Neuropathy - femoral nerve

Alternative names
Femoral nerve dysfunction

Definition
Femoral nerve dysfunction is a loss of movement or sensation in the leg (peripheral neuropathy) caused by damage to the femoral nerve.

Causes, incidence, and risk factors

The femoral nerve is located in the leg and supplies the muscles that help straighten the leg. It supplies sensation to the front of the thigh and part of the lower leg.

Dysfunction of a single nerve group such as the femoral nerve is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage (such as occurs with mononeuritis multiplex).

The usual causes are direct trauma, prolonged pressure on the nerve, and compression of the nerve by nearby body structures or pathologic structures (such as a tumor). Prolonged pressure may be complicated by ischemia (lack of oxygen from decreased blood flow) in the area.

Entrapment involves pressure on the nerve where it passes through a narrow structure. The damage includes destruction of the myelin sheath of the nerve or destruction of part of the nerve cell (the axon). This damage slows or prevents passage of impulses through the nerve.

The femoral nerve can be injured as a result of pelvic fractures. It may be injured during catheterization of the femoral artery. It can be affected by systemic diseases causing polyneuropathy (damage to multiple nerves) such as diabetes mellitus or polyarteritis nodosa. It can be damaged by pressure from lesions such as tumor, abscess, or internal bleeding into the pelvis or abdomen.

One common risk factor is lying in the “lithotomy” position (on the back with thighs and legs flexed) during surgery or diagnostic procedures. In some cases, no detectable cause can be identified.

Symptoms

     
  • Weakness of the knee or leg, including difficulty going up and down stairs - especially down.  
  • Sensation changes in the thigh, knee, or leg, such as decreased sensation, numbness, tingling, burning, a feeling of the knee “giving way,” or (uncommonly) pain.

Signs and tests
A neuromuscular examination of the legs indicates femoral nerve dysfunction. There may be weakness on straightening the knee or bending at the hip. Sensation changes are located on the front upper thigh and inner calf. The knee jerk reflex may be abnormal. There may be atrophy (loss of muscle mass) of the quadriceps muscles of the front of the thigh.

Tests that reveal femoral nerve dysfunction may include:

     
  • An EMG (a recording of electrical activity in muscles)  
  • Nerve conduction tests  
  • An MRI to check for masses or lesions

Tests are given based on the suspected cause of the dysfunction suggested by the patient’s history, symptoms, and pattern of symptom development. They may include various blood tests, x-rays, scans, or other tests.

Treatment

Treatment is aimed at increasing mobility and independence. The cause of the damage should be identified and treated if necessary. In some cases, no treatment is required and recovery is spontaneous.

Conservative treatment is given if there is sudden onset of symptoms, minimal sensation or movement changes, no history of trauma to the area, and no evidence of nerve degeneration.

Corticosteroids injected into the area may reduce swelling and pressure on the nerve in some cases. Pain medication may be needed to control symptoms. Various other medications (phenytoin, carbamazepine, gabapentin or tricyclic antidepressants such as amitriptyline) may reduce the stabbing pains that some people experience. Whenever possible, medication use should be avoided or reduced to lessen the risk of side effects.

Surgical removal of lesions that press on the nerve may benefit some cases.

Physical therapy may be helpful to maintain muscle strength. Orthopedic appliances such as braces or splints may aid in walking. Vocational counseling, occupational therapy, job changes or retraining, or similar interventions may be recommended.

Expectations (prognosis)
If the cause of the femoral nerve dysfunction can be identified and successfully treated, there is a possibility of full recovery. In some cases, there may be partial or complete loss of movement or sensation resulting in some degreeof disability. Nerve pain may be quite uncomfortable and persist for a long period of time. Trauma to the femoral area may also injure the femoral artery, which can cause fatal hemorrhage.

Complications
A complication is a recurrent or an unnoticed injury to the leg.

Calling your health care provider
Call your health care provider if symptoms of femoral nerve dysfunction develop.

Prevention
The prevention is variable depending on the cause of the nerve damage.

Johns Hopkins patient information

Last revised: December 3, 2012
by Martin A. Harms, M.D.

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