Peroneal Nerve Injury

Description, Causes and Risk Factors:

Partial or total inability to dorsiflex the foot, as a consequence of which the toes drag on the ground during walking unless a steppage gait is used; most often ultimately due to weakness of the dorsiflexor muscles of the foot (especially the tibialis anterior), but has many causes, including disorders of the central nervous system, motor unit, tendons, and bones. The peroneal nerve is a branch of the sciatic nerve that wraps around the fibular head ("funny bone") near the knee and then innervates muscles that lift the foot and toes. Damage to this nerve from injury (e.g., knee dislocation), or even surgery, may cause a peroneal nerve injury.

The common peroneal nerve (CPN) can be damaged in the course of complex biosseous fractures of the leg, sharp injuries or lacerations, severe adduction injuries and dislocations of the knee, and gunshot wounds. The CPN can also be inadvertently injured during knee surgery such as removal of ganglions or benign tumours.

Peroneal nerve injury may follow direct injury to the dorsiflexors. A few cases of rupture of the tibialis anterior tendon leading to foot drop and suspicion of peroneal nerve palsy have been reported. This subcutaneous tendon rupture usually occurs after a minor trauma with the foot in plantar flexion.

Compartment syndromes also may lead to peroneal nerve injury. These are surgical emergencies and are not associated only with fracture or acute trauma. March gangrene, a form of anterior compartment syndrome, is thought to be due to edema and small hemorrhages in the muscles of the anterior compartment occurring after strenuous activity in individuals not accustomed to it. Deep posterior compartment syndrome also may result in peroneal nerve injury as a late sequela due to resultant contracture formation.

Neurologic causes of peroneal nerve injury include mononeuropathies of the deep peroneal, common peroneal, or sciatic nerves. Lumbosacral plexopathy, lumbar radiculopathy, motor neuron disease, or parasagittal cortical or subcortical cerebral lesions also can manifest as foot drop. These lesions can be differentiated through clinical and electrodiagnostic examinations.

A common behavioral cause of peroneal nerve injury s habitual crossing of the legs. These cases typically resolve with discontinuation of the habit.

Peroneal nerve injury also may be seen as a combination of neurologic, muscular, and anatomic dysfunction. Charcot foot is one example.

Symptoms:

Symptoms of peroneal nerve injury (foot drop) may include:

Inability to point toes toward the body (dorsi flexion).

• Pain.

• Weakness.

• Numbness (on the shin or top of the foot).

• Loss of function of foot.

• High-stepping walk (called steppage gait or footdrop gait).

Diagnosis:

Proper diagnosis of peroneal nerve injury requires the expert attention of experienced neurologists and nerve specialists.

Diagnosis may include:

A comprehensive clinical exam, including neurological exams.

• Complete medical history.

• Electrical testing.

• Imaging studies, such as X-rays or high-resolution 3-T MRI (magnetic resonance imaging), and

• Electromyography (EMG) and nerve conduction studies measure electrical activity in the muscles and nerves. These tests can be uncomfortable, but they're very useful in determining the location of the damage along the affected nerve.

Diagnosis is necessary to determine the cause of peroneal nerve injury, so the appropriate treatment plan, including a surgical option, is considered.

Treatment:

Unfortunately, for uncertain reasons, the peroneal nerve has a poor chance of recovery, with or without surgery. The mainstay of early treatment is physical therapy and a properly fitting, custom-made orthotic (foot splint). This orthotic is unobtrusive, and usually allows a return to normal daily activity.

Specific treatment for peroneal nerve injury may include:

Braces or splints. A brace on your ankle and foot or splint that fits into your shoe can help hold your foot in a normal position.

• Physical therapy. Exercises that strengthen your leg muscles and help you maintain the range of motion in your knee and ankle may improve gait problems associated with foot drop. Stretching exercises are particularly important to prevent the development of stiffness in the heel.

• Nerve stimulation. Sometimes stimulating the nerve that lifts the foot improves foot drop.

• Surgery. In cases where foot drop is relatively new, nerve surgery may be helpful. If foot drop is long-standing, your doctor may suggest surgery that fuses ankle or foot bones or a procedure that transfers a functioning tendon to a different position.

Depending on the type of injury, surgery may be recommended immediately, or after waiting a few months. Surgical repair includes possible decompression, nerve suture, or nerve grafting. Other surgical options include nerve transfer and tendon transfer. A nerve transfer involves taking a branch from a less important lower leg muscle and connecting it to the muscle that lifts the foot. A tendon transfer involves taking a tendon that moves the foot inward, and connecting it to the top of the foot so that it now lifts the foot upward, thereby resolving the drop foot.

Because peroneal nerve injuries recover very poorly if too much time elapses before treatment, these patients should consider all their options before opting for a more conservative "wait and see" approach.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.