Coordination disorders often result from malfunction of the cerebellum, the part of the brain that coordinates voluntary movements and controls balance.
- The cerebellum malfunctions, causing loss of coordination.
- Often, people cannot control their arms and legs, making them take wide, unsteady steps when they walk.
- Doctors base the diagnosis on symptoms, family history, magnetic resonance imaging of the brain, and often genetic testing.
- The cause is corrected if possible, and if it cannot be, treatment focuses on relieving symptoms.
(See also Overview of Movement Disorders.)
The cerebellum is the part of the brain most involved in coordinating sequences of movements. It also controls balance and posture. Anything that damages the cerebellum can lead to loss of coordination (ataxia). However, Many other disorders can also cause loss of coordination.
Causes of Coordination Disorders
The leading cause of coordination disorders is
- Prolonged, excessive alcohol use, which permanently damages the cerebellum
Stroke and multiple sclerosis are also common causes of coordination disorders.
Less commonly, other disorders, such as an underactive thyroid gland (hypothyroidism), vitamin E deficiency, and brain tumors, cause coordination disorders. Some hereditary disorders, such as Friedreich ataxia, cause loss of coordination.
Rarely, in people with cancer (especially lung cancer), the immune system malfunctions and attacks the cerebellum—an autoimmune reaction. This disorder, called subacute cerebellar degeneration, results in loss of coordination.
Certain drugs (such as antiseizure drugs), especially when they are given in high doses, can cause coordination disorders. In such cases, the disorder may disappear when the drug is stopped.
Did You Know...
Causes of Coordination Disorders
Disorders that affect the structure of the cerebellum
Birth defects of the cerebellum
Bleeding (hemorrhage) in the cerebellum
Tumors in the cerebellum, particularly in children
Head injuries (repeated)
Strokes that affect the cerebellum
Subacute cerebellar degeneration
Heatstroke or extremely high fever
Drugs and toxic substances
Alcohol use (excessive and prolonged)
Antiseizure drugs such as phenytoin, particularly at high doses and taken for a long time
Heavy metals such as mercury or lead
Sedatives (such as benzodiazepines) at high doses
Symptoms of Coordination Disorders
Loss of coordination prevents people from being able to control the position of their arms and legs or their posture. Thus, when they walk, they take wide steps and stagger and make broad, zigzag movements with their arms when they reach for an object.
Coordination disorders can cause other abnormalities, such as the following:
- Ataxia: Coordination is lost. People may be unsteady when they walk and take wide steps. They may need to hold onto furniture and walls to move about.
- Dysmetria: People cannot control the range of body movements. For example, in attempting to reach for an object, people with dysmetria may reach beyond the object.
- Dysarthria: Speech is slurred, and fluctuations in volume cannot be controlled because speech muscles are uncoordinated. Movement of the muscles around the mouth may be exaggerated.
- Scanning speech: People speak in a monotone with a tendency to hesitate at the beginning of a word or syllable.
- Nystagmus: When glancing at an object, the eyes may overshoot their target, and/or nystagmus may occur. In nystagmus, the eyes repeatedly move rapidly in one direction, then return a little more slowly to their original position.
- Tremor: Damage to the cerebellum can also cause a tremor when people attempt a purposeful movement, such as reaching for an object (intention tremor), or when people try to hold a limb outstretched in one position (postural tremor).
Muscle tone may decrease.
Friedreich ataxia is a hereditary disorder. The gene for Friedreich ataxia is recessive. Thus, to develop the disorder, people must inherit two copies of the abnormal gene, one from each parent.
Friedreich ataxia is progressive. Walking becomes unsteady between the ages of 5 and 15. Then arm movements become uncoordinated, and speech becomes slurred and hard to understand.
People with Friedreich ataxia cannot sense vibrations, cannot sense where their arms and legs are (lose their position sense), and no longer have reflexes. Mental function may deteriorate. Tremor, if present, is slight.
Heart problems often develop and become progressively worse.
By their late 20s, people with Friedreich ataxia may be confined to a wheelchair. Death, often due to an abnormal heart rhythm or heart failure, usually occurs by middle age.
The gene for spinocerebellar ataxias (SCAs) is dominant. Thus, having only one copy of the abnormal gene, inherited from one parent, is sufficient to cause the disorder. There are many different types of these ataxias. Worldwide, SCA type 3 (formerly called Machado-Joseph disease) may be the most common. These disorders are progressive, degenerative, and often eventually fatal. There is no known effective treatment.
Symptoms of SCAs vary by type, but most cause problems with sensation (for example, people feel pain, touch, and vibration less well or not at all), muscle weakness, and restless legs syndrome, as well as loss of coordination. People have problems with balance, speech, and eye movements. Some types typically cause only loss of coordination.
SCAs are a common cause of intention tremors (triggered by a purposeful movement). People may have symptoms that resemble those of Parkinson disease (parkinsonism), such as tremors and stiff muscles.
Some people with SCA type 3 have other symptoms in addition to loss of coordination and tremors. Their eye movements may be impaired, their facial muscles and the tongue may twitch uncontrollably, and their eyes may bulge. Some people have long-lasting (sustained), painful involuntary muscle contractions (dystonia).
Diagnosis of Coordination Disorders
- A doctor's evaluation
- Usually magnetic resonance imaging
- Genetic testing
The diagnosis of coordination disorders is based on symptoms. Doctors also ask about relatives who have had similar symptoms or conditions that could cause the symptoms. (family history). Doctors also do a physical examination, including a neurologic examination, to check for conditions that could cause the symptoms in the affected person.
Magnetic resonance imaging (MRI) of the brain is usually done.
Genetic testing is being increasingly done in people who may have a family history of coordination disorders.
Treatment of Coordination Disorders
- Treatment of the cause if possible
- Physical and occupational therapy
If possible, the cause is eliminated or treated. For example, if the coordination disorder is due to use of alcohol, alcohol is stopped. If the disorder is caused by a high dose of a drug (such as phenytoin), the dose is reduced. Some underlying disorders, such as hypothyroidism and vitamin E deficiency, can be treated. Surgery may help some people with brain tumors.
There is no cure for hereditary coordination disorders. In such cases, treatment focuses on relieving symptoms.
Physical therapists can teach people specific exercises that may help improve balance, posture, and coordination. These exercises can help people walk more normally and function more independently. Occupational therapists may also recommend devices that can help with walking, eating, and other daily activities. Speech therapy may also help.
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