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Diffusion mapping applied to mesial temporal lobe epilepsy: preliminary observations
J W Hugg1, E J Butterworth, R I Kuzniecky
1UAB Epilepsy Center and Center for Nuclear Imaging Research, Department of Neurology, University of Alabama at Birmingham, 35294-0021, USA.
Objective:
To evaluate whether diffusion mapping could lateralize intractable seizures in mesial temporal lobe epilepsy (MTLE) patients.
Background:
Animal seizure models show acute postictal depression of the apparent diffusion coefficient of water (ADCw), interictal normalization, then chronic elevation.
Methods:
The hippocampal plane was imaged with five diffusion weightings along each axis. Three orthogonal ADCw maps were averaged to produce an isotropic ADCw map.
Results:
In all eight MTLE patients, ADCw was elevated by a mean of 10+/-3% (p<0.01, paired t-test) interictally in the ipsilateral hippocampus, where side of seizure focus was determined electrographically with corroboration by volumetric MRI studies. Measured ADCw values in phantoms and five normal brains agree with published values.
Conclusions:
Brain tissue with interictally increased ADCw may represent an epileptogenic region with neuronal loss, gliosis, and expanded extracellular space (hippocampal sclerosis). Thus, diffusion mapping may confirm seizure lateralization.
Insights
Diffusion mapping can identify the seizure focus in patients with mesial temporal lobe epilepsy (MTLE). Elevated apparent diffusion coefficient of water (ADCw) in the hippocampus suggests an epileptogenic region, aiding in seizure lateralization.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Diffusion MRI
Background:
- Animal models indicate altered water diffusion post-seizure.
- Apparent diffusion coefficient of water (ADCw) changes acutely, normalizes, then elevates chronically.
- Interictal elevation of ADCw is observed in chronic seizure models.
Purpose of the Study:
- To determine if diffusion mapping can lateralize intractable seizures in mesial temporal lobe epilepsy (MTLE) patients.
- To investigate the utility of apparent diffusion coefficient of water (ADCw) mapping for seizure focus identification.
Main Methods:
- Utilized diffusion mapping with five diffusion weightings along each axis.
- Generated isotropic ADCw maps by averaging three orthogonal ADCw maps.
- Corroborated seizure focus lateralization with electrography and volumetric MRI.
Main Results:
- Interictal elevation of ADCw (mean 10+/-3%, p<0.01) was observed in the ipsilateral hippocampus of all eight MTLE patients.
- ADCw values in phantoms and normal brains aligned with published data.
- Demonstrated a statistically significant increase in ADCw in the epileptic hippocampus.
Conclusions:
- Interictally increased ADCw may indicate an epileptogenic zone characterized by neuronal loss and gliosis (hippocampal sclerosis).
- Diffusion mapping shows promise in confirming seizure lateralization in MTLE.
- This technique could improve the localization of seizure foci for surgical planning.