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Zenker’s paralysis, also known as peroneal nerve paralysis or palsy, is a paralysis on common fibular nerve that affects patient’s ability to lift the foot at the ankle. The condition was named by Friedrich Albert von Zenker. Peroneal nerve paralysis usually leads to neuromuscular disorder, peroneal nerve injury or foot drop, which can be a symptom of more serious disorders such as nerve compression. The origin of peroneal nerve palsy has been reported due to injury associated with musculoskeletal injury or isolated nerve traction and compression. Also it has been reported due to mass lesions and metabolic syndromes. Peroneal nerve is most commonly interrupted at the knee and possibly at the hip and ankle as well. Most studies reported that about 30% peroneal nerve palsy following from knee dislocations.

Peroneal nerve injury occurs when the knee is exposed to varus stress. It occurs when the posterolateral corner structure of knee is injured. Relatively tethered location around fibular head, tenuous vascular supply and epineural connective tissues are possible factors that predispose the common peroneal nerve to injury. Treatment options for nerve palsy include both operative and non-operative techniques. Initial treatment includes physical therapy and ankle-foot orthosis. Physical therapy mainly focuses on preventing deformation by stretching the posterior ankle capsule. A special brace or splint worn inside the shoe (called an Ankle Foot Orthosis) may be used to hold the foot in the best position for walking. Orthosis stretches posterior ankle structures. Physical therapy can help you learn to walk with a foot drop. This condition may improve when nerve compression is relieved.

Operative treatment techniques include neurolysis grafting and tendon transfer. Neurolysis grafting results depend on nerve graft length with recovery rates of about 44% for nerve grafts longer than 6cm. Furthermore, patients able to perform activities more strenuous than walking have not been reported which means the results were not satisfiable. Posterior tendon transfer succeeded in allowing patients to return to ambulation without assistive devices. Unlike neurolysis grafting, tendon transfer allowed 10 out of 12 patients to no longer require orthosis. However, dorsiflexion strength on injured side of knee was only 30% of strength on normal side. Even though transfer restored the balance to foot dorsiflexion, it could lead to flatfoot or hindfoot valgus. Peroneal nerve palsy leads to significant functional impairment and further dysfunctions after knee dislocation. Treatment strategies for restoring dorsiflexion and peroneal nerve function have given poor results in outcome. Further development and experiments on surgical techniques are required to treat peroneal nerve palsy.

Usually, electromyography is used to observe peroneal nerve palsy within one month of injuries. And if it is partial peroneal nerve palsy, patients have higher chance to recover fully from the palsy. More than 70 to 80 percent of patients with partial paralysis recovered completely, but those with complete paralysis have chances less than 30 percent to recover completely. If the symptom does not get any better in few months, surgery is required to decompress the nerve compression. Surgical operations are such as grafting and tendon transfer. Tendon transfers have higher chance to treat nerve palsy, and such transfers include posterior, anterior, and anteroposterior tibial tendon transfer. Peroneal nerve and its nerve branches need to be fixed from adherence to proximal fibula, which proximal fibula is about 3~5cm.

Albert Von Zenker


Friedrich Albert von Zenker (1825 – 1898) was a German pathologist and physician, celebrated for his discovery of trichinosis. He was born in Dresden, and was educated in Leipzig and Heidelberg. Attached to the city hospital of Dresden in 1851, he added, in 1855, the duties of professor of pathological anatomy and general pathology in the surgico-medical academy of that city. In 1862 he became professor of pathological anatomy and pharmacology at Erlangen. Three years afterwards he assumed with Ziemssen the editorship of the Deutsches Archiv für klinische Medizin. In 1895 he retired from active service. His important discovery of the danger of trichine dates from 1860. In that year he published "Ueber die Trichinenkrankheit des Menschen" (in volume xviii of Virchow's Archiv). Beside, Zenker also found Zenker's degeneration and Zenker's diverticulum

Causes
Causing factors of peroneal nerve palsy are such as musculoskeletal injuries or peroneal nerve injuries. Usually the paralysis occurs outside of the leg and top of the foot. Palsy causes decrease of muscle strengths for lifting the foot, twisting ankle outside, and moving toes around. Major cause of palsy is due to dislocation of knee from any injuries related to knee. Other possible causing factors are metabolic dysfunction to lower part of knee or disorientation of hip or pelvis. Damages on peroneal nerves destroy the myelin sheath that covers the axon or may destroy the whole nerve cell. There might be a loss of feeling, muscle control, muscle tone, and eventual loss of muscle mass because the nerves aren't stimulating the muscles after damaged. 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 bodywide conditions may also cause single nerve injuries.

