The word "ataxia" means lack of coordination. People with ataxia have problems with balance and coordination when performing voluntary movements. The word “ataxia” does not indicate a specific disease. Rather, ataxia is a symptom that can result from a number of different diseases. These diseases affect the parts of the central nervous system that normally control balance and coordination.
Ataxia can affect people in many different ways. Depending on the underlying disease, patients might manifest some symptoms but not others. The age of onset as well as the severity of the symptoms vary among individuals.
Many conditions might cause ataxia. Ataxia occurs when the underlying pathologic process affects the parts of the brain that control balance and coordination, such as the cerebellum, a large structure located in the back of the head.
1. Hereditary or Genetic Forms of Ataxia
These forms occur when abnormal genes are passed on in families. The most common forms of hereditary ataxias are the spinocerebellar ataxias (SCAs) and Friedreich’s ataxia.
SCAs are inherited in an autosomal dominant fashion. This means that each child of a parent with SCA has a 50% chance of being affected as well, and a 50% chance of being ataxia-free. There are 26 types of SCAs, and the number keeps growing based on new research. SCAs typically present in adulthood. Each subtype of SCA is characterized by a different set of symptoms that may be difficult to differentiate on the basis of clinical examination alone. Therefore, the only definitive way to identify what type of SCA affects a particular patient is through genetic testing.
Friedreich’s ataxia is the most common form of recessively inherited ataxia and generally presents during childhood. In order for a child to be affected, both parents must be carriers of the disease gene. Carriers do not have symptoms but the offspring of two carriers has a 25% chance of developing the disease. Children of two carriers have a 50% chance of being carriers themselves and a 25% of not inheriting the ataxia gene.
Gene testing is available for many forms of hereditary ataxia, including some SCAs and Friedreich’s ataxia. When a hereditary form of ataxia is suspected, genetic testing may lead to precisely diagnosing a specific ataxia subtype. However, not all the genes that cause ataxia are known. As a consequence, some patients with a positive family history of ataxia may result negative when tested for the genetic mutations that are currently known to be associated with hereditary ataxia. Gene testing may also be used to identify asymptomatic individuals who are at risk of developing ataxia. Genetic counselors can help patients and their families make an informed decision about gene testing.
2. Sporadic (Degenerative) Ataxia
People with sporadic (degenerative) ataxia have no family history of this disease. Diagnosis in such cases may be challenging, as no specific test is available. These forms of ataxia result from degeneration of the cerebral pathways that regulate balance and coordination. Patients generally manifest symptoms of ataxia in adulthood and may present with additional symptoms such as Parkinsonian features (stiffness, slow movements, tremor at rest) or autonomic neuropathy (difficulty controlling blood pressure and bladder and bowel function).
3. Secondary Ataxia
Ataxia can be secondary to many medical and neurological conditions, and can either appear suddenly or gradually. Examples of conditions that may produce ataxia are:
Because ataxia can be brought about by many different diseases, it is important that patients undergo a thorough diagnostic evaluation, planned by an experienced neurologist, in order to rule out treatable conditions and to institute an appropriate treatment and management plan.
Diagnostic tests generally include:
During the clinical evaluation, a physician who specializes in ataxia might detect clues, such as symptoms and physical findings, suggestive of a particular form of ataxia. The physician would plan the subsequent diagnostic work-up accordingly.
Brain imaging studies, such as Magnetic Resonance Imaging (MRI), are very useful to look for brain abnormalities, e.g. “shrinkage” or atrophy of the cerebellum, that are common to some forms of ataxia. MRI can also help to rule out other causes of ataxia, such as stroke, tumors multiple sclerosis, and congenital malformations.
Blood tests are important to uncover such causes of ataxia as vitamin deficiencies, metabolic problems like hypothyroidism, and infectious diseases, e.g. HIV and syphilis.
Depending on the individual presentation, additional tests might be recommended. These include:
1 Evoked potentials, to measure electrical activity of the brain in response to stimulation of specific sensory nerve pathways
2 Vestibular function tests and posturography to investigate balance problems
3 Electroencephalography (EEG), to detect abnormalities in electrical brain activity.
Treatment of ataxia depends on underlying cause. When ataxia is secondary to a medical or neurological disease, a specific treatment can be instituted to address that particular problem, e.g. vitamin E or vitamin B 12 deficiencies.
On the other hand, when ataxia is due to genetic or unknown causes, no definitive cure is available. Clinical research is currently underway to test different compounds, e.g. vitamin E and Co-enzyme Q-10, which are potentially useful in slowing the disease course. In addition, some drugs are being tested for use in rare forms of genetic ataxias: zolpidem in SCA2; acetazolamide and phynytoin in some types of episodic ataxia.
The quality of life of patients with ataxia can be significantly improved by adhering to a multidisciplinary management plan that is aimed at maximizing individual skills and overcoming barriers and limitations. Patients are encouraged to work with a physical therapist for gait training and to improve strength and flexibility. A speech language pathologist can help patients to improve communication problems. Occupational therapists can help the individual to retain as much independence as possible by suggesting home adjustments and strategies for self-care, feeding, and writing. Devices such as can, walker, or wheelchair may also be useful, depending on symptom severity. Social workers can counsel patients and families re: coping skills, available community resources, problem-solving, and emotional support.
Lastly, medications are available to relive symptoms that are sometimes associated with ataxia, e.g. tremor, stiffness, spasticity, and balance problems.