Causes

Damage, degeneration or loss of nerve cells in the part of your brain that controls muscle coordination (cerebellum), results in ataxia. Your cerebellum comprises two portions of folded tissue situated at the base of your brain near your brainstem. This area of the brain helps with balance as well as eye movements, swallowing and speech.

Diseases that damage the spinal cord and peripheral nerves that connect your cerebellum to your muscles also can 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 acute cerebellar ataxia, which comes on suddenly.
• Stroke. Either a blockage or bleeding in the brain can cause ataxia. When the blood supply to a part of your brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients, brain cells die.
• 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.
• Autoimmune diseases. Multiple sclerosis, sarcoidosis, celiac disease and other autoimmune conditions can cause ataxia.
• Infections. Ataxia can be an uncommon complication of chickenpox and other viral infections such as HIV and Lyme disease. It might appear in the healing stages of the infection and last for days or weeks. Normally, the ataxia resolves 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 can appear months or years before the cancer is diagnosed.
• Abnormalities in the brain. An infected area (abscess) in the brain may cause ataxia. A growth on the brain, cancerous (malignant) or noncancerous (benign), can damage the cerebellum.

• Toxic reaction. Ataxia is a potential side effect of certain medications, especially barbiturates, such as phenobarbital; sedatives, such as benzodiazepines; antiepileptic drugs, such as phenytoin; and some types of chemotherapy. Vitamin B-6 toxicity also may cause ataxia. These causes are important to identify because the effects are often reversible.

  Also, some medications you take can cause problems as you age, so you might need to reduce your dose or discontinue the medication.

  Alcohol and drug intoxication; heavy metal poisoning, such as from lead or mercury; and solvent poisoning, such as from paint thinner, also can cause ataxia.

• Vitamin E, vitamin B-12 or thiamine deficiency. Not getting enough of these nutrients, because of the inability to absorb enough, alcohol misuse or other reasons, can lead to ataxia.
• Thyroid problems. Hypothyroidism and hypoparathyroidism can cause ataxia.
• COVID-19 infection. This infection may cause ataxia, most commonly in very severe cases.

For some adults who develop sporadic ataxia, no specific cause can be found. Sporadic ataxia can take a number of forms, including multiple system atrophy, 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 function of nerve cells, primarily in your cerebellum and spinal cord, and cause them to degenerate. 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 might 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 identified more than 40 autosomal dominant ataxia genes, 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 (EA). There are eight recognized types of ataxia that are episodic rather than progressive — EA1 through EA7, plus late-onset episodic ataxia. EA1 and EA2 are the most common. EA1 involves brief ataxic episodes that may last seconds or minutes. The episodes 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, which also are triggered by stress. You might have dizziness (vertigo), fatigue and muscle weakness during your episodes. In some cases, symptoms resolve in later life.

  Episodic ataxia doesn't shorten life span, and symptoms might respond to medication.

Autosomal recessive ataxias

These include:

• Friedreich's ataxia. This common hereditary ataxia 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 well before age 25.

  The rate of disease progression varies. 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 might develop as the disease progresses include slow, slurred speech (dysarthria); fatigue; rapid, involuntary eye movements (nystagmus); spinal curvature (scoliosis); hearing loss; and heart disease, including heart enlargement (cardiomyopathy) and heart failure. Early treatment of heart problems can improve quality of life and survival.

• Ataxia-telangiectasia. This rare, progressive childhood disease causes degeneration in the brain and other body systems. The disease also causes immune system breakdown (immunodeficiency disease), which increases susceptibility to other diseases, including infections and tumors. It affects various organs.

  Telangiectasia is the formation of tiny red "spider" veins that might appear in the corners of your child's eyes or on the ears and cheeks. Delayed motor skill development, poor balance and slurred speech are typically the first indications of the disease. Recurrent sinus and respiratory infections are common.

  Children with ataxia-telangiectasia are at high risk of developing cancer, particularly leukemia or lymphoma. Most people with the disease need a wheelchair by their teens and die before age 30, usually of cancer or lung (pulmonary) disease.

• Congenital cerebellar ataxia. This type of ataxia 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. Early identification of this disorder can lead to treatment that will slow progression.