Nerve Transfer

In some cases, we may use a nearby relatively expendable nerve or fascicle of a nerve and transfer it to a nerve that is not functioning. This is often done downstream from a level of injury. The main advantage to performing a nerve transfer is it brings healthy donor axons closer to the target thereby allowing for earlier reinnervation and minimize atrophy of the neuromuscular junction and muscle. Nerve transfers are mainly performed to restore motor function, however, there are transfers described to restore sensation primarily in the hand and are less commonly used. The donor nerve used for transfer is carefully selected such that little to no dysfunction is realized in its absence (when it is sacrificed and re-purposed).

An example of a nerve transfer is when a fascicle from the ulnar nerve that supplies partial innervation to wrist flexion is used to transfer to a fascicle for the biceps muscle to restore elbow function.

After nerve transfer, the nerve still has to regrow beyond the repair site and it takes several months to years for these functions to return. Therefore, we generally aim to intervene with nerve transfer by six months or sooner. As with any type of nerve repair, the strength recovered is never the same as it was before the injury, however, the goal is often to regain a motion to move against the force of gravity or more in some cases. In addition, after nerve transfer, relearning and physiotherapy is required to train your brain the repurposed function of the donor nerve.

In general, there are two types of nerve transfers, described below.

End-to-end transfer

This type of transfer occurs when the donor nerve and recipient nerve are cut and sewn together directly similar to a direct repair described above. This is done when we do not anticipate any upstream recovery to the recipient nerve or when the affected nerve is completely impaired. An example of an end to end nerve transfer is that described above to restore elbow flexion.

Reverse end-to-side or “supercharged” nerve transfer

This type of nerve transfer is performed when there may be some upstream recovery  in the future or only partial dysfunction of the recipient nerve and you do not want to complete cut it/downgrade its function to perform the transfer. In this case, the donor nerve is cut and the end of it sewn into the side of the recipient nerve, thereby allowing for some potential upstream recovery yet providing new support to the dysfunctional nerve.

An example of this type of nerve transfer is when the downstream anterior interosseous nerve is sutured into the side of the motor component of the ulnar nerve to restore muscles in the hand when there is a severe compression or injury to the ulnar nerve at level of elbow or above.

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Summary for patients

1. Nerve transfers involve moving a functioning nerve above your level of injury and “plugging” it into a muscle that is not working below your level of injury to restore some function in the recipient muscle.
2. The donor nerve is is taken from a muscle that is working well and is strong. This donor nerve is cut and connected into a muscle that is not functioning as a result of the patient’s spinal cord injury. The muscle that the donor nerve is being “plugged” into is called the recipient muscle.
3. Possible functions/movements that can potentially be restored with nerve transfer procedures are: arm straightening (elbow extension), wrist extension, hand opening (finger extension), and hand closing (pincer grip).
4. Nerve transfer operations have very little post-op recovery (or healing time), but it takes a long time to see any new movement as nerves grow slowly (a millimeter a day or an inch a month). New movement is often not seen until 6-12 months following the surgery. Movement typically starts with small flickers, and progresses to larger movements over a period of 1 to 2 years.
5. Your participation in daily stretches, wearing splints as prescribed, visualization exercises, and time spent learning and strengthening your operated arm and hand is critical to success. The pre-surgery and post-surgery stages of rehabilitation and recovery for nerve transfers are outlined below, however your therapy needs will be customized by your rehabilitation team.
6. Risks of surgery, side effects and adverse effects are detailed in the pre-surgery planning section.

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