Central nervous system and peripheral nervous system

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Definition

Mononeuropathy is damage to a single nerve, which results in loss of movement, sensation, or other function of that nerve.

Causes

Mononeuropathy is due to damage to a nerve outside the brain and spinal cord (peripheral neuropathy).

Mononeuropathy is most often caused by injury. Diseases affecting the entire body (systemic disorders) can also cause isolated nerve damage.

Long-term pressure on a nerve due to swelling or injury can result in mononeuropathy. The covering of the nerve (myelin sheath) or part of the nerve cell (the axon) may be damaged. This damage slows or prevents signals from traveling through the damaged nerves.

Mononeuropathy may involve any part of the body. Some common forms of mononeuropathy include:

• Axillary nerve dysfunction (loss of movement or sensation in the shoulder)
• Common peroneal nerve dysfunction (loss of movement or sensation in the foot and leg)
• Cranial mononeuropathy III, IV, compression or diabetic type
• Cranial mononeuropathy VI (double vision)
• Cranial mononeuropathy VII (facial paralysis)
• Femoral nerve dysfunction (loss of movement or sensation in part of the leg)
• Median nerve dysfunction (carpal tunnel syndrome -- including numbness, tingling, weakness, or muscle damage in the hand and fingers)
  
• Radial nerve dysfunction (problems with movement in the arm and wrist and with sensation in the back of the arm or hand)
• Sciatic nerve dysfunction (problem with the muscles of the back of the knee and lower leg, and sensation to the back of the thigh, part of the lower leg, and sole of the foot)
• Ulnar nerve dysfunction (cubital tunnel syndrome -- including numbness, tingling, weakness of outer and underside of arm, palm, ring and little fingers)

Symptoms

Symptoms depend on the specific nerve affected, and may include:

• Loss of sensation
• Paralysis
• Tingling, burning, pain, abnormal sensations
• Weakness

Exams and Tests

Your health care provider will perform a physical exam and focus on the affected area. A detailed medical history is needed to determine the possible cause of the disorder.

Tests that may be done include:

• Electromyogram (EMG) to check the electrical activity in the muscles
• Nerve conduction tests (NCV) to check the speed of electrical activity in the nerves
• Nerve ultrasound to view the nerves
• X-ray, MRI or CT scan to get an overall view of the affected area
• Blood tests
• Nerve biopsy (in case of mononeuropathy due to vasculitis)
• CSF examination
• Skin biopsy

Treatment

The goal of treatment is to allow you to use the affected body part as much as possible.

Some medical conditions make nerves more prone to injury. For example, high blood pressure and diabetes can injure an artery, which can often affect a single nerve. So, the underlying condition should be treated.

Treatment options may include any of the following:

• Over the counter painkillers, such as anti-inflammatory medicines for mild pain
• Antidepressants, anticonvulsants, and similar medicines for chronic pain
• Injections of steroid medicines to reduce swelling and pressure on the nerve
• Surgery to relieve pressure on the nerve
• Physical therapy exercises to maintain muscle strength
• Braces, splints, or other devices to help with movement
• Transcutaneous electrical nerve stimulation (TENS) to improve nerve pain associated with diabetes

Outlook (Prognosis)

Mononeuropathy may be disabling and painful. If the cause of the nerve dysfunction can be found and successfully treated, a full recovery is possible in some cases.

Nerve pain may be uncomfortable and last for a long time.

Possible Complications

Complications may include:

• Deformity, loss of tissue mass
• Medicine side effects
• Repeated or unnoticed injury to the affected area due to lack of sensation

Prevention

Avoiding pressure or traumatic injury may prevent many forms of mononeuropathy. Treating conditions such as high blood pressure or diabetes also decreases the risk of developing the condition.

References

Katirji B. Disorders of peripheral nerves. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier;2022:chap 106.

National Institute of Neurological Disorders and Stroke website. Peripheral neuropathy. www.ninds.nih.gov/health-information/disorders/peripheral-neuropathy. Updated August 7, 2024. Accessed September 30, 2024.

Smith G, Shy ME. Peripheral neuropathies. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 388.