Preoperative Functional Localization

Identifying and visualizing the location of eloquent cerebral functions and critical white matter tracts is important for mitigating collateral damage in the neurosurgical treatment of drug-refractory focal epilepsy. Functional MRI can lateralize and broadly localize eloquent functions including language, memory, motor, sensory, and visual functions. For precise localization, when resecting close to eloquent areas, precise mapping of the cortex with direct electrical stimulation is generally needed. Tractography, derived from diffusion MRI, can infer the location of the major critical white matter tracts: the optic radiation, corticospinal tracts, and language-related tracts of arcuate fasciculus and inferior fronto-occipital fasciculus. Data must be acquired very carefully and interpreted cautiously but can be a useful adjunct to precise neurosurgical navigation to avert causing new deficits.