Cervical spinal cord injury (SCI) is a life altering and devastating injury. Some people with cervical SCI can lift and bend their arms but have very limited use of their hands. Improving hand function is rated as more important to patients then restoring other functions such as walking. This research investigates the novel application of a well-known technique—peripheral nerve transfer surgery—to restore hand function in people with cervical SCI.
Nerve transfers can be used to essentially rewire the system to make some muscles work again following SCI. The transfer is done in the arm and bypasses the damaged spinal cord to deliver a signal from the brain to a muscle that became disconnected following injury. A donor nerve is taken from a non-essential uninjured muscle and transferred to provide a more critical function. Because the nerve transfer procedure involves cutting and reattaching nerve tissue, time is required to regenerate working connections between the nerves and muscle and to allow the brain to relearn how to use and strengthen that muscle.
This work will bring together a multidisciplinary research team to perform an investigation of this surgery. Detailed assessment of patients who have already had the surgery will provide information on what makes a good candidate for the surgery. Rigorous study of a new group of patients will provide much needed information on even subtle positive or negative changes in function. Measurements of changes in quality of life and interviews of patients and caregivers will improve our understanding of the best way to use this surgical treatment.
This study will provide preliminary data that could lead to future studies at other SCI centers, to compare this technique to other treatments, and to expand the technique to improve other functions.
The nerve transfer bypasses the SCI to restore volitional control of hand function. In some patterns of SCI there are intact motor units just below the zone of injury. These motor units are comprised of the lower motor neuron cell body (located within the spinal cord), its axonal projection (which travels to make up part of the associated peripheral nerve) and the muscle end organ. Redundant functioning nerves (green) that are under volitional control are re-routed (yellow arrow) to the nerves that come off below the SCI (red). Because these nerves lie parallel to each other in the arm, it is possible to tap into a functional nerve and redirect the signal to the non-functioning neighbor.
The nerve transfer surgery necessarily creates a peripheral nerve injury to treat an irreparable central nervous system injury. The transferred nerve grows down the new path and time is required to reach the target muscle and complete the motor retraining and strengthening necessary to restore meaningful movement. This process can take months to years, however, during that time patients all pre-surgical activities. Unlike tendon transfer procedures, no splinting is required because the nerve coaptation is done under no tension and the endogenous musculotendinous unit is left in situ.
|This schematic reviews the commonly performed nerve transfer surgeries in this case series. All rely on the same principle of bypassing the injured metamere or zone of spinal cord injury. Expendable donor nerve branches under volitional control are coapted to non-functioning recipient nerves. To restore elbow extension, branches of the axillary nerve that supply the posterior head of the deltoid muscle may be transferred to branches of the radial nerve that supply the medial or other heads of the triceps musculature. To restore prehension the branches of the musculocutaneous nerve that supply the brachialis muscle can be coapted to branches of the median nerve (the anterior interosseous nerve) that supply the flexor pollicis longus and flexor digitorum profundus to the index and, sometimes, long finger. Extra branches may also be used to restore wrist flexion (flexor carpi radialis) or grasp (flexor digitorum superficialis). To restore wrist or finger extension nerve transfers can be performed between branches of the radial nerve that are under volitional control, such as the supinator, and branches that are not, such as the branch to the extensor carpi ulnaris or to extensor digitorum communis.|
This schematic depicts the idea of the ‘rescue’ phenomenon. In some cases of spinal cord injury with a more extensive zone of injury, once return of upper extremity function and the overall medical condition has stabilized, it might be reasonable to consider relatively early intervention with nerve transfer.
This is in contrast to a patient with a narrow zone of injury (example, C7 only) who still may be a candidate to restore function to nerves and muscles by restoring volitional function to the C8/T1 nerve fibers even years after the SCI. With a narrow zone of injury, the motor units below the level of injury are still in continuity and that muscle tissue is preserved.
The patient with a more extensive zone of injury as depicted in this figure would not be a candidate for delayed/late nerve transfer. This is because that muscle tissue does not have an intact motor neuron cell body and would undergo terminal atrophy in 12-18 months post-injury, as is seen in peripheral nerve injury.
Cervical level spinal cord injury can significantly affect hand function. Depending on the level and type of injury, surgery to improve hand and arm function may be an option. Surgical treatment may include nerve transfers or other procedures.
This surgery can only benefit patients with specific types of spinal cord injury. To be eligible, a patient must have quadriplegia with a motor level C6 or C7 spinal cord injury. Because the procedure relies on working nerves above the C6 and C7 level, it will not benefit patients with C1 through C5 level injuries. The goal of the procedure is to restore the ability to pinch the thumb and index finger.
If you think you are a candidate for nerve transfer for a motor level C6 or C7 spinal cord injury, please begin by contacting your personal physician.
Below are links to the documents with more information about this surgery. Please review this information carefully with your primary care or rehabilitation physician to see if he or she thinks you may be a candidate.
If your primary care or rehabilitation physician thinks a referral is appropriate, he or she should send the information specified in the patient letter below.