Ataxia is derived from the Greek word meaning "irregularity" or "disorderliness" but when used medically, the term describes a condition characterized by poor motor coordination. Ataxia causes incoordination of hands, staggering gait, and slurred speech, which may make the person appear "drunk." Ataxic patients are unable to walk in a straight line and tend to bump into things. In advanced stages they may need a walker or even a wheelchair. Patients also may have blurring of vision due to eye movement abnormalities. In addition to these motor incoordination due to problems with the cerebellum (the posterior portion of the brain responsible for coordination), ataxia can also occur as a result of problems with disturbance of the sensory system (abnormal perception of a position of a body part in space) and vestibular system (abnormal balance). A neurologist can usually differentiate between the two types of ataxia: motor and sensory.
There are about 150,000 patients affected with some form of ataxia in the United States. There are many causes of ataxia but most can be categorized as sporadic (no specific cause), genetic or secondary to some injury to the brain. Congenital ataxias occur in children, and they are due to structural abnormalities in the brain that occur before or during birth. These include cerebral palsy (often associated with injury to the brain at birth due to lack of oxygen or blood supply), hydrocephalus (increased pressure caused by blockage or build up of cerebrospinal fluid) or brain tumors, and other injuries to the brain.
Ataxia can be acute (sudden), subacute (within a week) or chronic (slowly progressing over years). In acute cases the most common cause is either stroke or hemorrhage in the area of the cerebellum. Patients usually have headache, vomiting, neck stiffness or loss of consciousness. In children, bacterial or viral infections can cause acute ataxia and this usually improves with time. Patients develop fever, problems with walking and slurred speech over a period of hours to days and recover in a few weeks. MRI and spinal fluid analysis are helpful in diagnosis. Subacute onset of ataxia is usually seen in paraneoplastic cerebellar degeneration. This is a condition in which cancer in the breast, lungs, ovaries or other areas in the body can cause ataxia.
Episodic ataxia is a disorder with intermittent spells of ataxia with complete recovery between episodes. The best characterized are types 1 and 2. These are dominantly inherited cerebellar ataxias. They are caused by genetic mutations within a voltage gated potassium channel (KCNA1) gene and the cerebral P/Q type calcium channel gene (CACNL1A4) respectively. Patients have spells of gait difficulty, dysarthria and nystagmus with complete recovery between episodes. Genetic episodic ataxias are responsive to medical treatment. Drug ingestion, multiple sclerosis and other causes can also lead to episodic ataxia in some cases.
Patients with chronic progressive ataxia have long standing difficulties over several years. These include several disorders like degeneration of cerebellum due to alcohol, hereditary cerebellar ataxias, brain tumors in children, vitamin E or copper deficiency. Vitamin B12 deficiency causes sensory ataxia in addition to muscle weakness.
Spinocerebellar ataxias (SCA) represent the most common form of chronic progressive ataxia in adults. They result from degeneration of pathways between the spinal cord and cerebellum. There are many types (SCA 1 to 30 see table for reference) and the number is increasing based on new research. Most of these disorders are genetic and have a 50 percent chance of transmission to children (autosomal dominant pattern of inheritance). All patients with these disorders must undergo genetic counseling.
SCA-2 is most common in the US and SCA3 is most common in Japan, Germany, Portugal and France. Typical age of onset of these syndromes is 4-60 years with average of 40 years. Although the type of SCA varies patients can become disabled by five years, bedridden by ten years and death occurs any where between 10-20 years after onset of disease.
The common clinical problems in SCA are gait ataxia, eye movement abnormalities (nystagmus or jerkiness and double vision), and dysarthria (speech difficulty). Some of the SCAs (SCA1,2,3,4,7 and 8) also cause peripheral neuropathy (damage to the peripheral nerves which causes the patient to have numbness or tingling in the hands and feet). Some SCA can result in blindness by causing damage to the retina and the macula in the eye (SCA 7).
In addition to SCAs there are other inherited disorders that can cause ataxia, including DRPLA (dentatorubro-pallidoluysian atrophy). This is a rare neurodegenerative disorder that causes difficulties with walking (ataxia), problems with speech, dementia, chorea (involuntary writhing type of movements) and jerkiness of muscles (myoclonus). Some of the younger patients have seizures.
Besides autosomal dominant forms of ataxia, there are also autosomal recessive ataxias, in which each offspring has 25 percent, rather than 50 percent, risk of inheritance from the parents when both parents are carriers of the gene mutation (that means they carry the gene but do not have the symptoms of the disease). Friedrich's ataxia is an example of autosomal recessive ataxia. It is a disorder due to excessive repeats of nucleotides GAA in the DNA. Patients have ataxia along with spasticity, speech problems, nystagmus, weakness of lower extremities, and sensory problems. Patients with Friedreich's ataxia also may develop scoliosis (curvature of spine), cardiomyopathy (enlargement of the heart), and diabetes and bowel and bladder dysfunction. This is a slow progressive disorder but most patients become wheelchair bound within 10-20 years after onset. There is, however, a marked variability in the presentation and progress of the disease. Other recessively inherited ataxias include vitamin-E deficiency (due to alpha tocopherol transfer protein deficiency or abetalipoproteinemia), ataxia telangiectasia, ataxia with oculomotor apraxia type I and II, and infantile onset spinocerebellar ataxia among several others.
Ataxia can be a part of Fragile X-associated tremor / ataxia syndrome (FXTAS). This is a genetic disorder with a gene located on X-chromosome (female sex chromosome). It affects mainly male but can occur in female carrier of the mutation. The clinical spectrum of FXTAS includes progressive ataxia, tremor, cognitive decline and sometimes other features.
Of all the movement disorders ataxia is among the most resistant to medical therapy. Clonazepam may help tremor and balance problems. It has side effects such as sedation, fatigue loss of libido etc. Other medications such as buspirone or 5-hydroxytryptophan have been studied but they have not been shown to be very beneficial. Phenytoin, an anticonvulsant, is useful for some episodic ataxias. Acetazolamide is useful in some of the rare forms of episodic ataxias such as episodic ataxia with paroxysmal choreoathetosis and spasticity (episodes of ataxia with stiffness and writhing type of abnormal movements).
Cerebellar ataxias including the genetic ataxias however do not have any definitive treatments. Some of the disorders have been reported to be slowed by taking antioxidants such as vitamins A, E, B12, idebenone, and Coenzyme Q10. Vitamin E is the treatment of choice in ataxia caused by vitamin E deficiency. Vitamin B12 or copper supplements are used to treat ataxia related to vitamin B12 or copper deficiency respectively. When associated with parkinsonism, such as seen in the cerebellar form of multiple system atrophy (previous referred to as olivopontocerebellar atrophy), levodopa may be helpful.
Weakness and spasticity contribute to the difficulties the patient may experience in ataxia. Physical therapy to maximize strength, conditioning and flexibility are helpful. General physical therapy and regular exercise are highly recommended. Early therapy may help patients with spasticity from developing contractures. Patients with ataxia can be helped with gait training during the earlier stages of the disease. Adaptations such as wheel chair and home adjustments can be discussed with the occupational therapist. Speech therapy can be helpful for patients with dysarthria.
Care of the bed-ridden patient in advanced stages of the progressive ataxia is very important. Skin care and eventual placement of PEG tube (feeding tube) in patients with swallowing difficulties will help prevent lung infections.
For more information, see Appendix - Classification of Spinocerebellar Ataxias.
There are many ataxias that are yet to be classified and further research into treatment and cause of these disorders is awaited. The following organizations can provide further information for specific disorders:
©2011 Joseph Jankovic, M.D.
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