Cerebral plasticity in crossed C7 grafts of the brachial plexus: an fMRI study.

In order to rescue elbow flexion after complete accidental avulsion of one brachial plexus, seven patients underwent a neurotization of the biceps with fibers from the contralateral C7 root. The C7 fibers used for the graft belonged to the pyramidal pathway, which descends from the cerebral hemisphere ipsilateral to the damaged plexus, and which controls extension and abduction of the contralateral arm. After several months of reeducation, a functional magentic resonance imaging study was performed with a 1.5 tesla clinical magnetic resonance scan system, in order to investigate the central neural networks involved in the recovery of elbow flexion. Functional brain images were acquired under four conditions: flexion of each of the two elbows, and imagined flexion of each elbow. Results show that flexion of the neurotized arm is associated with a bilateral network activity. The contralateral cortex originally involved in control of the rescued arm still participates in the elaboration and control of the task through the bilateral premotor and primary motor cortex. The location of the ipsilateral clusters in the primary motor, premotor, supplementary motor area, and posterior parietal areas is similar among patients. The location of contralateral activations within the same areas differs across patients.