Friedrich's ataxia

Definition

Friedrich’s ataxia is one of a group of disorders in which there is degeneration of the nerves in the spinal cord, the part of the brain called the cerebellum, and of sensory nerves to the hands and feet. The result of this degeneration is weakness, unsteady movement, loss of sensation, and a variety of other problems discussed below.

"Ataxia" is the term used to describe the shaky movements and unsteady gait that result when the brain is not regulating the body’s posture and the strength and direction of limb movements. It can be due to disease of the cerebellum or of the nerves involved in sensation.

Friedrich’s ataxia, the classic form of hereditary ataxia, was first clearly described by Nikolaus Friedrich of Heidelberg in 1863. It is usually recognizable to a neurologist (a specialist in diseases of the nervous system), but specialized genetic tests are sometimes needed to distinguish Friedrich’s from some of the other, rarer ataxic diseases.

It is usually a recessive disorder, meaning that the affected person has inherited two genes for the disorder, one from each parent. Often the affected person is the only such individual in a family, as the disorder involves a rare abnormality on Chromosome 9.

Symptoms and signs

The disorder usually occurs between the ages of five and 15 (often at the onset of puberty), and is first apparent in the legs. The previously healthy child begins to stagger and lurch while walking and is unsteady while standing – this is referred to as ataxia. Later, the child becomes clumsy when using the hands and arms. Speech becomes clumsy as well, and words are indistinct, although the content and meaning are normal. There is often curvature of the spine (scoliosis) and bony abnormalities of the feet and toes.

Several other features may become apparent to a physician conducting a careful examination: jerkiness of the eyes (nystagmus); poor co-ordination, weakness of the limbs; a loss of normal reflexes, and the appearance of others not normally present (e.g. ‘the Babinski reflex’, in which the big toe turns upwards when the sole of the foot is stimulated); and a loss of sensation in the hands and feet.

In general, intelligence and mental ability is preserved.

Friedrich’s ataxia is usually, but not always, a progressive condition, with a worsening of symptoms through the twenties into the thirties. Death usually occurs in the third decade, and is most often due to the heart failure that is also a feature of the condition.

It should be recognized that there is a spectrum of severity, and that in rare cases, the person shows a very mild form of the disorder involving only the foot deformities or absent reflexes. In these cases there is little disability or progression. Such mild cases are most likely to be seen in family members of a person who has the fully developed syndrome.

Diagnosis

Any child who starts developing worsening clumsiness and difficulty walking or using their hands should be referred to a physician for assessment. Freidrich's ataxia is suspected particularly where there is a family history, and where there are spine or foot deformities. A neurologist will be able to distinguish Freidrich’s ataxia from the many other possible diseases that also produce clumsiness and weakness, and the diagnosis, when suspected, can be confirmed with specialized genetic blood tests.

Treatment

While there is no specific treatment available, supportive measures to maintain good general health are vital. Physical and occupational therapy can help improve mobility and quality of life.

Outcome

Survival beyond early adulthood is rare. Death is often associated with a form of cardiomyopathy – a disorder of the heart muscle.

When to call the doctor

If you have a family history of any of the degenerative diseases affecting the spine and the cerebellum you should see your doctor to arrange for genetic counselling.

Reviewed by Dr Andrew Rose-Innes, Neurology Division, The Oregon Clinic, Portland Oregon