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 Overview of Movement Disorders Every body movement, from raising a hand to smiling, involves a complex interaction between the central nervous system (brain and spinal cord), nerves, and muscles. Damage to or malfunction... read more .)
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 Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more 
), vitamin E deficiency Vitamin E Deficiency Vitamin E deficiency caused by a diet low in vitamin E is common in countries with high rates of food insecurity. In countries with low rates of food insecurity, the cause is usually an absorption... read more , and brain tumors Overview of Brain Tumors A brain tumor can be a noncancerous (benign) or cancerous (malignant) growth in the brain. It may originate in the brain or have spread (metastasized) to the brain from another part of the body... read more , cause coordination disorders. Some hereditary disorders, such as Friedreich ataxia Friedreich ataxia 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... read more , 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 Neurologic syndromes , results in loss of coordination.
Certain drugs (such as antiseizure drugs Antiseizure drugs In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more ), especially when they are given in high doses, can cause coordination disorders. In such cases, the disorder may disappear when the drug is stopped.
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 Dysarthria Dysarthria is loss of the ability to articulate words normally. Speech may be jerky, staccato, breathy, irregular, imprecise, or monotonous, but people can understand language and use it correctly... read more : 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 Tremor A tremor is an involuntary, rhythmic, shaking movement of part of the body, such as the hands, head, vocal cords, trunk, or legs. Tremors occur when muscles repeatedly contract and relax. (See... read more : 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
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.
Many children with the disorder are born with a clubfoot Clubfoot and Other Foot Defects Clubfoot (talipes equinovarus) is a birth defect in which the foot and ankle are twisted out of shape or position. Birth defects, also called congenital anomalies, are physical abnormalities... read more 
, curved spine (scoliosis Scoliosis Scoliosis is abnormal curvature of the spine. Scoliosis can be present at birth or can develop during adolescence. Mild forms may cause only mild discomfort, but more severe forms can cause... read more 
), 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 Friedreich ataxia may be confined to a wheelchair. Death, often due to an abnormal heart rhythm or heart failure, usually occurs by middle age.
Spinocerebellar ataxias
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 Periodic Limb Movement Disorder (PLMD) and Restless Legs Syndrome (RLS) Periodic limb movement disorder involves repetitive movements of the arms, legs, or both during sleep. Restless legs syndrome involves an irresistible urge to move and usually abnormal sensations... read more , 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 Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more ), 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 Dystonia Dystonia is characterized by long-lasting (sustained) involuntary muscle contractions that may force people into abnormal positions—for example, causing the entire body, the trunk, limbs, or... read more ).
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 Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the different parts of the nervous system. Examination... read more , to check for conditions that could cause the symptoms in the affected person.
Magnetic resonance imaging Magnetic Resonance Imaging (MRI) Magnetic resonance imaging (MRI) is a type of medical imaging that uses a strong magnetic field and very high frequency radio waves to produce highly detailed images. During an MRI, a computer... read more 
(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. Riluzole may help improve coordination in the short-term.
Physical therapists Physical Therapy (PT) Physical therapy, a component of rehabilitation, involves exercising and manipulating the body with an emphasis on the back, upper arms, and legs. It can improve joint and muscle function, helping... read more 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 Occupational Therapy (OT) Occupational therapy, a component of rehabilitation, is intended to enhance a person's ability to do basic self-care activities, useful work, and leisure activities. These activities include... read more may also recommend devices that can help with walking, eating, and other daily activities. Speech therapy Rehabilitation for Speech Disorders Rehabilitation services are needed by people who have lost the ability to speak normally, often because of an injury, a stroke, an infection, a tumor, surgery, or a progressive disorder. Aphasia... read more may also help.
