Mononeuropathy

Definition

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

Alternative Names

Neuropathy; Isolated mononeuritis

Causes

Mononeuropathy is a type of damage to nerves outside the brain and spinal cord (peripheral neuropathy).

Mononeuropathy is most often caused by injury, although body-wide (systemic) disorders may 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 of the common forms of mononeuropathy include:

• Axillary nerve dysfunction
• Common peroneal nerve dysfunction
• Carpal tunnel syndrome (median nerve dysfunction)
• Cranial mononeuropathy III; compression type
• Cranial mononeuropathy III; diabetic type
• Cranial mononeuropathy VI
• Cranial mononeuropathy VII (facial paralysis)
• Femoral nerve dysfunction
• Radial nerve dysfunction
• Sciatic nerve dysfunction (sciatica)
• Ulnar nerve dysfunction (cubital tunnel syndrome)

Symptoms

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

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

Exams and Tests

A detailed medical history is needed to determine the possible cause of the disorder. An examination and nerve and muscle testing may show a loss of feeling, movement, or other problems with a specific nerve. Reflexes may be abnormal.

Tests may include:

• Electromyogram (EMG) -- a recording of electrical activity in muscles
• Nerve conduction tests (NCV) -- recording the speed of electrical activity in the nerves
• Nerve biopsy
• Nerve ultrasound
• MRI

Other tests may include:

• Antinuclear antibody panel (ANA)
• Blood chemistry tests
• C-reactive protein
• Imaging scans, such as MRI or CT scan
• Rheumatoid factor
• Sedimentation rate
• Thyroid tests
• X-rays

Treatment

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

The cause of the mononeuropathy should be identified and treated as appropriate. Sometimes, no treatment is needed and you will get better on your own.

High blood pressure and diabetes can injure an artery, which can often affect a single nerve. The underlying condition should be treated.

Corticosteroids injected into the area may reduce swelling and pressure on the nerve if it is being pinched or trapped against another part of the body, such as a bone. Surgery may be recommended if symptoms are caused by entrapment of the nerve. Surgery to relieve the pressure on the nerve may help in some cases.

Medications:

• Over-the-counter or prescription pain medicine may be needed to control pain (neuralgia).
• Prescription medications such as gabapentin, pregabalin, phenytoin, carbamazepine, or antidepressants such as amitriptyline, nortriptyline, or duloxetine may be used to reduce stabbing pains. Whenever possible, avoid or minimize the use of these drugs to reduce the risk of medication side effects.

Other Treatments:

• Physical therapy exercises to maintain muscle strength
• Orthopedic braces, splints, or other appliances
• Vocational counseling, occupational therapy, occupational changes, job retraining

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 and even likely in some cases.

The amount of disability varies from no disability to partial or complete loss of movement or sensation. Nerve pain may be uncomfortable and may last for a long time.

Possible Complications

• Deformity, loss of tissue mass
• Medication 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 your risk of developing the condition.

References

Katirji B, Koontz D. Disorders of peripheral nerves. In:Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley’s Neurology in Clinical Practice. 6th ed. Philadelphia, Pa: Saunders Elsevier; 2012:chap 76.

Shy ME. Peripheral neuropathies. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 428.

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