Common causes of damage to the peroneal nerve include the following:
 * Traumatic injury on the knee
 * Fracture of the fibula
 * 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
 * Long periods of resting on bed
 * Broken leg bone

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

Prolonged pressure on nerve may occur because of:
 * sitting position
 * Blood clots, tumors
 * Casts on lower leg due to tightness

Symptoms
Symptoms of peroneal nerve palsy are related to mostly lower legs and foot which are the followings: 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.
 * Decreased sensation, numbness, or tingling in the top of the foot or the outer part of the upper or lower leg
 * Foot drops (unable to hold the foot straight across)
 * Slapping gait (walking pattern in which each step makes a slapping noise)
 * Toes drag while walking
 * Weakness of the ankles or feet
 * Prickling sensation
 * Pain in shin
 * Pins and needles sensation

Diagnosis
For partial nerve palsy, more than 80% will recover completely. For complete nerve palsy, less than 40% will have complete recovery. Peroneal nerve in continuity arises from defined etiology will be recovered better than ones arises from idiopathic causes.

Exams required for following reasons:
 * Consider lumbar radiculopathy during the examination
 * May be an obvious foot drop
 * Sensory loss may be difficult to determine because of variable & small autonomous zone of sensation
 * Tinel's sign over the fibular neck, helps localize the site of nerve compression
 * Check for a fabella and check to see if direct compression reproduces nerve symptoms
 * In cases of knee dislocation it is important to test for function of the tibial branch of the sciatic nerve as well
 * In some cases of peroneal nerve avulsion, there will also be a sciatic nerve traction injury

Electromyography
Electromyography is used to observe peroneal nerve palsy within one month of injuries. And if it is partial peroneal nerve palsy, patients have higher chance to recover fully from the palsy. More than 70 to 80 percent of patients with partial paralysis recovered completely, but those with complete paralysis have chances less than 30 percent to recover completely. If the symptom does not get any better in few months, surgery is required to decompress the nerve compression.

Nerve conduction velocity
Nerve conduction velocity is an important aspect of nerve conduction studies. It is the speed at which an electrochemical impulse propagates down a neural pathway. Conduction velocities are affected by a wide array of factors, including age, sex, and various medical conditions. Studies allow for better diagnoses of various neuropathies, especially demyelinating conditions as these conditions result in reduced or non-existent conduction velocities. To perform nerve conduction velocity, surface electrodes are placed onto the skin over nerves at various locations. Each patch sends electrical impulses which stimulates the nerve. Resulting electrical activity of nerve is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to determine the velocity of the nerve signals.

MRI
An MRI (magnetic resonance imaging) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not use radiation. Single MRI images are called slices. The images can be stored on a computer or printed on film. One exam produces dozens or sometimes hundreds of images. To locate nerve palsy, MRI is used by physicians to detect the position and location of damaged peroneal nerve.

Treatments
Precise knowledge about the length and exact localization of a damaged nerve segment is essential for surgical intervention. On one hand, certain preoperative information about the overall state of an injured nerve (state of the neural and perineural tissue) is important because exploratory inspection of a nerve itself may lead to additional inadvertent damage. If, on the other hand, the surgeon, during genicular ligament reconstruction, inspects a nerve at the site of most probable injury only (limited neurolysis), he or she may sometimes by chance expose an unaffected section of a nerve. Because of the mechanism of nerve injury during traction, however, a more proximal or distal segment of the nerve may be severely damaged. A limited nerve inspection without preoperative knowledge about the site of nerve injury may thus give the false impression of an unimpaired nerve and wrongly lead to conservative treatment of the nerve lesion. If no neurologic improvement is shown after 2-3 months from injuries, then operative decompression is indicated. Surgical operations such as grafting and tendon transfer are necessarily required.

Tendon transfer
Many different conditions can be treated by tendon transfer surgery. Tendon transfer surgery is necessary when a certain muscle function is lost because of a nerve injury. If a nerve is injured and cannot be repaired, then the nerve no longer sends signals to certain muscles. Those muscles are paralyzed and their muscle function is lost. Tendon transfer surgery can be used to attempt to replace that function. Common nerve injuries that are treated with tendon transfer surgery are spinal cord, radial nerve, ulnar nerve, or median nerve injury. Tendon transfers have higher chance to treat nerve palsy, and such transfers include posterior, anterior, and anteroposterior tibial tendon transfer. Peroneal nerve and its nerve branches need to be fixed from adherence to proximal fibula, which proximal fibula is about 3~5cm.

Tendon graft
Graft is a surgical procedure to move tissue from one site to another on the body, or from another person, without bringing its own blood supply with it. Instead, a new blood supply grows in after it is placed. A similar technique where tissue is transferred with the blood supply intact is called a flap. In some instances a graft can be an artificially manufactured device. Examples of this are a tube to carry blood flow across a defect or from an artery to a vein for use in hemodialysis.

Arthroplasty
Arthroplasty on knee has been broadly used to treat knee and musculoskeletal joint dislocation. It is an elective procedure that is done to relieve pain and restore function to the joint after damage by arthritis or some other type of trauma. However, there has been series of reports arthroplasty worsens condition of peroneal nerve, causing paralysis. Other forms of arthroplasty include resection(al) arthroplasty, resurfacing arthroplasty, mold arthroplasty, cup arthroplasty, silicone replacement arthroplasty, etc.

Prevention
Avoid putting long-term pressure ono 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.


 * Avoid crossing legs
 * Move around actively and frequently
 * Wear knee protections if you work on knee
 * Alert physician if feeling numbness on leg when casted