By: Greg Vigna, MD, JD
Studies that measure the health-related quality of life (HRQoL) of tetraplegics when compared with paraplegic patients highlight the importance of specific functional abilities that relate directly to life satisfaction in the traumatic spinal cord injury (TSCI) population. In the TSCI population, loss of arm function, bowel/bladder function, and walking are the most important functions that contribute to reduced quality of life.[1] Independent mobility, the ability to transfer, has been shown to be the most crucial aspect to quality of life, followed by independence in self-care and sphincter management.[2] The goal of Improved upper-limb function after tetraplegia is the most important function for improving quality of life because not only do the arms need the same function, but they also provide function lost from impaired lower extremity function.[3]
Nerve Transfers:
Persons with midcervical cord complete or incomplete injuries will generally have sufficient nerve supply to the proximal muscles of the shoulder and biceps and sometimes the forearm to allow for voluntary muscle movement with force necessary to achieve functional movement and function use. Muscles that can generate sufficient force will, generally, as a rule, have sufficient motor nerve fiber density that allows for sufficient redundancy to allow for full strength contraction of the muscle, so that motor strength is not lost if the motor nerves to that muscle are spliced and grafted to nerves that have lost cortical input. In other words, you are grafting and splicing motor nerves that are above the level of the lesion to peripheral nerves under the level of the injury.
Zone of Preservation:
Injuries to the spinal cord cause damage to the neurological structures of the spinal cord at the level of the injury, causing a lower motor neuron injury at the level of the injury, which may also cause a lower motor injury above and below the level of the injury.. This issue creates uncertainty in clinical practice as to the viability of nerve transfers, because redundancy of peripheral motor nerves is not always the rule as sometimes function and strength can be reduced from a nerve transfer from the donor nerve when there isn’t sufficient redundancy within the nerve or muscles with similar function or sometimes the recipient muscle does not develop the desired level of innervation and strength or spasticity and contratures may limit function.
An expert in peripheral restorative neurosurgery is required, and the following spinal cord injury should be before nine months, as there may be nerve transfer options in the zone of preservation that are lost at one year because of atrophy. Consultation should include a review of the cervical MRI, a history and physical examination, and functional evaluation. Examination will include peripheral nerve electrical stimulation above, at the level, and below the level of the injury to determine suitability with nerve transfers. An EMG and nerve conduction is necessary to evaluate both the donor and recipient nerve and the muscles innervated by the nerves to understand redundancy for the donor nerve and the status of the recipient nerve and recipient muscle.[4] Adverse outcomes can occur, even with comprehensive evaluations by experienced peripheral nerve surgeons practicing neurorestorative surgery.
Tendon transfer surgery and nerve transfers are best evaluated simultaneously by a physician or as part of a multidisciplinary team with the expertise to provide both nerve transfers and tendon transfers, because the need for tendon transfers can be anticipated following nerve transfers to improve function. In addition, there are specific nerve transfers from a donor nerve that would preclude future tendon transfers.[5] The literature supports early nerve transfer surgery and then tendon transfers to maximise functional benefits. Patients who received nerve transfers on one side of their body and tendon transfers on the other side reported improved dexterity and appearance with nerve transfers and improved strength with tendon transfers, and would not choose to have two hands reconstructed the same way.[6] Tendon transfers have been the standard of care for restorative procedures in tetraplegics since the 1970s, with common tendon transfers to achieve elbow extension by deltoid to triceps or biceps to triceps transfers and tendon transfers to achieve wrist extension to allow for a tenodesis for grasp.[7]
Typical functions that may be restored include hand function and elbow extension.
