Background The spatial pattern of atrophy of a disease is related to its functional connectivity structure, mapped by resting-state fMRI. In Huntington disease (HD), the striatum is the most vulnerable brain structure, linked to specific frontal areas and thalamus by five parallel frontal-subcortical circuits. Motor (MN) and Default Mode (DMN) resting-state networks play a key role in HD.
Aims We hypothesise that the striatum-related MN could be damaged in HD; while the DMN, not involving the striatum, could be instead relatively preserved. Therefore, we investigated these two networks and related them to grey matter loss.
Methods Ten patientsand 10 controls underwent T1-weighted imaging (MDEFT sequence) and resting-state fMRI (gradient echo-EPI sequence: TR/TE=65/30 ms, voxel-size=2.5 mm3; 400 volumes) on a 3T Siemens scan. We computed the seed-based functional connectivity patterns from two seeds: the Posterior Cingulate cortex (PCC) and the Supplementary Motor area (SMA), considered cortical hubs of the DMN and the MN, respectively. We also analysed different grey matter loss areas in patients and controls by FSL-VBM.
Results Patients showed grey matter loss in all cortical and subcortical areas involved in MN, with preservation of SMA, in spite of structural preservation of all the cortical areas involved in the DMN. Coherently, we found functional connectivity impairment in MN, with loss of connexions of SMA with primary and secondary sensory-motor areas and putamen and relatively preserved connexions in the DMN.
Conclusions The striatum–related MN, but not the DMN, is impaired in HD. Even if all MN regions showed grey matter volume loss, SMA remains structurally and functionally preserved, at least at early HD stages. This might be linked to the central role of SMA, which allows the MN to integrate with other functional circuits. Thus, these results seem to suggest a pattern of damage from local to more central nodes.
- brain volume
- resting state
- Huntington Disease