Nerve injury

Overview

Your motor and sensory nerves regulate your movement and allow you to experience temperature, pressure, and pain. They are weak in comparison to your bones; they may be harmed by excessive pressure, being stretched too far, or being cut. In all of these cases, you will experience pain, numbness, or weakness, or a combination of these symptoms.

These nerves are part of your peripheral nervous system, which includes everything except your brain and spinal cord. Peripheral nerve injuries are rather common. Sports injuries, trauma such as a car accident or a fall, or overuse can all result in them.

 

What is a nerve?

Nerves are part of the "electrical wiring" system that connects the brain to the rest of the body. Motor nerves transmit information from the brain to the muscles, causing the body to move. Sensory nerves transmit information from the brain to other regions of the body to indicate pain, pressure, and temperature.

Nerve contains bundles of separate nerve fibers and a sheath around it. A ring of tissue surrounds the nerve, protecting it in the same way as insulation surrounds an electrical line. Nerves are made up of several fibers known as axons. Within the nerve, these axons are organized into bundles. The bundles are surrounded by tissue layers, exactly as the nerve's outer tissue layer.

 

What happens when a nerve is injured?

Clinical examination is frequently paired with electrodiagnostic procedures to determine the location and degree of a peripheral nerve damage. Myelin injuries are generally the least severe (neuropraxia), whereas axon and supporting structure damage are more severe (axonotmesis is moderate injury, while neurotmesis is severe injury). Because of common neurological deficits, such as motor and sensory impairments distal to the lesion, it may be difficult to identify severity based on clinical symptoms.

There are three basic types of injury to a nerve:

    1. Neurapraxia

Neurapraxia is the mildest kind of nerve damage, with full recovery. The axon remains intact in this situation, but myelin loss prevents the impulse from traveling down the nerve fiber. The most common cause is nerve compression or an interruption in the blood flow (ischemia). Within hours to months following the damage, there is a transient loss of function that is recoverable (the average is 6–8 weeks).

Because Wallerian degeneration does not occur, recovery does not need regeneration. Motor function is often more involved than sensory function, with autonomic function intact. At day 10, electrodiagnostic testing with nerve conduction studies reveals a normal compound motor action potential amplitude distal to the injury, indicating minor neurapraxia rather than axonotmesis or neurotmesis.

     2. Axonotmesis

This is a more severe nerve damage with neuronal axon disruption but epineurium preservation. This form of nerve damage, which is most common in crush injuries, can result in paralysis of the motor, sensory, and autonomic nervous systems.

If the force that caused the nerve injury is removed quickly, the axon may regrow, leading to recovery. Electrically, the nerve degenerates rapidly and completely, with loss of voluntary motor units. As long as the endoneural tubules remain intact, regeneration of the motor end plates will proceed.

Axonotmesis is the interruption of the axon and its myelin sheath while the nerve's connective tissue scaffolding is intact (the encapsulating tissue, the epineurium and perineurium, are preserved). Wallerian degeneration occurs when axonal continuity is lost. EMG done 2 to 4 weeks later reveals fibrillations and denervation potentials in the musculature distal to the lesion site. Axonotmesis causes more extensive loss in both motor and sensory spines than neurapraxia, and recovery occurs exclusively by axon regeneration, which takes time.

Axonotmesis is more commonly caused by a severe crush or bruise than neurapraxia, but it can also occur when the nerve is stretched (without damage to the epineurium). There is always some retrograde proximal axonal degeneration, and for regeneration to occur, this loss must first be overcome. Regeneration fibers must pass via the damage site, and regeneration through the proximal or retrograde region of degeneration may take many weeks.

 The neuritis point then spreads to the distal location, such as the wrist or hand. A proximal lesion can expand distally at a rate of 2 to 3 mm per day, whereas a distant lesion can grow at a rate of 1.5 mm per day. Regeneration takes weeks to years.

     3. Neurotmesis

Neurotmesis is the most serious lesion, with no chance of complete recovery. It develops as a result of a severe contusion, strain, or laceration. The axon and enclosing connective tissue are separated. The last (extreme) degree of neurotmesis is transsection, however most neurotmetic injuries do not result in a complete loss of nerve continuity but rather in internal disruption of nerve structures sufficient to affect perineurium and endoneurium as well as axons and their covering.

EMG denervation alterations are identical to those found with axonotmetic damage. Motor, sensory, and autonomic function are completely lost. If the nerve has been totally severed, axonal regrowth results in the formation of a neuroma in the proximal stump. It is preferable to adopt a newer, more comprehensive categorization known as the Sunderland System for neurotmesis.

To continue with the analogy of the telephone wire. When the inner cables (nerve fibers) are injured, the portion of the cable above the level of the lesion dies, leaving an empty tube. The inner cable above the level of the damage is still alive because it is fed by nerve cells near or within the spinal cord. Inner cables (nerve fibers) must grow back down the tubes for the nerve to heal. This sort of injury's recovery is more variable.

