Complications with Peripheral Nerve Injury

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Introduction

Peripheral nerve injuries are common conditions with broad ranging symptoms depending on the severity of the nerve injury and what nerves are involved. Peripheral nerves convey signals between the spinal cord and the rest of the body. Nerves are comprised of various combinations of motor, sensory, and autonomic neurons with symptoms and complications dependant on which nerve fibres are involved .

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Motor Nerves; Damage to these nerves are typically associated with muscle weakness, muscle cramps and uncontrollable muscle twitching.

Sensory Nerves; Damage to sensory nerves are typically associated with altered touch, temperature or pain.

Autonomic Nerves; Damage to autonomic nerves can be associated with activities that are not controlled consciously, such as breathing, the heart, thyroid function, and digestion, which can result in secondary complications secondary to excessive sweating, changes in blood pressure, inability to tolerate heat and gastrointestinal symptoms.

Thus injury to peripheral nerves can have various secondary complications, which can be significant and have long term effects dependant upon the classification of nerve injury.

Pain and Hypersensitivity

Significant pain can occur with peripheral nerve injury, particularly with nerve root avulsions, causing neuropathic pain. Severe pain can also potentially lead to complex regional pain syndrome, all of which can impact on rehabilitation.

Adequate pain control for rehabilitation is of paramount importance.

Altered Sensation

Peripheral nerve injury is often associated with significant changes in sensation, with numbness, burning sensation, tingling or total loss of sensation in the part of the body affected by the damaged nerve, which can increase the incidence of further secondary injuries as a result of this altered reduced sensation such as pressure ulcers, burns, and lacerations.

Pressure Ulcers

Pressure sore in patient with foot drop

Patients with decreased sensation as a result of a peripheral nerve injury are at increased risk of developing pressure ulcers, which can be harder to see on dark skin. A pressure ulcer is a localised injury to the skin and/or underlying tissue usually over a bony prominence, as a result of pressure, or pressure in combination with shear.  A pressure sore can develop in a few hours, but the results can last for many months and can cause significant loss of function and impairment. A number of contributing or confounding factors are associated with pressure ulcers, but the significance of these factors is yet to be elucidated. Tissue injury is related to both extrinsic and intrinsic factors.

• Extrinsic factors include pressure, shear, friction, immobility, and moisture.
• Intrinsic factors relate to the condition of the patient such as local infection, sepsis, decreased autonomic control, altered level of consciousness, increased age, vascular occlusive disease, anaemia, malnutrition, sensory loss, and contracture.

Keeping skin dry, regular position changes and regular skin checks (use a mirror if necessary) will help.

Read more here about the prevention and management of Pressure Ulcers

Burns and Lacerations

Burns and skin lacerations as a result of contact with hot surfaces or water, sharp surfaces or not using protective clothing, e.g. shoes are common with altered sensation following peripheral nerve injury.

Test water with the opposite, or sensate limb, and always wear covered, supportive shoes if foot sensation is reduced.

Delayed Healing

Peripheral nerve injury can have an impact on healing, and slow down the healing mechanisms of soft tissue. This can be further exacerbated by muscle weakness, which can impact on circulation of blood in distal limbs causing swelling and thus poor healing.

Swelling

As peripheral nerve injury causes motor impairment in extremities, it affects the muscle pump from distal aspect of limbs, particularly in sciatic nerve injury, which may lead to blood pooling in distal limbs when limbs are in gravity-dependent position. This may cause further neuropraxia as a result of increased compression of the nerve and increased pain.

Limb elevation and range of movement (passive, active assisted or active) can encourage movement of fluid and help with swelling.

Contracture and Deformity

Contractures result from a loss in the extensibility of the soft tissue structures-skin, ligaments, muscles, and joint capsules crossing joints, leading to restriction in joint mobility, causing joint stiffness, and later on the deformity. Contractures reduce joint mobility and restrict activities of daily living. They are also associated with pain, spasticity, sleep disturbances, and skin breakdown. Most often contractures affect the joints important to daily living: hips, knees, ankles, wrists, and shoulder, causing problems with dressing, eating, transferring, sleeping comfortably, using a wheelchair, or doing any tasks that require full joint movement. Problems in any of these areas can reduce a person's independence. If the joints of the affected muscles are not moved passively in daily basis, in long term, muscles shorten and joint become stiff causing contracture and deformities.

Neuroma

Neuromas are a non-cancerous thickening of nerve fibres made of non-conducting tissue that stops the signal from being sent along the nerve. Neuromas are thought to be formed when nerve regeneration is blocked by scar tissue, preventing further regeneration. Neuromas are a potential, limiting complication of nerve recovery which can cause pain or hypersensitivity; they usually do not develop until at least six weeks post-injury. Movement of adjacent tissues or direct application of pressure on neuromas often causes pain by stimulating the nerve enclosed by the neuroma.

Weakness

Involvement of motor nerve causes weakness of muscles supplied by that nerve. Muscle atrophy can be significantly seen in long term.

Psychological Stress

Physical weakness, pain and deformities can hamper the mental status of the person causing post traumatic stress disorder and depression in long term.