Postictal diffusion weighted imaging.
OBJECTIVE
Our aim was to determine whether diffusion weighted imaging can detect abnormalities of diffusivity after single seizures, and investigate the localisation and time course of any changes.


METHODS
Twenty-one patients with intractable focal epilepsy were imaged interictally and after 23 seizures. Voxel-based statistical parametric mapping was used to detect postictal changes in mean diffusivity (MD), compared to the changes noted in 20 controls scanned twice. The time course and magnitude of the changes were evaluated by measuring MD in the areas of change identified by the voxel-based analysis.


RESULTS
Thirty-four focal changes in MD (24 decreases, 10 increases) were detected after 12 of 23 seizures in 11 patients, after a median interval of 53 min from the time of seizure onset. Five patients had areas of both increased and decreased diffusion after seizures. In four patients, postictal changes in diffusion corresponded with the presumed seizure focus. Repeated postictal scanning, after a further interval of a median of 46 min in eight patients, showed that postictal changes in MD, both increases and decreases, were returning towards interictal values.


CONCLUSIONS
Diffusion weighted imaging identified focal changes in MD after 52% of single complex partial and secondarily generalised seizures. Changes in MD corresponded to the putative seizure focus in a minority of cases suggesting that the technique is not promising as a method for localising seizure foci, but may indicate the networks involved in seizures.
Salmenpera
Tuuli M
TM
The MRI Unit, The National Society for Epilepsy and the Department of Clinical and Experimental Epilepsy, Institute of Neurology, Queen Square, University College London, London, UK.
Symms
Mark R
MR
Boulby
Philip A
PA
Barker
Gareth J
GJ
Duncan
John S
JS
D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012640:Seizures / Q000175:diagnosis / Q000503:physiopathology*; D013997:Time Factors