The Surgeon can only mend the surface layer and not the small inside wires (nerve fibres). We know that not all inner cables (nerve fibers) will self-repair, and that those that do will be attached to the incorrect residence. This implies that numerous incorrect numbers will be acquired following a repair. The brain, like the telephone exchange operator, will do its hardest to make sense of the new numbers but will fall short. This indicates that there will always be a residual and permanent loss of function following a nerve restoration.

Recovery from any nerve damage is unpredictable. Unfortunately, as we age, our nerves recuperate less well. This is due in part to the ability of the younger nervous system to adjust to the lack of normal nerve function.

 

Signs and Symptoms

The indications and symptoms of a nerve damage vary based on the affected nerve, the kind of injury, and the degree of the injury. Some examples are:

• Numbness: Because certain nerves only convey feeling, a nerve lesion to these nerves would result in some numbness.
• Weakness: Some nerves, in addition to sensory nerves, offer you the capacity to move, while others do both. Injury to nerves that convey motor impulses results in some weakness.
• Pain: This is a common sign of nerve damage. Pain from a nerve damage can occur anywhere along the nerve's path, although it is most commonly felt near the location of the lesion.

Nerve damage symptoms might be intermittent if the injury occurs often, or they can be persistent if the injury is serious enough. Other symptoms of nerve damage include muscle shrinkage, skin color changes, and variations in the quantity of perspiration produced in certain locations.

Carpal tunnel syndrome is one example of a recurring nerve damage. Carpal tunnel syndrome develops when the median nerve is compressed as it passes the wrist. Numbness in the hand, discomfort in the hand, pain in the wrist, pain in the forearm, or weakness (especially in the thumb) may occur. Carpal tunnel syndrome symptoms can be sporadic or persistent, depending on severity.

 

Nerve Injuries of the Hand, Wrist and Elbow

The upper extremity of the body has several nerves that travel between the shoulder and the fingertips. These nerves are in charge of transmitting instructions from the brain to regions of the arm that control movement, sensation, and reflexes. The nerves of the upper extremities exit the central nervous system at multiple locations in the neck, forming a complex structure known as the brachial plexus (link is external). Near the neck, the nerves grow greater in diameter and eventually split to generate smaller branches in the upper arm, forearm, and hand.

Upper extremity injuries can occasionally produce nerve damage, interfering with the numerous functions of the arm and hand. The nerve is occasionally injured, and it may heal on its own over time. However, if a nerve is severed or crushed, surgical therapy may be required to enhance or restore function to the hand or arm. Certain disorders can sometimes impact nerves and create symptoms in the upper extremities.

 

Common peripheral nerve injuries 

The following are some of the more common peripheral nerve injuries. 

 

Brachial plexus or “burner” neck/shoulder nerve injury

A brachial plexus injury is a type of peripheral nerve injury that affects the nerves that run from the neck to the arms and hands. The brachial plexus is a group of nerve roots that connect to your spinal cord on both sides of your neck. They divide and go down each arm. Sharp pain flowing from your neck into your shoulder and arm, often with numbness and/or paralysis, is the predominant sign of nerve injury here. This sort of injury can occur as a consequence of a car accident, a fall, or participation in sports.

Because of the neck or shoulder pain, the injury is known as a "burner" or "stinger" in sports. In a poll, two-thirds of college football players reported burners, but the majority of them never disclosed the injury while on the team.

 

Radial nerve injury 

The radial nerve runs down the inside of your arm, into your wrist and fingers. It is in charge of your triceps muscle as well as your capacity to stretch your wrist and fingers. If you break your arm, you will have radial nerve damage. Workplace injuries or overuse can potentially harm this nerve. Symptoms include discomfort and numbness, as well as lack of mobility in your wrist, hand, or fingers.

 

Carpal tunnel syndrome

Carpal tunnel syndrome is a common cause of peripheral nerve entrapment. The median nerve, which provides sensation to your thumb and the following three fingers, has become inflamed and swollen. It must pass through a tight area, the carpal tunnel, as it goes into your hand. If the nerve is enlarged, it cannot readily pass through the tunnel, causing numbness and discomfort in your thumb, fingers, and the side of your hand where your thumb is. Working with your hands all day, whether on a computer or with a hammer or drill, raises your risk of carpal tunnel disease. 

 

Ulnar elbow entrapment or bicycler’s neuropathy 

Your ulnar nerve aids in the movement of your hand and lower arm. This nerve originates in the brachial plexus and travels down your arm, via your elbow, and into your wrist. It can become ensnared at a location called the cubital tunnel on the outside of your elbow. Because the tunnel is so small, if the nerve is compressed, you will feel pain, weakness, and tingling in your lower arm and hand. 

