Schweizer Archiv für Neurologie und Psychiatrie ... - Sanp.ch

Posters SSNR
3]. The aim of this study is to assess the reversibility of these
diffusion changes following temporal lobe surgery, by applying
a novel voxel-based tract-based spatial statistics (TBSS) [4]
technique for whole-brain analysis of fractional anisotropy (FA).
Material and methods: The study included 23 patients with
unilateral HS. Twelve patients underwent temporal lobe surgery.
Follow-up MRI was done in a mean interval of 4 months. Preprocessing
and statistics analysis of FA maps with TBSS was
done using FSL tools [5]. Pre-operative FA asymmetry in all 23
patients was assessed within subjects between lesional and
contralateral hemispheres with TBSS with threshold-free cluster
enhancement (TFCE)[6] correction. The post-operative dataset
of 12 patients was compared with the corresponding preoperative
dataset using voxel-wise and volume of interest (VOI)
statistical analysis with a paired t-test.
Results: Within a mean interval time of 6.3 months after surgery,
the majority of the included patients was seizure free (n = 10,
83.3%). The pre-operative comparison between lesional and
contralateral hemispheres showed a significant FA reduction in
the ipsilateral hippocampus, fornix and corpus callosum. Voxelwise
comparison between post and pre-operative dataset did
not show supra-threshold voxels. VOI statistical analysis showed
significant FA decrease in ipsilateral fornix and significant
increase in contralateral fornix and bilateral white matter after
surgery.
Conclusion: The ipsi-lesional fornix showed decreased
FA after surgery, consistent with Wallerian degeneration. In
contrast, contra-lesional fornix and bilateral large white matter
fiber tracts demonstrated increasing FA indicating recovery of
axonal integrity. This might be due to the removal of spreading
epileptogenic activity after temporal lobe surgery. References:
1. Assaf B, Mohamed F, Abou-Khaled K, et al. Diffusion Tensor
Imaging of the Hippocampal Formation in Temporal Lobe
Epilepsy. AJNR. 2003;24:1857–62. 2. Concha L, Beaulieu C,
Gross D. Bilateral limbic diffusion abnormalities in unilateral
temporal lobe epilepsy. Ann Neurology. 2004;57:188–96.
3. Thivard L, Lehéricy S, Krainik A, et al. Diffusion tensor
imaging in medial temporal lobe epilepsy with hippocampal
sclerosis. NeuroImage. 2005;28:682–90. 4. Smith S, Jenkinson
M, Johansen-Berg H, et al. Tract-based spatial statistics:
Voxelwise analysis of multi-subject diffusion data. NeuroImage.
2006;31:1487–505. 5. Smith S, Jenkinson M, Woolrich M, et al.
Advances in functional and structural MR image analysis and
implementation as FSL. NeuroImage. 2004;23:208–19. 6. Smith
S, Nichols T. Threshold-free cluster enhancement: Addressing
problems of smoothing, threshold dependance and localisation in
cluster inference. NeuroImage. 2009;1:83–98.
Results: Different characteristics of the atherosclerotic lesions
are presented in table 1. Echogenicity was significantly
correlated with the grade of neovascularization (p = 0.002). More
echolucent plaques had higher degree of neovascularization
compared with more echogenic ones (figure 1A). Lesion severity
assessed by degree of stenosis and maximal thickness was
significantly associated with grade of neovascularization (p