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Nerve transfer for spinal cord injuries


Introduction

  • Given the success of nerve transfers for the treatment of brachial plexus and peripheral nerve injuries, many surgeons also use this form of treatment to circumvent the damaged areas of the spinal cord and reestablish essential motor function ( Table 76.1 ). Nerve transfers can be performed together with tendon transfers or as the primary treatment for spinal cord injury (SCI) patients in some cases.

    TABLE 76.1
    Common Nerve Transfers for Functional Deficits in Spinal Cord Patients
    Functional Deficit Nerve Transfer
    Elbow extension Posterior deltoid nerve branch to triceps nerve branch
    Wrist extension Brachialis nerve to extensor carpi radialis nerve
    Finger extension Supinator motor branch to posterior interosseous nerve
    Thumb and index flexion Brachialis nerve to anterior interosseous nerve

  • Benefits of nerve transfer:

    • 1.

      An expendable nerve can be used to power an essential function by reinnervating one or several muscles.

    • 2.

      Patients remain immobilized for less time postoperatively compared with tendon transfers. They are also less likely to have pain and scarring.

    • 3.

      The donor nerve can be partially spared to maintain some function to native muscle.

    • 4.

      Unlike tendon transfers, tensioning and proper line of pull do not need to be considered for nerve transfers.

  • Drawbacks of nerve transfer:

    • 1.

      Time to reinnervation varies among SCI patients.

    • 2.

      If the donor nerve is weaker than expected (i.e., Medical Research Council [MRC] < 3), then reinnervation is poor.

Indications

  • Patients are observed for spontaneous recovery for 6 to 12 months before they are considered for nerve transfer; it is assumed that paralyzed muscles are unlikely to recover after 6 months.

  • SCIs affect the upper motor neurons and are heterogeneous in presentation. Therefore the recipient muscles continue to receive input from the lower motor neurons (LMNs) long after injury. Patients with upper nerve injuries remain primed for reinnervation longer than brachial plexus and peripheral nerve injury patients, who require nerve transfer within 1 year of injury.

  • Some spinal cord injury patients have both upper motor neuron (UMN) and LMN injuries; these patients require nerve transfer within 1 year of injury (so the muscle is still receptive).

  • A donor nerve must be available in close proximity to the recipient nerve for direct coaptation.

Contraindications

  • Patients with some type of LMN injury are not eligible for nerve transfers more than 1 year after the injury.

  • In line with the considerations for tendon transfers, nerve transfers cannot be performed in patients who have significant comorbidities that preclude general anesthesia. Patients also require adequate psychosocial support and should have realistic expectations regarding their potential functional gains.

  • Patients with chronic pain or inadequate donors are also not candidates for surgery.

Clinical examination

  • An organized examination of the entire upper extremity is performed. See Chapter 69 Tendon and Nerve Transfer for Spinal Cord Injury for details.

  • Assess the upper extremity for motor deficits and potential donor nerves. Grade the donors using the MRC scale (see Table 69.1 ). Assess muscle tone, bulk, and potentially deep tendon reflexes.

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