Peroneal Palsy

Peroneal palsy is a term used to describe the loss of motor function of the muscles supplied by the common peroneal nerve. Peroneal palsy is the result of chronic nerve compression at the head of the fibula (outside bone of the lower leg). The most common contributing causes to peroneal palsy are surprisingly benign, everyday activities. For instance, crossing the legs, left over right, would put pressure on the lateral aspect of the left leg, compressing the common peroneal nerve. If this activity is repeated throughout the day, there's a strong likelihood that the common peroneal nerve will become compressed and symptomatic. Another common contributing factor to peroneal palsy is associated with driving, and particularly in those who drive for a living. If the outer aspect of the knee rests against the door, compression of the common peroneal nerve can result in peroneal palsy. And lastly, peroneal palsy may occur following knee replacement surgery.

Diagnosis of peroneal palsy can be made clinically by use of a test called a Tinel's sign. A Tinel's sign is performed by taking two fingers and percussing the area where the common peroneal nerve crosses the fibula. This area can be found by palpating the head of the fibula, on the outside of the knee. The common peroneal nerve comes from behind the knee and passes over the fibula about 1 inch distal to the head. The image (right) outlines the course of the common peroneal nerve as it crosses the fibula. A Tinel's sign would be elicited at the level of the red dot in this image.  A positive Tinel's sign would result in a tingle down the anterior, lateral leg, along the distribution of the common peroneal nerve. Nerve conductions studies may also be used to measure delayed conduction of the common peroneal nerve. The sensitivity of nerve conduction velocity testing is not always high enough to confirm the presence of a nerve entrapment. Nerve conduction testing will only be positive in the most severe cases of peroneal palsy. MRI, x-ray, CT scan and bone scans are not effective in defining nerve entrapments like peroneal palsy and are therefore not used to diagnose this condition.

Treatment of peroneal palsy focuses on identification and elimination of contributing factors that may place chronic pressure on the common peroneal nerve (as described above). If elimination of these factors fails to decrease the symptoms of peroneal palsy, external neurolysis can be performed on the common peroneal nerve. External neurolysis, or nerve decompression, releases the deep fascia that surrounds the common peroneal nerve as it courses over the fibula. External neurolysis of the common peroneal nerve can be performed on and out-patient basis. General anesthesia is usually used along with a thigh tourniquet for hemostasis. The procedure takes approximately 20 minutes. Patients are able to walk on the leg the same day. Most patients return to normal activities in several weeks.

Head of the fibula - the most proximal aspect of the bone that runs from the outside of the knee to the outside of the ankle.  Palsy - to loose function, muscle tone and sensation, of a specific area of the body.

The common peroneal nerve is formed as a branch of the sciatic nerve behind the knee. As the common peroneal nerve leaves the popliteal space (the area behind the knee) it crosses the head of the fibula and descends the lateral leg.

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Initial symptoms of peroneal palsy include paresthesia (loss of sensation) of the lateral leg and foot. As the symptoms progress, motor function of the foot becomes effected. The tibialis anterior, peroneus brevis and peroneus longus muscles will be effected.  The ankle and foot will become weak, turning in and not being able to stabilize the foot as the body passes over it. Instability will occur with periodic ankle sprains.

Lumbar radiculopathy

Sciatica

• Peripheral Neuropathy

• Mortons Neuroma

• Tarsal Tunnel Syndrome

• Baxters Nerve Entrapment

• Diabetic Peripheral Neuropathy

This article was written by Jeffrey A. Oster, DPM and last updated 2/8/13. No additional information is available for this topic.