Nerve Damage: Overview, Classification & Types, Nerve Repair Process, Non Surgical & Surgical Treatment, Nerve Allograft, Recovery

“Injuries on and often is a part of normal life. It is the life which needs to adjust to the pain and suffering which follows injury!” Every human being has met with problems of being injured. Some injuries are external and some are internal. Nerve damage or nerve injury is one of the most painful soft tissue damage observed following trauma or accident. Nerve injury may result in a peripheral and central suffering associated with tingling, numbness or losing the feeling or sensation and often results in abnormal muscles functioning.

Nerve damage is treated with conservative therapy or surgery. Injured nerve is often treated surgically and repaired for regaining the proper functioning of the body. There are many surgical as well as non-surgical techniques for treating damaged nerve, which has been practiced since long in medical science. In the current article, we will be discussing nerve damage & nerve repair. We will discuss in detail nerve damage or nerve injuries, the nerve repair treatment & nerve repair techniques known till date. The topic will also cover a recent novel surgical treatment of repairing damaged nerve known as “Nerve Allograft”. The article provides information of advanced and beneficial surgical and non-surgical treatment to treat and repair damaged nerve.

Nerves are very much fragile and can get easily damaged with excessive pressure, stretching or cutting. Nerve injuries may result in abnormalities of sensory, motor or mixed function of the nerve. Nerve injury interrupts and restricts passage of signals from and to the brain. The signal going to the brain may be associated with tingling and feeling of loss of sensation. While interruption of the signal coming from brain and going to muscles may result in improper muscle functioning in the damaged area. Nerve injury may be caused by sharp or blunt trauma. Blunt trauma follows fall and accident, while sharp trauma follows penetrating injury or direct cut from any sharp object like knife. So coming to a generalized section of various causes leading to nerve damage or nerve injuries, here below we can list some of the most important causes.

• Penetrating or slicing wounds
• Injury due to accidents that causes a pressure or stretch in the nerve
• Stretching due to excessive movement
• Laceration
• Drug or medication injection over the nerve resulting in nerve injury
• Compression of peripheral nerve
• Electrical injury.

Whatever may be the cause of nerve damage or nerve injury, it surely requires a repair. Sometime the mild injuries get automatically repaired with natural process of healing inside the body. However, there are conditions where the nerve injuries get so much severe that the victim requires immediate treatment which may also include surgical reconstructions. The following array will discuss more about the nerve damage and nerve repair techniques.

Before understanding the types of nerve damage or nerve injuries and their repair processes, let us have a brief knowledge on the nerve anatomy.

Nervous system is an “Electric wiring system” in the body, which comprises the nerves for carrying signals from and to the brain. There are motor and the sensory nerves densely spread in all the tissues of the body, the network comprises of highly sophisticated natural system of electrical wiring. The motor nerve carry signals between the brain and the muscles for making the body movements, while the sensory nerves carry signals from various parts of the body to brain and spinal cord so as to inform the brain about the pain, pressure and temperature. The general anatomy of nerves is explained below.

• A nerve comprises of a several nerve fibers enclosed in a fibrous capsule.
• The nerve fibers are termed as axone.
• The axons are further protected by the tissue layers known as myelin sheath. The outer tissue ring protects the nerves.

There are various types of nerve injuries seen in a body. Let us list some of the most important types of injuries to nerves.

1. Neuropraxia: In this type of nerve injury, there is only a physiological block of the nerve conduction within an axon and there is no anatomical interruption. This type of nerve injury gets disappeared in 6 weeks. Many new born babies born with birth brachial plexus injury do have neuropraxia.
2. Axonotmesis: In such a type of nerve injury, there is an anatomical interruption of the axon. There may or may not be an interruption of the connective tissue network in this case. Such a kind of injury to the nerve may take a longer period to get repaired or to regrow which may range from 4 weeks to around 18 months (As per the level of damage and conditions). Here the regrowth of the nerve fiber (axon) can be inhibited by scar formation. A patient might also require surgical treatment, which depends on the number of damaged axons and the extent of scar formation.
3. Neurotmesis: Neurotmesis is actually a condition of nerve rupture. In this type of nerve injury, there is a total anatomical disruption of the axon as well as the surrounding connective tissue.

