Cortical Reorganization in Dual Innervation by Single Peripheral Nerve

Area of Science:

• Neuroscience
• Peripheral Nerve Injury and Repair
• Cortical Reorganization

Background:

• Functional recovery after peripheral nerve injury is linked to cortical reorganization.
• The mechanism by which a single donor nerve innervates dual targets remains poorly understood.

Purpose of the Study:

• To investigate cortical reorganization when the phrenic nerve is used to simultaneously innervate the diaphragm and the biceps muscle.
• To understand the brain's adaptation to dual target innervation following nerve transfer.

Main Methods:

• Rats with total brachial plexus (C5-T1) injury underwent phrenic nerve-musculocutaneous nerve transfer using end-to-side or end-to-end neurorrhaphy.
• Control groups included brachial plexus avulsion and sham surgery.
• Cortical representations of the diaphragm and reinnervated biceps were assessed using intracortical microstimulation at various time points post-surgery.

Main Results:

• Following injury, the motor representation of the injured forelimb disappeared.
• The diaphragm's cortical representation was preserved in the end-to-side group but lost in the end-to-end group.
• Biceps representation reappeared in both original biceps and diaphragm areas, eventually localizing to the original biceps area in the end-to-end group, while partially remaining in the diaphragm area in the end-to-side group by month 10.

Conclusions:

• The brain reorganizes biceps representation, shifting it from the original diaphragm area towards the original biceps area after phrenic nerve transfer.
• End-to-side phrenic nerve transfer allows partial preservation of reinnervated biceps representation within the original diaphragm cortical area.