Summary:Purpose: Diffusion-weighted magnetic resonance imaging (DWI) after focal status epilepticus has demonstrated focal alterations of the apparent diffusion coefficient (ADC) in the epileptogenic zone. We hypothesized that localized dynamic alterations of brain diffusion during the immediate postictal state will be detectable by serial DWI and correlate with the epileptogenic zone.Methods: Nine adult patients (four men, five women) with medically intractable epilepsy were prospectively examined with a total of 25 DWI scans taken 2-210 min after a seizure.Results: The interictal ADC was significantly (p < 0.05) elevated in the ictogenic hippocampus in all patients with temporal lobe epilepsy. The following postictal changes of the ADC were seen: (a) decreases by maximally 25-31%, which were most pronounced in the epileptogenic zone (n ‫ס‬ 2); (b) generalized ADC changes after generalized seizures (n ‫ס‬ 1) or prolonged complex partial seizures (n ‫ס‬ 2); (c) no major changes after short-lived seizures or if the time to first DWI scan was >15 min or both (n ‫ס‬ 3); and (d) widespread bilateral ADC increases after a flumazenil-induced seizure (n ‫ס‬ 1).Conclusions: ADC changes seen during serial postictal DWI are complex and appear to reflect origin and spread of the preceding seizure. A delineation of the epileptogenic zone appears to be possible only in complex-partial seizures of >60 s duration that do not secondarily generalize. Key Words: Diffusion-Epilepsy surgery-MRI-Epileptogenic focusPostictal.Transient postictal phenomena attributed to the epileptogenic zone have been observed clinically (e.g., hemiparesis), by EEG/electrocorticogram (ECoG) recordings (slow foci and attenuation), and by comparison of interictal with ictal single-photon emission computed tomography (SPECT; hypoperfusion vs. hyperperfusion) (1-4). They provide good to excellent data as to the localization or lateralization of the epileptogenic zone.Descriptions of focal postictal alterations in structural magnetic resonance imaging (MRI) or CT are limited to a few patients and have mainly been based on T 2 imaging sequences (5-10). They appeared to rely on long-lasting seizure activity such as focal status epilepticus (6-8,11). In addition, local postictal hyperperfusion was seen by Penfield during epilepsy surgery and documented by angiography (12,13).Diffusion-weighted MR imaging (DWI) is a noninvasive tool for the early detection of acute ischemic lesions in humans and in animal models of focal status epilepticus (14-17). Furthermore, data from animal experiments in epilepsy suggest that brain-diffusion changes after focal status epilepticus may persist for hours and even days. Experiences in humans have targeted investigation of focal status epilepticus and are limited to a small number of patients (11,(18)(19)(20)(21). In these patients, postictal decrease of the apparent diffusion coefficient (ADC) and increase of the DWI signal were seen (22,23).Latest-technology DWI imaging now allows highresolution, serial measurements of diffu...

Summary:Purpose: After focal status epilepticus, focal alterations of the apparent diffusion coefficient (ADC) have been demonstrated in the epileptogenic zone by using diffusionweighted magnetic resonance (MR)imaging (DWI). Effects of flumazenil on an epileptogenic focus have been demonstrated by EEG recordings, but not by functional MRI. We hypothesized that dynamic spatiotemporal alterations of brain diffusion of the epileptogenic focus after application of flumazenil will be detectable by DWI and correlate with the epileptogenic zone.Methods: Twelve adult patients considered for epilepsy surgery with medically intractable temporal lobe epilepsy (TLE; n ‫ס‬ 7), extratemporal lobe epilepsy (ETE; n ‫ס‬ 2), and TLE+ETE (n ‫ס‬ 3) were prospectively examined with DWI interictally (serving as baseline) and 10 min after application of 1 mg flumazenil i.v. Results:The baseline interictal ADC was significantly elevated in the hippocampus on the ictogenic side in the patients with TLE (p ‫ס‬ 0.002) as compared with healthy volunteers. The following changes of the mean ADC were seen in different regions of interest (ROIs) after injection of flumazenil: decreases in the hippocampus on the seizure-onset side by 14.8% (p ‫ס‬ 0.005); decreases in the parahippocampal gyrus on both sides by 6.8% (epileptogenic side; p ‫ס‬ 0.044) or 7.9% (nonepileptogenic side; NS), respectively; decreases in the cortex on the nonictogenic side by 7.9% (p ‫ס‬ 0.047); and no significant changes of the ADC in the other ROIs.Conclusions: ADC decreases measured after application of flumazenil were seen in the seizure-onset zone as revealed by EEG and structural MRI and are an indicator of focus localization in patients with TLE.

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