 

Ulnar wrist entrapment 

The ulnar nerve can also be squeezed when it travels through a tiny canal at the wrist. It's related to carpal tunnel syndrome, except it affects other nerves. If you ride a bike or play golf, tennis, or baseball, you are more likely to sustain this injury. You are frequently straining the nerve by grasping your equipment with your hands.

 

Symptoms of Nerve Injuries of the Hand, Wrist and Elbow

Symptoms usually appear after an injury to the neck, shoulder, arm, or hand. Symptoms might appear as a result of anything as simple as resting on the arm for an extended period of time. Other injuries might develop as a result of a crush or a severe cut along any region of the nerve. Common nerve damage symptoms include:

• Sensation loss in the upper arm, forearm, and/or hand. Each nerve provides sensation to a separate part of the upper extremity. The pattern of numbness might assist the surgeon in locating the damaged nerve (s).
• Upper arm, forearm, and/or hand function loss Different nerves supply the muscles of the upper extremities. Muscles that do not function adequately assist the surgeon in locating the affected nerve (s).
• Wrist drop or inability to extend the wrist
• Decreased muscle tone in the upper arm, forearm, and/or hand
• Changes in sweating patterns of the upper arm, forearm, and/or hand

 

Diagnosing Nerve Injuries of the Hand, Wrist and Elbow

Patients may see more than one physician, surgeon, therapist, or physician assistant depending on the severity of their ailment. Consultations often run between 1-2 hours. Patients should expect the following during this critical visit:

• Undergo a physical examination and provide a detailed medical history, including previous surgical operations, past and present medical problems, and any current drugs or herbal supplements.
• Discuss treatment options for the illness, including if surgery is required. If surgery is required, patients will be given a thorough explanation of the procedure's risks and dangers, as well as the recovery and rehabilitation duration and the likely outcome in terms of function and appearance.

In addition to an initial consultation appointment, additional diagnostic tests may be ordered. These include:

• Electrodiagnostic nerve studies (EMG)
• X-ray: Images used to determine if fractures are present
• CT Scan, MRI, or ultrasound (US) for more detailed imaging

 

Treatment for Nerve Injuries of the Hand, Wrist and Elbow

Surgical therapy is determined on an individual basis and is determined by the location, duration, and kind of nerve damage. The purpose of surgery is to improve upper extremity function in the afflicted region. If the nerve is believed to be repairable, surgical therapy may include:

• Nerve decompression
• Nerve repair
• Nerve graft

A tendon transfer may be considered if nerve restoration is not a possibility. Tendon transfers use additional tendons from other areas of the hand or forearm to replace a function lost owing to nerve damage. The tendon was chosen such that the patient does not lose function when the donor tendon is used.

 

Hand Therapy and Rehabilitation

The ultimate objective of therapy and rehabilitation is to restore and optimize hand function, as well as to regain independence and enhance overall quality of life. We provide treatment regimens that are customized to each patient's health, lifestyle, and employment requirements:

• Non-surgical option: For patients who do not require surgery but would benefit from therapy.
• Post-operative rehabilitation: To help patients as they recover from surgical procedures.

 

What are the complications of a nerve injury?

When a nerve is wounded and the inner cables (nerve fibres) are broken, the fibres that can't find their way down the empty tubes shoot out and create a neuroma, which is a bundle of disconnected nerve terminals. Because these endings are still linked, a neuroma can provide a variety of unpleasant feelings if hit or touched.

When a nerve is significantly injured across a long distance, it may be impossible to restore the ends immediately. After a repair, the nerve may not show any indications of recovery. In either of these cases, the nerve may need to be repaired by inserting nerve grafts, which are segments of other nerves. This will result in a minor loss of feeling in the area where the nerve graft is extracted.

Other potential complications following a nerve repair might be discussed with your Surgeon or Therapist.

 

Recovery

• Joint flexibility can be maintained by physical therapy. Even once the muscles begin to operate again, if the joints become stiff, they will not function.
• Because there is no feeling in the afflicted area if a sensory nerve is damaged, care must be taken not to burn or cut fingers.
• The brain may need to be "re-educated" after a nerve damage. Sensory re-education may be required once the nerve has healed to improve feeling in the hand or finger. Based on the kind and location of the injury, the doctor will suggest suitable physical treatment.

Age, the kind of wound and nerve, and the location of the damage are all factors that may influence the outcome of nerve restoration. Although nerve injuries can cause long-term issues, appropriate treatment can help patients return to more normal function.

 

Conclusion 

Nerves can be harmed in a variety of ways, including a crush injury or laceration of the finger or wrist. In most situations, nerve damage will have surgical repair in order to restore feeling and muscle strength and movement. If your nerve was surgically repaired, your rehabilitation plan may include wearing a splint to safeguard the repaired nerve. When necessary, you may be offered a home exercise regimen, as well as wound and scar care guidance and sensory re-education for the mending nerve.