POSTICTAL DIFFUSION TENSOR IMAGING
Abstract number :
B.04
Submission category :
Year :
2003
Submission ID :
3589
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Beate Diehl, Mark R. Symms, Philip A. Boulby, Tuuli Salmenpera, Claudia A.M. Wheeler-Kingshott, Gareth J. Barker, John S. Duncan MRI Unit, Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United
To evaluate postictal diffusion tensor imaging (DTI) as a tool to delineate the zone of seizure onset.
DTI and statistical parametric mapping (SPM) were used to examine objectively the diffusion properties of 20 patients with intractable epilepsy (18 with focal epilepsy, 2 with generalized epilepsy) both postictally and interictally and to compare them with 27 normal controls who were scanned twice. Scans were obtained as soon as possible after a seizure and again after a seizure free interval greater than 24 hours in 10 patients and 2 to 18 hours in the other patients. Three sets of statistical tests were performed on each patient[rsquo]s fractional anisotropy and mean diffusivity scans: inter-ictal versus controls, post-ictal versus controls, and a third [ldquo]difference analysis[rdquo] to test for significant changes in diffusion between postictal and interictal scans in comparison with the differences noted in the two sets of control scans.
Compared to the control group, thirteen of the 20 patients (72% of the patients with focal epilepsy) had increases in mean diffusivity in the interictal scan compared to a single set of control scans. No decreases in mean diffusivity compared to the controls were detected. The differential analysis detected relative decreases in mean diffusivity postictally in 9 patients (50% of the patients with focal epilepsy). These changes were focal in seven patients. In six of those the side of the epileptic focus was known and colocalization was present in three. No changes in anisotropy were noted between the post- and interictal states.
This study showed that diffusivity is frequently abnormally increased in patients with focal epilepsy and that postictally a significant proportion of patients show a relative decrease in diffusivity, probably reflecting cellular swelling in the area of seizure onset and possibly also in areas of spread. Postictal diffusion changes however appear complex and dynamic and timing after the seizure may be critical. Anisotropy measures appear to be less sensitive to those changes. Further systematic studies are needed and correlation with outcome after epilepsy surgery will determine the role of the postictal diffusivity measures in the presurgical evaluation of epilepsy patients.
[Supported by: Action Medical Research, UK.]