Exploring white matter tracts in band heterotopia using diffusion tractography.
Band heterotopia is a malformation of cortical development characterized by bands of gray matter in the white matter parallel to the surface of the neocortex. Histopathological studies have suggested that small white matter tracts pass through the heterotopia, and functional magnetic resonance imaging studies have shown activation in the malformation. We used diffusion tractography to explore the anatomical connectivity of band heterotopia and, in particular, whether in vivo white matter tracts traverse the heterotopic gray matter. Five patients with band heterotopia and five control subjects were scanned with whole brain diffusion tensor imaging. Anisotropy maps were calculated. Using fast marching tractography, we produced maps of connectivity and tract traces from two seed points, in the splenium of the corpus callosum and the right parietal lobe. Eigenvectors were found to pass through the band heterotopia in an aligned fashion. Patterns for maps of connectivity were similar in patients and control subjects. Areas of high connectivity were found in the band heterotopia and in cortical areas on the far side of the malformation from the seed point. The tracts hence appeared to traverse or end within the band heterotopia. The results are in agreement with previous histopathological studies and indicate the structural basis of the functional connectivity and absence of focal deficits in these patients.
MRI Unit, National Society for Epilepsy, Department of Clinical and Experimental Epilepsy, National Hospital for Neurology and Neurosurgery, Institute of Neurology, University College London, London, United Kingdom.
Sofia H
SH
Eriksson
Mark R
MR
Symms
Fergus J
FJ
Rugg-Gunn
Philip A
PA
Boulby
Claudia A M
CA
Wheeler-Kingshott
Gareth J
GJ
Barker
John S
JS
Duncan
Geoffrey J M
GJ
Parker
D000328:Adult; D061085:Agenesis of Corpus Callosum; D016880:Anisotropy; D001931:Brain Mapping / Q000379:methods; D002828:Choristoma / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009434:Neural Pathways / Q000002:abnormalities*; D010296:Parietal Lobe / Q000002:abnormalities*