1. First Degree Injury- There is a reversible local conduction block at the injured site which do not need surgical treatments
2. Second Degree Injury- Here there is a loss of continuity of nerve fiber within the nerve. This type of injury also does not require surgical treatments in general.
3. Third degree injury- In such type of injuries, there is damage to the nerve fiber (axon) as well as the surrounding parts in the nerve. This might require extensive nerve repair technique of grafting or may also be repaired with simple cleaning of damaged nerve (as per the conditions).
4. Fourth Degree Injury- In this type of injury there is usually a prevention of nerve regeneration due to scarring involved with it. Such a type of nerve injury happens when there is damage to the axon as well as the surrounding tissues in the nerve which results in scarring. In fourth degree injury there is a requirement of surgical intervention with nerve grafting.
5. Fifth Degree Injury- Fifth degree injury is the most severe type of nerve damage where the nerve gets divided into two. This occurs due to excessive stretching of nerves or laceration. There is a mandatory requirement of surgery to treat such nerve injuries.

Nerve repair is not a rapid process in case of mammals. It takes time, healing is painful and requires lot of patience during healing period. Even minor nerve injuries do take around a months’ time to heal. Let us understand this nerve repair process in humans which is actually a slow process.

• Neuropraxis- In case of the neuropraxia, the myelin sheath is injured and not axon or nerve fibers. The injury is caused by blunt trauma. The injury leaves an empty axonal tube, which covers the nerve fiber. Following initial period of shock of 2 to 5 days the myelin sheath repair begins and takes over 4 to 6 months for complete healing. The repair and healing takes place at a slow rate of about one inch per 4 weeks. The nerve fiber grows inside the empty axonal tube. The minor injury often takes about a month to get repaired. Nerve repair is not needed.
• Neurotmesis- In case of neurotmesis (and maybe also sometimes axontomesis), the myelin sheath and axon are badly damaged. The injury may result in formation of a twisted ball of nerve fiber known as neuroma (nerve scars or bundle of nerve ending). The neuroma is formed when a nerve growth is obstructed by a scar tissue anywhere along it’s pathway. Neuroma is extremely painful swelling of nerve. Nerve ends in coil following obstruction by scar tissue, which lies in the pathway of its normal course. Nerve repair is often difficult when neuroma is formed. In case of severe intractable pain, surgeon may try to excise the neuroma for pain relief.
• Incomplete Healing- It must be noted that there are also chances that the regrown nerve does not meet up finely with the original muscles and sensory organs, which may in turn lead to a significant loss of certain function on a permanent basis. Incompletely healed nerve often responds to surgery.
• Nerve Repair Surgery- The current medical practice involves a nerve repair process where there is a use of some micro structures (grafts) for reconstructing the cut ends of the axon in a unique surgical process. This process of nerve repair actually intends in providing a continuous axon for guiding the regrowth of the nerve fiber. It must be noted that there are also some effective non surgical nerve repair process, which can be practiced for the nerve regrowth. But again the same point arrives; “nerve repair is always a slow process in mammals”

Below are some of the possible non-surgical therapies which can prove essential in case of nerve repair.

• Acupuncture/Electric Acupuncture: Acupuncture is a traditional Chinese process of healing which can be used to regenerate the damaged nerves and help in nerve repair in an effective way. Studies have found that electric acupuncture has some real effective results in treating nerve injuries.
• Low Power Laser Irradiation or Laser Phototherapy: Laser phototherapy can be a possible physical therapy used to repair the damaged nerve. Here a low power laser is exposed to the damaged end of axon which helps in altering nerve cell activity, by inducing the growth of neurotrophic growth factors.
• Low Frequency Electric Stimulation: Animal studies have found that low frequency electric stimulation has proved beneficial in nerve regeneration.

