Hereditary peroneal nerve dysfunction

Alternative names
Progressive neuropathic (peroneal) muscular atrophy; Charcot-Marie-Tooth disease; Neuropathy - peroneal (hereditary); Hereditary motor and sensory neuropathy

Definition
Charcot-Marie-Tooth disease defines a group of inherited, slowly progressive disorders that result from progressive damage to nerves. Symptoms include numbness and wasting of muscle tissue, first in the feet and legs, then in the hands and arms.

Causes, incidence, and risk factors

Charcot-Marie-Tooth diseases involve damage to nerves (neuropathy), usually from loss of the electrical insulation (myelin) around nerve fibers. All nerves are affected, but motor nerves (the nerves that stimulate movement) are most severely affected.

The nerves in the legs are affected first and most severely. Symptoms usually begin between mid-childhood and early adulthood. The disorder is inherited, with autosomal dominant, autosomal recessive as well as X-linked recessive inheritance patterns. At least four genes have been discovered to be the cause of this group of diseases.

Charcot-Marie-Tooth disease causes destruction of the myelin sheath in some people. In other people, the central (axon) portion of the nerve cell degenerates.

The disorder most commonly affects the nerves to the feet and legs, most significantly the peroneal nerve. The damage is slowly progressive, usually beginning with foot drop and progressing up the legs. There is a loss of muscle control and muscle tone, and eventual loss of muscle mass caused by lack of nervous stimulation to the muscles.

Symptoms

     
  • Weakness (decreased muscle strength) of the hips, legs, or feet  
  • “Slapping” gait (the feet hit the floor hard when walking)  
  • Foot drop (inability to hold foot horizontal)  
  • Foot deformity (very high arch to feet)  
  • Progressive leg deformity  
  • “Stork leg” appearance (loss of lower leg muscle mass leading to skinny calves)  
  • Numbness in the foot or leg

Later, similar symptoms may appear in the arms and hands. This includes hand deformities. (The hand develops a claw-like shape.)

Signs and tests
An examination by touch may reveal thickened nerve bundles under the skin of the legs in the demyelinating form of Charcot-Marie-Tooth disease. The stretch reflexes in the legs are absent. There is loss of muscle control and atrophy in the foot or leg. There is difficulty with lifting up the foot (dorsiflexion) and with toe-out movements (eversion).

     
  • A muscle biopsy or nerve biopsy may confirm the diagnosis.  
  • Nerve conduction tests are often performed to distinguish axonal from demyelinating forms of the disorder.  
  • Genetic testing is available for most forms of the disease.

Treatment
There is no known cure for Charcot-Marie-Tooth disease. Treatment is aimed at maximizing independence. Orthopedic surgery or equipment (such as braces or orthopedic shoes) may make it easier to walk.

Vocational counseling, occupational therapy, or physical therapy may be appropriate for some people to help maintain muscle strength and maximize independent functioning.

Expectations (prognosis)
Charcot-Marie-Tooth disease is slowly progressive, eventually causing disability. It is not life-threatening. It is not usually painful, but there may be numbness in the area.

Complications

     
  • Progressive inability to walk  
  • Progressive weakness  
  • Injury to areas of the body that have decreased sensation

Calling your health care provider
Call for an appointment with your health care provider if there is persistent weakness or decreased sensation in the feet or legs.

Prevention
Genetic counseling and testing is advised if there is a strong family history of the disorder.

Johns Hopkins patient information

Last revised: December 2, 2012
by Arthur A. Poghosian, M.D.

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