Cortical plasticity and nerve regeneration after peripheral nerve injury

Abstract

With the development of neuroscience, substantial advances have been achieved in peripheral nerve regeneration over the past decades. However, peripheral nerve injury remains a critical public health problem because of the subsequent impairment or absence of sensorimotor function. Uncomfortable complications of peripheral nerve injury, such as chronic pain, can also cause problems for families and society. A number of studies have demonstrated that the proper functioning of the nervous system depends not only on a complete connection from the central nervous system to the surrounding targets at an anatomical level, but also on the continuous bilateral communication between the two. After peripheral nerve injury, the interruption of afferent and efferent signals can cause complex pathophysiological changes, including neurochemical alterations, modifications in the adaptability of excitatory and inhibitory neurons, and the reorganization of somatosensory and motor regions. This review discusses the close relationship between the cerebral cortex and peripheral nerves. We also focus on common therapies for peripheral nerve injury and summarize their potential mechanisms in relation to cortical plasticity. It has been suggested that cortical plasticity may be important for improving functional recovery after peripheral nerve damage. Further understanding of the potential common mechanisms between cortical reorganization and nerve injury will help to elucidate the pathophysiological processes of nerve injury, and may allow for the reduction of adverse consequences during peripheral nerve injury recovery. We also review the role that regulating reorganization mechanisms plays in functional recovery, and conclude with a suggestion to target cortical plasticity along with therapeutic interventions to promote peripheral nerve injury recovery.

Keywords: cortical plasticity; injury; mechanisms; nerve transfer; neurorrhaphy; peripheral nerve; phantom limb pain; recovery; regeneration; treatment.

Figure 1

Sunderland’s classification of nerve injuries. Grade 1: The continuity of nerve fibers remains intact, without Wallerian degeneration. Grade 2: The continuity of the axon and its myelin sheath is interrupted. The endoneurial tube remains intact, and the distal end of the injured nerve shows Wallerian degeneration. Grade 3: Nerve fibers (including axons and the endoneurium) are interrupted. The perineurium remains intact. The distal end of the injured nerve shows Wallerian degeneration. The possibility of self-recovery remains. Grade 4: Only the epineurium remains intact. The distal end of the injured nerve shows Wallerian degeneration. Grade 5: The entire nerve is completely interrupted. The distal end of the injured nerve shows Wallerian degeneration. Figure 1 was created with BioRender. com.

Figure 2

Schematic of the interactions between cortical plasticity and peripheral nerve injury. Injuries to the peripheral nerve can cause the interruption of signal transmission. The cerebral cortex then undergoes reorganization because of the signal transmission disorder. Regulating the reorganization of the brain affects both the recovery of peripheral nerves and the sensorimotor functions of corresponding target organs.