Functional connectivity of the transected brachial plexus after intercostal neurotization in monkeys

Abstract

Microsurgical reconstructions of brachial plexuses were performed on twelve monkeys by using ipsilateral intercostal nerves (T3-9). Reinnervation in individual nerves was evaluated monthly by observations of neuromuscular and electromyographic improvements. The electromyographic studies revealed reappearance of motor unit potentials. According to a motor scale ranging from 0 to 4, the mean muscle power 6 months after operation improved to 2.75 in the deltoid muscles, 2 in the biceps muscles, 1.22 in the triceps muscles, 1.13 in the flexor carpi radialis muscles, and 1.6 in the intrinsic muscles of the hands. Retrograde transport of horseradish peroxidase (HRP) from the neuromuscular junctions of the reconstructed musculocutaneous nerves 6 months after complete brachial plexus lesion in four animals demonstrated HRP-labeled neurons in the anterior horns, spinal ganglia and sympathetic ganglia of the thoracic spinal cords. It suggested that the regenerated afferent and efferent circuits in the thoracic cords innervating the transected brachial plexuses were able to generate the movements in the paralyzed upper limbs. However, as evidenced by the behavior patterns and the fact that retrograde-labeled neurons were all found in the thoracic cords, the novel movements observed in the reconstructed brachial plexuses were in synchrony with respiration. These results suggested that the plasticity of central neural networks is limited between two widely separated areas, such as between the midcervical and midthoracic motor cortical areas in the present studies, and therefore, the efforts to reconstruct neural networks, both centrally and peripherally, should aim at rebuilding situations as nearly to the original status as possible.

Cortical plasticity after brachial plexus injury and repair: a resting-state functional MRI study

“…After recovery, there is another reorganization, but the new map will not be the same as the original map because of peripheral mismatch in the regeneration of nerve fibers. 5,6,9,[13][14][15]18,19,30 Resting-state fMRI (rs-fMRI) is a novel method of examining the functional networks of the brain and is beneficial because it does not depend on task performances, it allows data to be easily acquired, and it enables the evaluation of functional networks. 2,7,32,38 Although task-based fMRI cannot be performed for patients with BPI because their affected limb is completely paralyzed, rs-fMRI analysis can be done without patients performing any task.…”

Functional magnetic resonance imaging and control over the biceps muscle after intercostal—musculocutaneous nerve transfer

“…Using retrograde nerve tracing, research in monkeys with ICN-MCN transfer has shown that this type of spinal plasticity does not occur. 3 The results of two studies in humans, in which transcervical and transthoracic magnetic stimulation was used after ICN-MCN transfer, confirm these findings. 13,14 From both studies it can be concluded that it is unlikely that novel neural connections are formed at a spinal level.…”

A novel strategy for repairing preganglionic cervical root avulsion in brachial plexus injury by sural nerve grafting

“…Any efforts to reconstruct central or peripheral neural networks must focus on rebuilding as close to the original anatomical structure as possible. 8 We took precisely this approach in our novel, 2-stage surgical strategy through direct reimplantation of root stumps or the use of nerve grafts to bridge the gap between the trunk level of the brachial plexus and the corresponding segments of the spinal cord at the injury site. Incorporating the use of fibrin glue containing aFGF as an adhesive and neurotrophic agent yielded relatively good preliminary results.…”