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By Mayo Clinic staff

Damage, degeneration or loss of nerve cells in the part of your brain that controls muscle coordination (cerebellum), results in loss of coordination or ataxia. Your cerebellum comprises two pingpong-ball-sized portions of folded tissue situated at the base of your brain near your brainstem. The right side of your cerebellum controls coordination on the right side of your body; the left side of your cerebellum controls coordination on the left side of your body.

Diseases that damage the spinal cord and peripheral nerves that connect your cerebellum to your muscles also may cause ataxia. Ataxia causes include:

• Head trauma. Damage to your brain or spinal cord from a blow to your head, such as might occur in a car accident, can cause sudden-onset ataxia, also known as acute cerebellar ataxia.
• Stroke. When the blood supply to a part of your brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients, brain cells begin to die.
• Transient ischemic attack (TIA). Caused by a temporary decrease in blood supply to part of your brain, most TIAs last only a few minutes. Loss of coordination and other signs and symptoms of a TIA are temporary.
• Cerebral palsy. This is a general term for a group of disorders caused by damage to a child's brain during early development — before, during or shortly after birth — that affects the child's ability to coordinate body movements.
• Multiple sclerosis (MS). MS is a chronic, potentially debilitating disease that affects your central nervous system, which comprises your brain and spinal cord.
• Chickenpox. Ataxia can be an uncommon complication of chickenpox and other viral infections. It may appear in the healing stages of the infection and last for days or weeks. Normally, the ataxia resolves completely over time.
• Paraneoplastic syndromes. These are rare, degenerative disorders triggered by your immune system's response to a cancerous tumor (neoplasm), most commonly from lung, ovarian, breast or lymphatic cancer. Ataxia may appear months or years before the cancer is diagnosed.
• Tumor. A growth on the brain, cancerous or noncancerous (benign), can damage the cerebellum.
• Toxic reaction. Ataxia is a potential side effect of certain medications, such as barbiturates, such as phenobarbital, and sedatives, such as benzodiazepines. Alcohol and drug intoxication; heavy metal poisoning — from lead or mercury, for example — and solvent poisoning — from paint thinner, for example — also can cause ataxia.

For some adults who develop sporadic ataxia, no specific acquired or genetic cause can be found. This is known as sporadic degenerative ataxia, which can take a number of forms, including multiple system atrophy (MSA), a progressive, degenerative disorder.

Hereditary ataxias
Some types of ataxia and some conditions that cause ataxia are hereditary. If you have one of these conditions, you were born with a defect in a certain gene that makes abnormal proteins. The abnormal proteins hamper the ability of nerve cells, primarily in your cerebellum and spinal cord, to function properly and cause them to degenerate over time. As the disease progresses, coordination problems worsen.

You can inherit a genetic ataxia from either a dominant gene from one parent (autosomal dominant disorder) or a recessive gene from each parent (autosomal recessive disorder). In the latter case, it's possible neither parent has the disorder (silent mutation), so there may be no obvious family history.

Different gene defects cause different types of ataxia, most of which are progressive. Each type causes poor coordination, but each has specific signs and symptoms.

Autosomal dominant ataxias
These include:

• Spinocerebellar ataxias. Researchers have labeled 28 autosomal dominant ataxia genes with the designation SCA1 through SCA28, generally numbered according to their order of discovery, and the number continues to grow. Cerebellar ataxia and cerebellar degeneration are common to all types, but other signs and symptoms, as well as age of onset, differ depending on the specific gene mutation.
• Episodic ataxia. There are six recognized types of ataxia that are episodic rather than progressive — EA1 through EA6. All but the first two are rare. EA1 involves brief ataxic episodes that may last seconds or minutes; are triggered by stress, being startled or sudden movement; and often are associated with muscle twitching. EA2 involves longer episodes, usually lasting from 30 minutes to six hours, that also are triggered by stress. If you have this type of ataxia, you also may experience dizziness (vertigo), fatigue and muscle weakness during your episodes. In some cases of episodic ataxia, symptoms resolve in later life. Episodic ataxia doesn't shorten life span, and symptoms may respond to medication, such as acetazolamide (Diamox), which also is used to treat seizures, or the anticonvulsant phenytoin (Dilantin).

Autosomal recessive ataxias
These include:

• Friedreich's ataxia. This neurological disorder involves damage to your cerebellum, spinal cord and peripheral nerves. Peripheral nerves carry signals from your brain and spinal cord to your muscles. In most cases, signs and symptoms appear between the ages of 5 and 15, but may occur as early as 18 months or as late as 30 years of age. The rate of disease progression varies. If you have Friedreich's ataxia, however, you're likely to rely on a wheelchair within 15 years of the appearance of symptoms, and your life span may be affected if the disorder includes significant heart disease.

  The first indication generally is difficulty walking (gait ataxia). The condition typically progresses to the arms and trunk. Muscles weaken and waste away over time, causing deformities, particularly in your feet, lower legs and hands. Other signs and symptoms that may develop as the disease progresses include slow, slurred speech (dysarthria); fatigue; rapid, involuntary eye movements (nystagmus); spinal curvature (scoliosis); and heart disease, including heart enlargement (cardiomyopathy) and heart failure.

• Ataxia-telangiectasia. This rare, progressive childhood disease causes degeneration in the brain and other body systems. Signs and symptoms usually appear by age 10. The disease causes immune system breakdown (immunodeficiency disease), which increases susceptibility to other diseases. It affects various organs.

  Telangiectasias are tiny red "spider" veins that may appear in the corners of your child's eyes or on the ears and cheeks. Although they're characteristic of the disease, your child may or may not develop them. Delayed development of motor skills, poor balance and slurred speech are typically the first indications of the disease. Recurrent sinus and respiratory infections are common. About 1 in 5 children with ataxia-telangiectasia develops leukemia or lymphoma because of dysfunction in the immune system. Most people with the disease need a wheelchair by their teens and die in their teens or early 20s.

• Congenital cerebellar ataxia. This type refers to ataxia that results from damage to the cerebellum that's present at birth.
• Wilson's disease. People with this condition accumulate copper in their brains, livers and other organs, which can cause neurological problems, including ataxia.

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