Friedreich’s ataxia

Alternative names
Spinocerebellar degeneration

Definition
Friedreich’s ataxia is an inherited form of progressive dysfunction of the cerebellum (the part of the brain responsible for movement and complex behavior), spinal cord, and peripheral nerves.

Causes, incidence, and risk factors

Friedreich’s ataxia is an autosomal recessive condition, which means that a person must inherit the defective gene from both parents in order to be affected. It is a polyneuropathy, which means that there is damage to multiple nerves

The condition affects 1 in 50,000 people. Symptoms are caused by degeneration of structures in the cerebellum and spinal cord responsible for coordination, muscle movement, and some sensory functions. Vision, particularly color vision, is often mildly affected. Hearing loss occurs in about 10% of patients.

Symptoms generally begin in childhood before puberty. Early symptoms include an unsteady gait, changes in speech, loss of reflexes, and jerky eye movements.

Abnormal muscle control and tone lead to spinal changes and scoliosis, or kyphoscoliosis may develop. Individuals with Friedreich’s ataxia may also have hammer toe and high arches.

Heart disease usually develops and may progress into heart failure. Death may result from heart failure or dysrhythmias that will not respond to treatment. Diabetes may develop in later stages of the disease in up to one third of patients.

Friedreich’s ataxia results from lack of a specific protein (frataxin) in cells of the brain, nerves, heart, and pancreas. The gene encoding this protein is susceptible to a particular kind of DNA mutation called triplet repeat expansion. What happens is that a sequence of three DNA “letters” is copied more times than is needed, and typically each time the disease is passed on, the number of repeats increases and the symptoms start earlier and become more severe. It is easily and reliably tested for in patient DNA from a blood sample.

Symptoms

     
  • Unsteady gait and uncoordinated movements (ataxia) that gets progressively worse  
  • Loss of coordination and balance; frequent falls or falling more than usual  
  • Jerky eye movements  
  • Abnormal speech  
  • Clumsiness, difficulty controlling the hands  
  • Muscle weakness (decreased muscle strength, independent of exercise)       o Legs, arms, or other parts of the body       o May progress to paralysis  
  • Difficulty getting out of a chair or climbing stairs (hip or pelvis weakness)  
  • Deformity of the spine or feet  
  • Muscle tremors, shakiness  
  • Numbness, sensory changes  
  • Dizziness  
  • Difficulty speaking clearly, abnormal speech rhythm  
  • Excessive thirst, urination or hunger (associated with diabetes)

Note: The intellect is normal.

Signs and tests
The doctor will look for the following signs:

     
  • Absent deep tendon reflexes  
  • Decreased or lost vibratory sense  
  • Decreased positional sense  
  • Kyphoscoliosis  
  • High arches  
  • Hammer toe  
  • Hypertrophic cardiomyopathy  
  • Congestive heart failure  
  • Diabetes  
  • Degeneration of the back of the eye (retina) is a rare sign  
  • Hearing loss

The following tests may be performed:

     
  • ECG  
  • Genetic testing for the frataxin gene  
  • X-ray of the chest  
  • X-ray of the spine  
  • Electrophysiologic studies  
  • EMG (electromyography)  
  • Nerve conduction tests  
  • Muscle biopsy  
  • X-ray, CT scan, or MRI of the head

Treatment

There is no known cure for Friedreich’s ataxia. The goal of treatment is to control symptoms and maintain general health. Physical activity is encouraged, and physical therapy may be beneficial.

As the disease may be associated with free radical damage to cells, antioxidants such as Vitamin E and coenzyme Q10 are frequently prescribed. There is no systematic scientific evidence of the efficacy of these supplements. Research is ongoing on the use of a coenzyme Q10 derivative (idebonone) in Friedreich ataxia. In preliminary trials, it slowed the development of heart failure in a small number of patients.

Safety must be considered when there is loss of balance or sensation. Safety railings, walkers, or other appliances may help. If the person loses feeling in a body part, injuries can be prevented by testing bath water to prevent burns, visually inspecting the body part to check for injuries, using protective shoes and helmets, and other measures.

Support Groups
Additional resources are available from the Friedreich’s Ataxia Research Alliance (http://www.frda.org).

Expectations (prognosis)
This is a life-shortening disorder and currently there is no cure. Most patients will be confined to a wheelchair by young adulthood. Most also develop untreatable Heart failure or arrhythmias, which shortens the life expectancy. Up to one third of patients develop diabetes, which responds to diabetes treatment.

Complications

     
  • Repeated or unnoticed injury  
  • Progressive disability  
  • Heart failure

Calling your health care provider
Call your health care provider if muscle weakness, numbness, loss of coordination, loss of reflexes, or other symptoms of Friedreich’s ataxia occur (particularly if there is a family history of the disorder).

Prevention
Genetic counseling and testing are recommended for prospective parents with a family history of Friedreich’s ataxia.

Johns Hopkins patient information

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

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