NERVE TRANSFER (Basic idea and types of nerve transfer)

Here's the basic idea and types of nerve transfer.
1. Introduction
2. Nerve Degeneration and
Regeneration
3. In the cases of unsuccessful
Regeneration
4. Indications
5. Contraindications
6. Ideal Donor nerve
7. Differentiate between Motor and
sensory nerve fiber
8. Advantages
9. Disadvantages
10. Donor site morbidity
11. Co-contraction in nerve transfer
12. Types

1. Nerve Transfer on Peripheral Nerve Injury -By Atanu Ghosh (BPT, Final Year)

2. INTRODUCTION A nerve transfer is a procedure during which a surgeon takes a healthy, redundant, functioning nerve fiber (donor nerve) and reroutes it to connect to a nonfunctioning, damaged nerve (recipient nerve). This allows nerve fibers (axons) from the donor nerve to grow through the recipient nerve.

3. Nerve degeneration and regeneration occurs after nerve injury, and is influenced by immune cells and cytokines. Nerve degeneration begins within 24 hours of injury and is complete within 3 weeks. The distal portion of the axon, which is disconnected from the cell body, undergoes Wallerian degeneration, which is a process that causes the axon to break down and disintegrate. Glial cells, mainly macrophages, remove the debris. Nerve regeneration is possible if the nerve cell body and nucleus remain intact, and the cut ends are within 3mm and aligned. Regeneration occurs 1mm/day averagely in peripheral nerve injury. Nerve Degeneration to regeneration

4. In the cases of unsuccessful regeneration within 12 months, normal muscle atrophy get started which can be reversible after the muscle get innervated and the muscle get into daily use. But after 12 months the muscle get started an irreversible atrophy which can’t be reversed at all. This time period may vary from 12 to 18 months on depending on many factors. In the cases of unsuccessful regeneration

5. Irrecoverable proximal nerve injury (i.e. Root avulsion). If a long nerve graft is required. Long distance between injury site and motor endplates. Late presentation. Very wide injury and dense scar tissue. Indications for nerve transfer

6. Existence of a better option. Time since injury over 18 months. Motor donor strength below Medical Research Council (MRC) grade M4. contraIndications for nerve transfer

7. Purely motor or sensory, Containing enough axons to re-innervate the recipient muscles, its diameter is similar to the recipient nerve, Requires no nerve graft, Innervates expendable muscles and has synergistic function with the recipient nerve. The functional loss created on taking the donor should be less important than the functional recovery expected on re-innervating the recipient. Post-operative rehabilitation is easier when donor and recipient nerves have a synergistic action. In the case of antagonistic action, much more post-operative re-education will be needed to recover the same amount of function. The recovery of muscle power depends on the amount of motor axons provided by the donor nerve and on the time elapsed until re-innervation happens. It is known that a muscle generates a normal power until about 80% of the motor axons are lost, but afterwards, there is a sharp loss. Thus, it is crucial to be above this 20%. Ideal donor nerve

8. Differentiating motor and sensory fibers in a mixed nerve is crucial for successful nerve transfer. Here are some methods used to differentiate and identify motor and sensory fibers: Anatomical identification: Knowledge of nerve anatomy and branching patterns helps identify motor and sensory branches. Fascicular pattern: Motor fibers tend to be grouped together in larger fascicles, while sensory fibers are in smaller fascicles. Fiber size and color: Motor fibers are typically larger and lighter in color, while sensory fibers are smaller and darker. Electrical stimulation: Stimulation of the nerve and observing muscle contraction or sensory response helps identify motor and sensory fibers. Nerve conduction studies (NCS): Measuring nerve conduction velocities and amplitudes helps differentiate motor and sensory fibers. Histological examination: Examining nerve biopsies under a microscope can help identify motor and sensory fibers based on their histological characteristics. Immunohistochemical staining: Using specific markers, such as neurofilament or synaptophysin, can help identify motor and sensory fibers. Intraoperative nerve monitoring: Using techniques like electromyography (EMG) or nerve stimulation during surgery helps identify motor and sensory fibers in real-time. By combining these methods, surgeons can accurately identify and separate motor and sensory fibers in mixed nerves, ensuring successful nerve transfer and optimal functional recovery. Differentiate between motor &sensory nerve fibers in mixed nerve

9. Shorter distance between donor healthy nerve and denervated muscle endplates. Safe supply of viable axons. Usually no nerve graft is needed. Selection of pure motor or sensory axons. Possibility to recover more than one function. Less scar in the surgical field. Faster recovery. Long term durability. advantages for nerve transfer

10. A function has to be sacrificed. Donor site morbidity. Donor and recipient muscle co-contraction. Possibility of previous donor nerve injury. disadvantages for nerve transfer

11. Donor site morbidity in nerve transfer surgery refers to complications that arise at the donor site after surgery, including: Sensory loss, pain, Functional impairment etc. Example : Shown in the Spinal Accessory nerve (SAN) to Suprascapular nerve (SSN) transfer. The weakness of the middle and lower part of the Trapezius muscle (donor site) induces mild scapular winging in the case of good recovery of shoulder external rotation which is performed by Infraspinatus and Teres Minor muscles. Donor site morbidity

12. Co-contraction in nerve transfer refers to the simultaneous activation of both the agonist and antagonist muscles, leading to: Reduced muscle force, Increased muscle fatigue, Abnormal movement patterns ,Impaired proprioception, Functional limitations etc. Example : It can be useful in the case of synergistic action between donor and recipient muscles. This is the case in the SAN to SSN transfer as the trapezius is synergistic with the supraspinatus and infraspinatus action. In most other cases of antagonistic, it is an inconvenience. For example, in the Oberlin procedure [a fascicle of the ulnar nerve (UN) is transferred to the biceps muscle (BM) nerve branch], there is a tendency for finger flexion when attempting elbow flexion. Co-contraction in the case of nerve transfer

13. Types of nerve transfer

14. A) End-to-end anastomosis : The distal stump of the donor nerve is coapted with the proximal stump of the recipient one. It is the best option for all nerve transfers, and the only successful one in motor restoration. B) End-to-side anastomosis : The proximal end of an injured nerve is coapted to the side of a healthy one after creating an epineurial window in it . The idea is that the axons of the healthy nerve create lateral sprouts that grow inside the damaged one. C) Reverse end-to-side or ‘supercharge’ end-to-side anastomosis : A healthy nerve is transected and coapted to the side of a damaged one. The idea is that the axons of the healthy nerve grow inside the injured one. It provides a fast muscle re-innervation with preservation of the muscle bulk until the axons of the damaged nerve regenerate and reach their own endplates. This avoids muscle atrophy while the injured nerve axons regenerate. Anastomosis of nerve transfers

15. Anastomosis of nerve transfers

16. Any Questions