Sensorimotor cortical changes assessed with resting-state fMRI following total brachial plexus root avulsion.

OBJECTIVE: Peripheral nerve injury can induce immediate and long-standing remodelling of the brain cortex, which may affect outcomes of nerve repair. This study examined changes of corresponding cortical representations in patients with brachial plexus injuries.
METHODS: Resting-state fMRI was acquired for 13 adult patients with total brachial plexus root avulsion, three of whom underwent second scans 7 or 8 months later. The time of examination ranged from 1 to 16 months after injuries. Nine healthy adults were enrolled as control. Seed-based functional connectivity was performed for all subjects.
RESULTS: For nine patients whose first fMRI was performed from 1 to 4 months after brachial plexus injuries, images showed that their cortical maps of sensorimotor areas corresponding to the hand and arm in the hemisphere contralateral to the injured side had much weaker correlation with the supplementary motor area (SMA) than those ipsilateral to the injured side. Symmetrical maps of bilateral cortical sensorimotor areas corresponding to the hand and arm were observed in other four cases with fMRI tested from 7 to 16 months after injuries. For three of the nine patients with asymmetrical cortical representations, second scans indicated symmetric results or even stronger correlation with SMA in the cerebral cortex contralateral to the injured side.
CONCLUSIONS: Total brachial plexus root avulsion causes cortical representations of the brachial plexus to undergo a change from an inactive to an active state. This implies that peripheral deafferentation after brachial plexus injuries will induce corresponding cortical representations to be occupied by adjacent non-deafferented cortical territories.