalization, then chronic ele vation. Methods: The hippocampal plane was imaged with five diffusion weigh tings along each axis. Three orthogonal ADC, maps were averaged to produce an isotropic ADC, map. Results: In all eight MTLE patients, ADC, was elevat ed by a mean of 10 +/- 3% (p < 0.01, paired t-test) interictally in the ips ilateral hippocampus, where side of seizure focus was determined electrogra phically with corroboration by volumetric MRI studies. Measured ADC, values in phantoms and five normal brains agree with published values. Conclusion s: Brain tissue with interictally increased ADC, may represent an epileptog enic region with neuronal loss, gliosis, and expanded extracellular space ( hippocampal sclerosis). Thus, diffusion mapping may confirm seizure lateral ization.