The most accepted treatment for severe nerve injury is the surgery. The following section will elaborate the surgical nerve repair technique and highlight the recent advances published in medical science journal regarding the ‘nerve allograft” or nerve repair technique.

• Accurate Diagnosis- The first step that begins before surgical treatment is to pinpoint the area of nerve injury. The patient is evaluated by neurologist and neurosurgeon. Detailed history and examination is conducted to evaluate the sensory and motor nerve function and area of nerve damage. Nerve conduction studies and EMG test is performed to evaluate severity and nerve function. Radiological studies like soft tissue MRI and ultrasound studies are performed to evaluate the area of trauma causing nerve injury.
• Nerve Graft Insertion- The area of injury is located and extent of injury is analyzed. The injured nerve is replaced with another nerve known as auto-graft. The nerve from another part of the body is removed and used as a graft. The mechanism of surgical nerve repair technique involves the use of a nerve graft from a donor part of the body so as to fix in the injured nerve. The graft used in surgical treatments for nerve injuries is usually autograft, i.e. graft taken from the patient’s own body from some other part called the donor site.
• There are also uses of nerve conduit in treating nerve injuries. However there is a novel discovery in recent times where a nerve allograft is used to repair the damaged nerve. The immediate next section of this article will include the recent discovery of “nerve allograft” as a new nerve repair technique.

• Researchers from university of Kentucky have come up with a wonderful novel technique of nerve repair which promises the appropriate healing of an injured nerve in a much efficient manner with comparatively less side effects as compared to the traditional nerve repair techniques of autograft and conduit nerve repairs. This newer nerve repair technique uses a ‘nerve allograft’ for the nerve repair.
• Usually the severe injuries and the injuries which are not clean cut; usually results in the formation of gaps in the nerves. These gaps are required to be sewn or filled up while the nerve repair surgical treatment process is undergone in the patient.
• Surgeons usually go for autografts or the nerve conduits to fill these gaps. In case of the autografts, the patient’s own nerve from some other part of the body is used as the graft. The part from where the graft is taken is termed as donor site. The drawback with this is the donor site loses the feeling as a result of a nerve deficit at the place. In case of nerve conduits there are chances of infections or foreign body reactions.
• The recent nerve repair technique developed by the researchers from University of Kentucky, guided by Dr. Brian Ricker; uses the “nerve allograft”, which make use of human nerves grown from cadavers. This proves to be a much safer technique for nerve gap repair with less chance of side effects and more consistent results for better results than the nerve conduits. This also eradicates the issue of nerve deficit caused in donor site; seen in case of autograft.
• The nerves harvested from cadavers are processed for removing all the cellular materials present while keeping the architecture intact and eradicating the side effects of disease transmission or allergic reactions.
• The researches followed a study which was funded by Axogen, Inc. And their results were presented at the American Association for hand surgery, Americal Society of Reconstructive Microsurgery and the American Society of the Peripheral Nerve. The study was based on the patients with nerve conduits and nerve allografts in the nerve repair techniques and found better results seen in the patients with nerve allografts with comparatively less side effects.

• The patient’s age is one of the most crucial factors in case of the sensory recovery after the nerve repair. It is usually found that the repair of damaged nerve starts declining after the age of 20. It is found there are chances of 75% positive results in children as compared to 50% positive results in adults. The results of recovery after age of 60 is pretty much poor.
• Among other factors that explain the efficacy of nerve repair include the type and location of injury and the type of nerve injured.
• The process of healing is very slow. It is found that the nerve advances 1mm each day.
• It might happen in some kinds of nerve injury, the brain may need to be “re-educated” with some sensory training done by certain physical therapies practiced by the physician so as to improve the sensory feelings in parts of damage.

Also Read:

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• Peroneal Nerve Injury Due To Knee Joint Trauma-Causes, Symptoms, Treatment
• What is Radial Nerve Injury: Causes, Symptoms, Treatment, Prognosis, Diagnosis
• Median Nerve Injury: Symptoms- Numbness, Weak Grip, Treatment- R.I.C.E, Surgery
• Ulnar Nerve Injury: Causes, Symptoms, and Treatment