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

Abstract

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.

Reorganization in motor cortex after brachial plexus avulsion injury and repair with the contralateral C7 root transfer in rats

“…18,[31][32][33][34][35][36][37] Clinically, an fMRI study on neurotization of the biceps with the contralateral C7 root showed that flexion of the neurotized arm was associated with a bilateral network activity. 18 The contralateral cortex that originally involved in control of the repaired arm still participated in the elaboration and control of the task through the bilateral premotor and primary motor cortex. 18 In this study, we transferred the contralateral C7 root to the median nerve to restore the function of forepaw flexion in rats.…”

“…18 The contralateral cortex that originally involved in control of the repaired arm still participated in the elaboration and control of the task through the bilateral premotor and primary motor cortex. 18 In this study, we transferred the contralateral C7 root to the median nerve to restore the function of forepaw flexion in rats. The results showed that the injured forepaw representation area was found in the ipsilateral motor cortex 5 months after the nerve transfer of contralateral C7 root, which proved that both the left injured limb and the right healthy limb were controlled by the left motor cortex simultaneously.…”

“…15,[18][19][20] The patients were found using the same primary motor cortex with trunk movements to lead contraction of the biceps muscle reinnervated by the intercostal nerve, which implies that functional plasticity may occur in the patients using the primary trunk motor cortex for elbow flexion. 21 Further investigations of roles of cortical reorganization in peripheral nerve injuries would provide evidences for development of therapeutic strategies for modulating central nervous system reorganization, amplifying positive adaptive changes for improvement of functional recovery, and diminishing undesirable consequences, besides enhancing axonal regeneration and promoting selective target reinnervation.…”

Current concepts in plasticity and nerve transfers: relationship between surgical techniques and outcomes

“…4 The original motor area for flexion of the arm is still involved but in concert with the ipsilateral cortex, which normally is not the case (Fig. 6).…”

Técnicas de reconstrucción nerviosa en cirugía del plexo braquial traumatizado (Parte 1): Transferencias nerviosas extraplexuales

“…Al igual que el "brazo que respira" descrito para el nervio frénico, el movimiento sincrónico del lado sano es necesario típicamente al comienzo del proceso de reinervación para obtener una contracción muscular en el lado afectado. Más tarde, como regla general, se consigue un control mayor, aunque no totalmente independiente 4 . Estos resultados limitados, junto con el bajo, aunque no inexistente riesgo de déficit sensitivo o motor (lo que no es un problema menor en el contexto de un paciente con una sola extremidad superior normal), el mencionado fenómeno de cocontracción del brazo sano, y la complejidad técnica de este procedimiento, se opuso a su uso generalizado y su indicación queda limitada a ciertos pacientes muy seleccionados con lesiones concomitantes de nervio frénico y espinal accesorio.…”