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Coordination disorders 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.
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).
Prolonged, excessive alcohol use permanently damages the cerebellum and is the leading cause 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 Friedrich ataxia, cause loss of coordination. Certain drugs (such as anticonvulsants), especially when they are given in high doses, can cause coordination disorders. In such cases, the disorder may disappear when the drug is stopped.
Causes of Coordination Disorders
People with ataxia cannot 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.
Coordination disorders can cause other abnormalities, such as the following:
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 nystagmus may occur. In nystagmus, the eyes repeatedly move rapidly in one direction, then drift slowly back to their original position.
Tremor: Damage to the cerebellum can also cause a tremor when people end a purposeful movement, such as reaching for an object (intention tremor), or when people try to hold their body in a certain position (postural tremor).
Muscle tone may decrease.
The gene for this disorder 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. Many children with the disorder are born with a clubfoot, curved spine (scoliosis), or both. 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 this disorder 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 these disorders 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. 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 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. SCAs are a common cause of intention tremors (triggered by a purposeful movement). People may have symptoms that resemble those of Parkinson disease (such as tremors and stiff muscles). Sometimes eye movements are impaired, facial muscles and the tongue twitch uncontrollably, and the eyes bulge. Some people have long-lasting (sustained), painful involuntary muscle contractions (dystonia).
The diagnosis is based on symptoms. Doctors also ask about relatives who have had similar symptoms (family history) and about conditions that could cause the symptoms. Magnetic resonance imaging (MRI) of the brain is usually done. Genetic testing is done if people may have a family history of coordination disorders.
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. For hereditary coordination disorders, there is no cure. 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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