Foot Drop/Common Peroneal Nerves

Foot Drop

Common peroneal nerve dysfunction is damage to the peroneal nerve leading to loss of movement or sensation in the foot and leg.

Causes

The peroneal nerve is a branch of the sciatic nerve, which supplies movement and sensation to the lower leg, foot and toes. Common peroneal nerve dysfunction is a type of peripheral neuropathy (damage to nerves outside the brain or spinal cord). This condition can affect people of any age.

Dysfunction of a single nerve, such as the common peroneal nerve, is called a mononeuropathy. Mononeuropathy means the nerve damage occurred in one area. However, certain body-wide conditions may also cause single nerve injuries.

Damage to the nerve destroys the myelin sheath that covers the axon (branch of the nerve cell). Or it may destroy the whole nerve cell. There is a loss of feeling, muscle control, muscle tone, and eventual loss of muscle mass because the nerves aren’t stimulating the muscles.

Common causes of damage to the peroneal nerve include the following:

Trauma or injury to the knee
Fracture of the fibula (a bone of the lower leg)
Use of a tight plaster cast (or other long-term constriction) of the lower leg
Crossing the legs regularly
Regularly wearing high boots
Pressure to the knee from positions during deep sleep or coma
Injury during knee surgery or from being placed in an awkward position during anesthesia

Common peroneal nerve injury is more common in people:

Who are very thin (for example, from anorexia nervosa)
Who have conditions such as diabetic neuropathy or polyarteritis nodosa
Who are exposed to certain toxins that can damage the common peroneal nerve

Charcot-Marie-Tooth disease is an inherited disorder that affects all of the nerves. Peroneal nerve dysfunction occurs early in this disorder.

Symptoms

Decreased sensation, numbness, or tingling in the top of the foot or the outer part of the upper or lower leg
Foot that drops (unable to hold the foot up)
“Slapping” gait (walking pattern in which each step makes a slapping noise)
Toes drag while walking
Walking problems
Weakness of the ankles or feet

Exams and Tests

Examination of the legs may show:

Loss of muscle control in the lower legs and feet
Atrophy of the foot or foreleg muscles
Difficulty lifting up the foot and toes and making toe-out movements

Tests of nerve activity include

Electromyography (EMG, a test of electrical activity in muscles)
Nerve conduction tests
MRI
Nerve ultrasound

What other tests are done depend on the suspected cause of nerve dysfunction, and the person’s symptoms and how they developed. Tests may include blood tests, x-rays and scans.

Treatment

Treatment aims to improve mobility and independence. Any illness or other cause of the neuropathy should be treated. Padding the knee may prevent further injury by crossing the legs and remind you to not cross your legs.

Corticosteroids injected into the area may reduce swelling and pressure on the nerve in some cases.

You may need surgery if:

The disorder does not go away
You have problems with movement
There is evidence that the nerve axon is damaged

Surgery to relieve pressure on the nerve may reduce symptoms if the disorder is caused by pressure on the nerve. Surgery to remove tumors on the nerve may also help.

CONTROLLING SYMPTOMS

You may need over-the-counter or prescription pain relievers to control pain. Other medications may be used to reduce pain include gabapentin, carbamazepine, or tricyclic antidepressants such as amitriptyline. Whenever possible, avoid or limit the use of medication to reduce the risk of side effects.

If your pain is severe, a pain specialist can help you explore all options for pain relief.

Physical therapy exercises may help you maintain muscle strength.

Orthopedic devices may improve your ability to walk and prevent contractures. These may include braces, splints, orthopedic shoes, or other equipment.

Vocational counseling, occupational therapy, or similar programs may help you maximize your mobility and independence.

Outlook (Prognosis)

The outcome depends on the cause of the problem. Successfully treating the cause may relieve the dysfunction, although it may take several months for the nerve to grow back.

However, if nerve damage is severe, disability may be permanent. The nerve pain may be very uncomfortable. This disorder does NOT usually shorten a person’s expected lifespan.

Possible Complications

Decreased ability to walk
Permanent decrease in sensation in the legs or feet
Permanent weakness or paralysis in the legs or feet
Side effects of medication

When to Contact a Medical Professional

Call your health care provider if you have symptoms of common peroneal nerve dysfunction.

Prevention

Avoid putting long-term pressure on the back or side of the knee. Treat injuries to the leg or knee right away.

If a cast, splint, dressing, or other pressure on the lower leg causes a tight feeling or numbness, call your health care provider.

Alternative Names

Neuropathy – common peroneal nerve; Peroneal nerve injury; Peroneal nerve palsy

References

King JC. Peroneal neuropathy. In: Frontera WR, Silver JK, Rizzo TD, eds. Essentials of Physical Medicine and Rehabilitation: Musculoskeletal disorders, pain and rehabilitation. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 66.

Update Date: 9/25/2013

Updated by: Joseph V. Campellone, MD, Department of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

From http://www.nlm.nih.gov/medlineplus/ency/article/000791.html

Foot Drop