Femoral nerve dysfunction
Femoral nerve dysfunction is a loss of movement or sensation in the leg due to nerve damage.
See also: Peripheral neuropathy; Mononeuropathy; Mononeuritis multiplex
Neuropathy - femoral nerve; Femoral neuropathy
Causes, incidence, and risk factors
The femoral nerve is located in the leg. It supplies the muscles that help straighten the leg. It provides feeling (sensation) to the front of the thigh and part of the lower leg.
A nerve is made up of many fibers, called axons, surrounded by insulation, called the myelin sheath.
Damage to a nerve such as the femoral nerve is called mononeuropathy. Mononeuropathy usually means there is a local cause of the nerve damage, although disorders that involve the entire body (systemic disorders) can also cause isolated nerve damage (such as occurs with mononeuritis multiplex).
The usual causes of femoral nerve dysfunction are direct injury (trauma), prolonged pressure on the nerve, and compression of the nerve by nearby parts of the body or disease-related structures (such as a tumor). Prolonged pressure may lead to a lack of oxygen because there is decreased blood flow (ischemia) in the area. This lack of oxygen can cause further complications.
Entrapment involves pressure on the nerve where it passes through a narrow structure (for example, as it passes through a muscle). The damage includes destruction of the insulation around the nerve (the myelin sheath) or destruction of part of the fibers themselves (the axon). This damage slows or prevents nerve impulses from passing through the nerve.
The femoral nerve can be injured due to breaking bones of the pelvis. It can be injured when a catheter is placed in the artery in the groin (femoral artery), which lies next to the nerve. It can be one of many nerves affected by diseases causing widespread nerve damage (polyneuropathy), such as diabetes. It also can be damaged by pressure from tumors, abscesses, or internal bleeding into the pelvis or abdomen.
One common risk factor is lying on the back with the thighs and legs flexed ("lithotomy" position) during surgery or diagnostic procedures. Branches of the femoral nerve can be compressed by tight or heavy waist belts. In some cases, no cause can be found.
- Sensation changes in the thigh, knee, or leg, such as decreased sensation, numbness, tingling, burning, a feeling of the knee "giving way" or buckling, or (uncommonly) pain
- Weakness of the knee or leg, including difficulty going up and down stairs -- especially down
Signs and tests
An exam of the nerves and muscles (neuromuscular exam) of the legs shows that the femoral nerve is not working well. You might have weakness when you straighten the knee or bend at the hip. Sensation changes are located on the front of the thigh and inner calf. The knee reflex may be decreased or absent. The quadriceps muscles on the front of the thigh may be smaller than normal.
Tests that reveal femoral nerve dysfunction may include:
- Electromyography (EMG)
- Nerve conduction tests (NCV, usually done at the same time as an EMG)
- MRI to check for masses or abnormal tissue (lesions)
You'll have tests based on the suspected cause of the problem, which the doctor will base on your medical history, symptoms, and the pattern of symptom development. These tests may include various blood tests, x-rays, scans, or other tests.
Your doctor will try to identify and treat the cause of the nerve damage. In some cases, no treatment is required and you'll recover on your own. In that case, any treatment is aimed at increasing mobility and independence while you recover.
Supportive treatment is usually given if the symptoms come on suddenly, if there is only minor sensation or movement changes, no history of trauma to the area, and no sign that nerve function is getting worse.
Other treatments include:
- Corticosteroids injected into the area to control obvious swelling or inflammation.
- Pain medication, if necessary. Various other medications can reduce the stabbing pains that some people experience. The benefits of medications should be weighed against any possible side effects.
- Some people might benefit from surgical removal of tumors or other growths that press on the nerve.
Physical therapy may be helpful to maintain muscle strength. Orthopedic appliances such as braces or splints may help in walking. Your health care provider might recommend vocational counseling, occupational therapy, job changes or retraining, or similar interventions.
If the cause of the femoral nerve dysfunction can be identified and successfully treated, it is possible to recover fully. In some cases, there may be partial or complete loss of movement or sensation resulting in some degree of permanent disability.
Nerve pain may be quite uncomfortable and can continue for a long time. Injury to the femoral area may also injure the femoral artery or vein, which can cause bleeding and other problems.
When there is a loss of feeling (sensation), a potential complication is repeated and unnoticed injury to the leg. When there is muscle weakness, falls and related injuries may occur.
Calling your health care provider
Call your health care provider if you develop symptoms of femoral nerve dysfunction.
Prevention depends on the cause of the nerve damage.
Misulis KE. Lower back and lower limb pain. In: Bradley WG, Daroff RB, Fenichel GM, Jakovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann; 2008:chap 33.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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