Introduction
A nerve may get injured due to several reasons. The surgeon removes the damaged portion and places a nerve graft to bridge the gap between two ends of a nerve. The nerve graft can be transplanted from the same person or a different person. This procedure is a good treatment option that benefits patients with nerve injuries to get their senses back.
What Is a Nerve Graft?
A surgeon repairs a damaged nerve by connecting it with a new nerve transplanted from another site in the body. This helps in reinnervating the injured nerve and bringing its function back. The complete recovery and functioning of the nerve depend on the body’s ability to satisfy all the variables for nerve regeneration.
What Is the Anatomy of a Nerve?
Nerves are the structures that help transmit signals. Each nerve cell is called a neuron. The neuron consists of a cell body, axon, and dendrites. The cell body and dendrites receive information from other neurons, whereas the axon helps transmit information to other neurons. Motor nerves are those that help in muscle function and body movements. Sensory nerves signal the different senses felt in the body, like pain, touch, pressure, and temperature.
How Does the Nerve Get Damaged?
The nerve gets damaged by any of the following reasons:
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The nerve may get injured due to trauma which can stretch or compress the nerve.
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Patients with diabetes mellitus (where the nerve damage is one of the main complications), Guillain-barre syndrome (a disease affecting the nervous system), and carpal tunnel syndrome (a condition compressing the median nerve in the forearm).
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Patients with autoimmune diseases like rheumatoid arthritis, lupus, and Sjogren's syndrome may also suffer from nerve damage.
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Tumor growth near the nerve can also lead to its damage.
The nerve injury can be of three types according to Seddon’s classification:
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Neuropraxia - It is a compression type of injury to the nerve and is one of the mildest forms. It causes focal degeneration of the myelin sheath (a protective layer around the nerves) without damaging the axon and the surrounding tissues.
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Axonotmesis - A more severe form of injury than neuropraxia. The myelin sheath and the axon are damaged here, but the surrounding tissues are intact. It is a crush type of injury.
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Neurotmesis - The nerve is completely cut. The myelin sheath, axon, and connective tissues around the nerve get damaged. This is the most severe form of injury and results in paralysis of the part supplied by the nerve.
The patient can suffer from nerve damage of any of the types mentioned above, and it is up to the doctor to decide the appropriate treatment for its repair.
What Are the Types of Nerve Grafts?
Depending on the person from whom the nerve graft is taken, there are two types:
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Autograft - It is taken from a different site in the same person. The sensory nerve from the part where the sensation is not essential is removed and transplanted to repair the damaged nerve.
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Allograft - It is a graft taken from a different person or a cadaver (dead person). This nerve is sterilized, processed, and then transplanted to the donor patient to avoid graft rejection reactions.
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Conduits - These include the use of artificial nerve tubes instead of a nerve. Artificial nerve tubes are made of synthetic bioabsorbable material and aid in nerve regeneration when the standard nerve grafting between the severed nerve is impossible.
The nerve grafts are given the first preference, after which the conduits are considered. The nerves commonly involved in grafting are the sural nerve (nerve providing sensation to the legs), posterior and lateral cutaneous nerve of the thigh, medial and lateral antebrachial cutaneous nerve supplying the forearm, and dorsal cutaneous branch of the ulnar nerve. Of these, the sural nerve is the most commonly transplanted.
Who Are the Right Candidates for a Nerve Graft?
Nerve grafting is not indicated for all patients with nerve injury. Some factors determine if nerve grafting is suitable for the patient. They are:
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A prolonged time after the nerve injury does not allow the nerve graft to regenerate. The nerve graft must be placed within six to twelve months after injury.
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If the size of the damaged nerve is about 5-14 millimeters, nerve grafting is done. If it is longer than that, a nerve transfer can be done.
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If the nerve is cut with a sharp object, the surgeon tries to repair it rather than placing a graft.
How to Find Out if the Nerve Is Damaged?
The person suffering from nerve damage may initially experience certain symptoms. The symptoms include:
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Muscle weakness.
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Uncontrolled twitching of the muscles.
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Numbness or tingling sensation.
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Difficulty in sensing touch, pain, temperature, or pressure.
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Excessive sweating.
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Loss of balance.
The patient must consult with the doctor immediately if they notice any of these changes. The doctor runs a few tests to confirm the nerve damage. They are:
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Electromyography - A test used to measure the function of muscles and nerves with the help of a thin needle electrode. A reduced muscle function indicates nerve damage.
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Nerve Conduction Study - A test to measure the speed with which the nerve impulse travels within the neuron. Two electrodes are placed on the nerve to be tested. One electrode stimulates the nerve and the second electrode records it. The speed of the impulse is measured by recording the distance and the time interval of the impulse between the two electrodes.
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Magnetic Resonance Imaging (MRI) - A soft tissue imaging technique that uses magnetic and radio waves. This technique detects any structural abnormalities that may be compressing the nerve. The lesion pressing the nerve is identified and removed to prevent permanent nerve damage.
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Ultrasound - Similar to MRI, it produces images of the nerve that helps in finding any presence of damage.
The doctor takes a detailed patient history and performs physical and imaging tests to finally come up with a perfect diagnosis and treatment plan.
How to Perform Nerve Graft Surgery?
Nerve grafting as a treatment option for the patient is decided after considering factors like the size of the nerve gap, site of nerve repair, and donor site morbidity (pain, scarring, discoloration, and infection). The doctor explains about the procedure in detail, and the patient signs a consent form as a sign of approval.
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The surgery is performed under general anesthesia.
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The site from which the nerve graft is taken is first incised.
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Small incisions are given along the nerve to pull off the nerve of the required length.
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The cut ends of this nerve are placed into nearby muscles to avoid any scar formation.
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The damaged nerve is incised, and the injured portion is removed.
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After removing the damaged portion, the gap is replaced with the nerve graft taken from the donor site.
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The nerves are connected using sutures, and the incision is closed with sutures.
How Is the Recovery After a Nerve Graft Surgery?
The patient can discharge from the hospital after a few hours or the next day. Complete recovery takes several months.
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The surgeon places a sling on the operated site to immobilize it and provide good healing. The splint is placed for about two to three weeks, after which the surgeon removes it.
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A nerve grows about an inch per month. So it takes a couple of months for the nerve to regenerate fully.
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Physiotherapy is advised to the patient after a few months to regain the function of the affected limb.
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Do not perform heavy exercises that cause strain to the body.
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Smoking habit is avoided as it may interfere with the healing process.
The patient may experience numbness over the donor site for a few days, but it gets relieved over time. Sometimes, the function of the damaged nerve may not be regained. After all, it depends on the patient’s age, underlying medical condition, size and location of the damaged nerve, and the surgeon’s skill for the complete success of the procedure.
How Is Nerve Graft Different From Nerve Transfer?
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In nerve grafts, a portion of the nerve is removed from a donor site (autograft or allograft) and placed between the two ends of the damaged nerve. The nerve regenerates between the donor and the recipient's nerve and regains its function.
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In nerve transfer, one of the healthy nerves is cut and joined with the end of the damaged nerve. This allows the healthy nerve to grow into the damaged nerve and restore its functions. In cases where a functioning nerve is adjacent to the damaged nerve, a nerve transfer is a better treatment option than a nerve graft.
Conclusion
Nerve grafting is a procedure to bridge the gap between the damaged nerve and restore its functionality. It is one of many treatment options available for injured nerves. Nerve grafts are usually successful with shorter gaps and have a better recovery rate. Large gaps can be treated with nerve transfer. Hence, the doctor decides on the right treatment option for the patient after considering the various factors for the best cure.
