Reduced functional connectivity within the primary motor cortex of patients with brachial plexus injury

TL;DR

This study investigates how traumatic brachial plexus injury affects the organization of the primary motor cortex, revealing reduced functional connectivity in the arm region without gray matter loss, indicating altered neural activity.

Contribution

It demonstrates that BPA leads to decreased functional connectivity in M1's arm area, independent of gray matter density, highlighting specific neural reorganization after injury.

Findings

Faster decay of functional correlations in M1 arm region of BPA patients

No difference in gray matter density between BPA patients and controls

Reduced activity in horizontal connections responsible for upper limb motor synergies

Abstract

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.