E09 Iron Content In The Corpus Callosum In Huntington’s Disease

Background Higher iron concentration in subcortical grey matter structures is documented in Huntington’s disease (HD) but the disease effects on white matter (WM) is less well documented. We have previously reported macro and microstructural alterations in the corpus callosum (CC) in HD. Aims To investigate the regional iron content in the CC using the Transverse Relations Rate (T2*) and DTI tractography. We examined the CC in its entirety and segmented into its seven anatomical sub regions: the orbital frontal (OF), anterior frontal (AF), superior frontal (SF), superior parietal (SP), posterior parietal (PP), temporal (Temp), and occipital (Occ). Methods Subjects groups included 25 HD patients, 25 presymptomatic HD (PreHD) subjects, 40 healthy controls. Six consecutive T2*-weighted gradient echo-planar whole-brain volumes were acquired at different time of echo. Tractography was performed for each region of the CC by manually drawing two regions of interest on each individuals fractional anisotropy colour map. To test for callosal differences, a Mancova was applied covering for gender and age. Results We found reduced iron content in HD patients across the CC as a whole. Regional results revealed increased iron in the Occ, SP, and OF tracts of Pre-HD subjects when compared with HD patients and decreased iron in the Occ tract of HD patients when compared with controls as well as increased iron in the OF of Pre-HD subjects compared to controls. Conclusion An increase of iron content has been suggested to be associated with remyelination process in attempting to repair myelin damage. Our results are in agreement with this hypothesis and suggest an attemp to repair myelin in the posterior callosal fibre (the Occ) and motor fibres (SP) in presymptomatic stage of HD (higher iron content). This process eventually fails, with the pathology progression, as indicate by lower content of iron in HD.