Early consultation with a peripheral nerve restorative surgeon is desired before 9-months as there may be benefit to nerve transfers to muscles that are supplied within the preservation zone prior to the onset of denervation and may be an early nerve target for reinnervaton to attain elbow extension and thumb and finger extension for C6 injuries as axillary nerve transfers to the radial nerve to the elbow extensors reliably restores function with elbow extension and transfer of the radial branch to the supinator to the posterior internosseous nerve restores hand opening.[9]
Patient selection for nerve transfers are similar to that for tendon transfers in that individuals should not have any motor recovery for at least three months so that there is no risk of compromising natural recovery, motor strength of 5/5 for the supinator and biceps brachii are necessary to reduce the risk of donor deficits following restoration surgery, and no activity of the recipient muscles by physical examination and confirmed by EMG, and full passive range of motion of the joints. Following surgery, there are 2-3 weeks of splinting to protect the nerve coaptation sites, and then therapy initially tailored for donor movement paired with recipient movements and then strengthening over a period of three to six months.[10]
Outcomes described for the restoration of function in cervical spinal cord injury have been described as “promising” with extensor reinnervation of the wrist and finger and elbow extension more consistent with meaningful recovery than flexor reinnervation.[11]
Outcomes for cervical spinal cord injury with nerve transfers for achieving a Medical Research Council grade of at least ⅗ with elbow extension were 70% of patients, 79% hands gained at least ⅗ for finger extension, and at least ⅖ with finger flexors, and 52% of hands gained at least ⅗ or higher strength with finger flexion. Other outcomes were favorable using other measures of upper extremity function, and nerve transfers are promising and feasible in subacute and chronic spinal cord injury.[12] Complications, including infections and hematomas, are rare. Transient weakness of the wrist extension is anticipated following retraction of the wrist extensor muscles during transfers, and separation of the coaptation site with direct brachialis nerve to the anterior osseous nerve is a concern; bracing is required with strict compliance. Occupational therapy is essential.[13]
[1] Lo et al. Functional Priorities in Persons with Spinal Cord Injury: Using Experiments to Determine Preferences. Journal of Neurotrauma. April 2016.
[2] Goulet, et. al. Relationship Between Specific Functional Abilities and Health-Related Quality of Life in Chronic Traumatic Spinal Cord Injury. Am J Phys Med Rehabil 2019,98;14-19.
[3] Kalsi-Ryan, Ph.D, MSc, BSc, PT et al. A Synthesis of Best Evidence for the Restoration of Upper-Extremity Function in People with Tetraplegia. Physiotherapy Canada 2011; 63(4);474-89.
[4] Mandeville, Justin Brown, et al. A Neurophysiological approach to nerve transfers to restore upper limb function in cervical spinal cord injury. Neurosurg Focus 43(1):E6, 2017.
[5] Fox, et al. Nerve and Tendon Transfer Surgery in Cervical Spinal Cord Injury: Individualized Choices to Optimize Function. Top Spinal Cord Inj Rehabil 2018;24(3):275-287.
[6] Van Zyl, Hill, et al. Expanding traditional tendon-based techniques with nerve transfers for the restoration of upper limb function in tetraplegia: a prospective case series. The Lancet. Vol 394. /a/ugust 17, 2019
[7] Dunn, Ph.D. Tendon Transfers Surgery for People with Tetraplegia: An Overview. Archives of Physical Medicine and Rehabilitation.2016;97(6 Suppl 2):S75-80
[8] Hawasli, et al. Transfer of the nerve to the Brachialis to the Anterior Interosseous Nerve as a Treatment Strategy for Cervical Spinal Cord Injury: Technical Note. Global Spine Journal. December 15, 2014.
[9] Bertelli, M.D., Ph.D, et al. Nerve transfers for elbow and finger extension reconstruction in midcervical spinal cord injuries. J. Neurosurg Vol. 122, January 2015.
[10] Hahn, et al. Rehabilitation of Supinator Nerve to Posterior Interosseous Nerve Transfer in Individuals with Tetraplegia. Archives of Physical Medicine and Rehabilitation. 2016:97(6 Suppl 2):S160-8.
[11] Khalifeh, et al. Nerve Transfers in the Upper Extremity Following Cervical Spinal Cord Injury. Part 1: Systematic review of the literature. J Neurosurg Spine July 12, 2019; Khalifeh, et al. Nerve Transfers in the Upper Extremity Following Cervical Spinal Cord Injury. Part 2: Preliminary results of a prospective clinical trial. J Neurosurg Spine July 12, 2019;
[12] Javeed, et al. Upper Limb Nerve Transfer Surgery in a Patient with Tetraplegia. JAMA Network Open. 2022;5(11):e2243890.
[13] Bazarek, Justin Brown, et al. Nerve Transfers for Cervical Spinal Cord Injury. Nerves: Anatomy, Exposures, and Techniques. Hanna.
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