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Postictal diffusion-weighted imaging for the localization of focal epileptic areas in temporal lobe epilepsy
1Department of Neurology, The Cleveland Clinic Foundation, 9500 Euclid Ave., Cleveland, Ohio 44195, U.S.A. diehlb@ccf.org
Purpose:
Diffusion-weighted MR imaging (DWI) is a novel technique to delineate focal areas of cytotoxic edema of various etiologies. We hypothesized that DWI may also detect the epileptogenic region and adjacent areas during the ictal and early postictal periods in patients with temporal lobe epilepsy (TLE).
Methods:
We studied patients with intractable TLE (n = 9), due to hippocampal sclerosis (HS, n = 7), left mesial temporal lobe tumor (n = 1), and of unknown 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 patients in status was scanned 14 h after cessation of seizures. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) maps.
Results:
We found significant decreases in ADC postictally in one of six patients with TLE due to HS and single short seizures. One patient with an incompletely resected temporal lobe tumor also exhibited ADC abnormalities. One 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 epileptic areas in some patients with TLE. Yield is low in patients with HS and single short seizures: it may be higher in patients with tumor or status epilepticus.
Insights
Diffusion-weighted MR imaging (DWI) may occasionally help identify epileptic regions in temporal lobe epilepsy (TLE) patients. This technique shows promise for tumors or status epilepticus, but has a low yield in hippocampal sclerosis.
Area of Science:
- Neuroimaging
- Epileptology
- Radiology
Background:
- Diffusion-weighted MR imaging (DWI) is a novel technique for detecting cytotoxic edema.
- Its potential to identify epileptogenic zones in temporal lobe epilepsy (TLE) during ictal and postictal periods is unexplored.
Purpose of the Study:
- To investigate the utility of DWI in detecting the epileptogenic region and adjacent areas in patients with TLE during ictal and early postictal periods.
- To hypothesize that DWI may detect these regions.
Main Methods:
- Studied 9 patients with intractable TLE (7 with hippocampal sclerosis, 1 with temporal lobe tumor, 1 of unknown etiology).
- Scanned patients postictally (45-150 min after seizures or 14 h after status epilepticus).
- Analyzed DWI results visually and via apparent diffusion coefficient (ADC) maps.
Main Results:
- Significant postictal ADC decreases were observed in 1 out of 6 patients with TLE due to hippocampal sclerosis and single short seizures.
- One patient with a temporal lobe tumor showed ADC abnormalities.
- One patient in focal status epilepticus exhibited decreased ADC, while another with a continuous aura showed no DWI abnormality.
Conclusions:
- Postictal DWI can occasionally delineate epileptic areas in TLE patients.
- The diagnostic yield is low for hippocampal sclerosis with single short seizures but may be higher for tumors or status epilepticus.