What causes ataxia?
The term ataxia describes disease symptoms as well as a group of degenerative diseases of the central nervous system. Types of ataxias include hereditary, acquired and sporadic.
Hereditary ataxias, caused by a gene mutation (change), are inherited from one or both parents. Defective genes make abnormal proteins that cause nerve cells to degenerate and become unable to receive messages from the brain. Symptom development may take years, beginning in childhood or after the patient is an adult. The severity of the disability depends on the type of ataxia and the patient’s age when symptoms first develop.
Hereditary ataxias include:
- Friedreich's ataxia damages the cerebellum, spinal cord and the peripheral nerves that carry messages from the brain and spinal cord to the muscles. Symptoms usually develop before age 25. Muscles weaken and waste away, causing deformities of the feet, lower legs or hands. As the disease progresses, problems develop with speech, hearing, eye movements, fatigue, spinal curvature, and heart disease.
- Ataxia-telangiectasia is a rare childhood disease causing brain degeneration, immune system breakdown, infections, tumors and delayed motor skill development. These children are susceptible to developing cancer and rarely live beyond age 30.
- Congenital cerebellar ataxia results from cerebellum damage that's present at birth.
- Wilson’s disease patients accumulate copper in their brains and other organs. The copper causes neurological problems but an early diagnosis can slow its progression.
- Mitochondrial ataxia is rare. Damage to the cerebellum develops early and causes epilepsy, headache, and speech and eye problems, neuropathy, intellectual disability and movement disorders.
Acquired ataxias usually begin in adulthood, can happen suddenly or develop slowly, and are due to an external cause that happened during the patient’s life. Causes of sudden onset ataxias are varied and include head injuries, stroke, infections, certain cancers and many other causes. These cause damage to the spinal cord or nerves that connect the brain to muscles. Acquired ataxias that develop slowly can be caused by hypothyroidism, alcohol abuse, a vitamin deficiency, chronic exposure to certain drugs, multiple sclerosis and other disorders.
Acquired ataxias include:
- Autoimmune diseases, including multiple sclerosis, sarcoidosis, celiac disease and others.
- Brain abnormalities, such as an abscess (infection), or cancerous or noncancerous growth in the brain, can damage the cerebellum.
- Cerebral palsy, which can damage a child's brain during early development, affects the ability to coordinate movement.
- COVID-19 infection can cause ataxia in severe cases.
- Head trauma, due to a fall or auto accident, can damage the brain or spinal cord.
- Infections, ranging from chickenpox to Lyme disease and HIV, can cause short-term ataxia that usually goes away in several weeks to.
- Paraneoplastic syndromes are rare degenerative disorders, triggered by the immune system's response to a cancerous tumor. They can appear months or years before the cancer is diagnosed.
- Stroke, from either a blockage or bleeding in the brain, causes an interruption of blood to the brain. Brain cells die when deprived of oxygen and nutrients.
- Thyroid problems - either hypothyroidism or hypoparathyroidism - can cause ataxia.
- Toxic reactions to a medication can cause symptoms, especially barbiturates, sedatives, drugs for epilepsy, vitamin B-6 overdose, and some types of chemotherapy. Toxicity can also be caused by alcohol or drug overdose, heavy metal poisoning (lead or mercury), or solvents such as paint thinner.
- Vitamin deficiency, of vitamins E, B-12 or thiamine, can be due to not getting enough vitamins, not being able to absorb vitamins, or from alcohol abuse.
Sporadic ataxia can be very difficult to diagnose. Other types of ataxias must be ruled out before sporadic ataxia can be accurately diagnosed. There is no known cause, and it is not hereditary. It is neurodegenerative, meaning nerve cells in the cerebellum gradually disappear over time. One type of sporadic ataxia affects only the cerebellum. The other type of sporadic ataxia has additional symptoms, including dementia, neuropathy, weakness, rigidity or spasticity of the muscles.
In some patients, sporadic ataxia progresses to multiple system atrophy, which affects the autonomic nervous system that controls blood pressure, digestion, bladder and bowels, and sweating.