Postictal diffusion-weighted imaging for the localization of focal epileptic areas in temporal lobe epilepsy

Purpose: Diffusion-weighted MR imaging (DWI) is a novel technique to deline ate focal areas of cytotoxic edema of various etiologies. We hypothesized t hat DWI may also detect the epileptogenic region and adjacent areas during the ictal and early postictal periods in patients with temporal lobe epilep sy (TLE). Methods: We studied patients with intractable TLE (n = 9), due to hippocamp al sclerosis (HS, n = 7), left mesial temporal lobe tumor (n = 1), and of u nknown etiology (n = 1). Informed consent was obtained before inclusion in the study. All patients with single short seizures were scanned immediately after EEG-documented seizures (between 45 and 150 min); one of two patient s in status was scanned 14 h after cessation of seizures. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) m aps. Results: We found significant decreases in ADC postictally in one of six pa tients with TLE due to HS and single short seizures. One patient with an in completely resected temporal lobe tumor also exhibited ADC abnormalities. O ne patient in focal status epilepticus revealed a decrease in ADC, and one patient with a continuous aura had no DWI abnormality. Conclusions; Postictal DWI technique may occasionally help delineate epilep tic areas in some patients with TLE. Yield is low in patients with HS and s ingle short seizures: it may be higher. in patients with tumor or status ep ilepticus.