  This study aims at the effects of traumatic brachial plexus lesion with root
avulsions (BPA) upon the organization of the primary motor cortex (M1). Nine
right-handed patients with a right BPA in whom an intercostal to
musculocutaneous (ICN-MC) nerve transfer was performed had post-operative
resting state fRMI scanning. The analysis of empirical functional correlations
between neighboring voxels revealed faster decay as a function of distance in
the M1 region corresponding to the arm in BPA patients as compared to the
control group. No differences between the two groups were found in the face
area. We also investigated whether such larger decay in patients could be
attributed to a gray matter diminution in M1. Structural imaging analysis
showed no difference in gray matter density between groups. Our findings
suggest that the faster decay in neighboring functional correlations without
any gray matter diminution in BPA patients could be related to a reduced
activity in intrinsic horizontal connections in M1 responsible by upper limb
motor synergies.
