sections include: the many possible causes, diagnosis and treatment
The word ataxia is derived from Greek roots that mean “without order.” In a medical sense, it refers to lack of coordination. The first sign of the condition is usually walking with poor balance and a slow and unsteady gait. That is often followed by impaired hand coordination, including deteriorating handwriting and difficulty with complex hand motions. Later a person may have slurred and inarticulate speech. Ataxia can also be associated with shaking or tremors, especially when a person tries to use his or her hands. It occasionally shows up as altered eye movements, producing distorted vision and impaired perception of movement.
To outsiders, a person suffering from ataxia may seem drunk: reeling unsteadily, slurring his or her speech, and making uncoordinated hand gestures. But people with the condition, their family, and their friends know that alcohol is not the cause. Usually the person’s obvious difficulty in walking causes the family to seek medical attention quickly. They are often concerned that the symptoms are due to a stroke, brain tumor, multiple sclerosis, or other serious neurological disorders, and indeed ataxia might be the first sign of those problems. Diagnosing ataxia and its cause as rapidly as possible is important to prevent further losses of coordination and to obtain the best chance for full recovery.
Ataxia can indicate a serious medical emergency, especially when the problem is associated with any of these additional symptoms:
- nausea or vomiting
- decreased alertness
- impaired coordination on only one side of the body
It is therefore important to note how the problem begins and how quickly it grows. If the ataxia is one-sided and develops suddenly, it may be due to a large stroke or hemorrhage affecting the part of the brain that controls coordination and balance. The presence of other serious symptoms—headache, nausea, vomiting, and decreased alertness—might indicate that an abscess or tumor is putting pressure on that part of the brain. This increased pressure may also compress the brain stem underneath, causing more neurological symptoms: altered breathing; dizziness and paralysis of muscles in the face, arm, or leg; impaired swallowing; and impaired comprehension of language and speech. Once again, a person should see a neurologist as quickly as possible when ataxia appears.
The Many Possible Causes
Like hearing loss or dizziness, ataxia is a symptom that can be produced by many conditions. Something is interfering with the brain’s elaborate system to regulate and coordinate the movement of muscles. The main component of this motor regulatory system is the cerebellum, located in the back of the brain near the junction of the head and neck. The cerebellum lies over the brain stem and is neuroanatomically connected to it. When the brain issues a command to move a set of muscles for a specific activity, the brain’s motor neurons send electrical messages through the brain stem to the spinal cord motor neurons, which in turn activate the appropriate set of muscles. At the same time, electrical messages go to the cerebellum, telling it exactly in what direction, how fast, and how forceful the intended motor activity should be. The job of the cerebellum is to modulate the motor neurons so that the motion occurs in the precise direction, at the correct speed, and with the proscribed amount of force. If the cerebellum or its connections to the brain stem are impaired, it can’t send these corrective electrical signals. That results in the poorly coordinated motor functions that define ataxia.
Ataxia is a rather common neurological condition, occurring most often after a stroke or hemorrhage in the brain. As noted above, ataxia on only one side of the body is frequently the first sign of these underlying conditions. The treatment for stroke and hemorrhages is discussed in detail here and here.
Here we will emphasize the best ways to prevent these problems, and thus to prevent this form of ataxia. People with high blood pressure, elevated serum cholesterol and lipids, or diabetes mellitus are at particular risk for stroke or brain hemorrhage. Individuals with these medical conditions therefore need to seek medical attention as soon as possible to correct them. People over 60 years old are also more at risk for these disorders and should have a medical evaluation at least once a year.
There are several other possible causes of ataxia as well, especially when it’s not accompanied by the additional symptoms listed above. In determining the cause of the problem, a physician will have to consider all of these:
- A tumor, abscess, or other growth within the brain.
- Medication that reaches a toxic level in the blood. The drugs that most commonly cause problems include lithium, diphenylhydantoin (Dilantin for epilepsy), and barbiturates.
- Exposure to mercury, solvents, gasoline, and glue, among other poisons. Doctors will test for traces of these substances if the person’s history indicates they might be the cause.
- A recent infection, such as pneumonia.
- Deficiencies of specific vitamins, such as B1 and B12.
- Hypothyroidism—an underactive thyroid gland.
- The human immunodeficiency virus (HIV). AIDS-related disorders can result in a severe form of ataxia, and a test for HIV is necessary.
- Tumors outside the brain that have caused the body to form antibodies that react with the cerebellar tissue in the brain, producing a paraneoplastic syndrome with ataxia. If a person is at high risk for a systemic cancer— for instance, a tocacco smoker facing the increased likelihood of lung cancer—doctors will look into this possibility carefully.
Finally, ataxia may also be due to a genetic disorder. If one person in a family develops ataxia without a clear cause from the list above, then a child or sibling of that person should seek genetic counseling and have a neurological examination. A careful family history should be obtained to determine if an inheritance pattern can be found. This pattern will be important to decide the percent of risk to develop ataxia for a child of an affected parent.
Diagnosis and Treatment
Diagnosing the problem underlying ataxia starts with taking a careful history of the onset and development of the symptom, and doing a detailed neurological examination to determine the pattern of the neurological abnormalities. Measuring a person’s blood pressure and heart function is useful, as are blood tests for drugs, vitamin levels, thyroid function, toxins and metals, HIV and other infections, and paraneoplastic antibodies when a person’s history suggests any of these might be the cause of the problem. A brain scan is often helpful for spotting growths or other problems within the skull. If the ataxia suggests the problem may be multiple sclerosis or infection, a spinal tap to obtain cerebrospinal fluid may be necessary.
The history of the condition, the neurological examination, and the laboratory tests combine with a high level of accuracy to determine the cause of the ataxia. Strokes, hemorrhages, or tumors are quickly identified. Tests for toxic substances, infections, and systemic cancers help zero in on these potential causes or rule them out. Genetic tests, especially the new DNA tests, are also highly specific; because neurologists are trained to diagnose the cause of ataxia in general, however, consulting a neurogeneticist may be necessary for the rarer genetic diseases.
Treatments will, of course, depend on the cause of the ataxia and the amount of damage a person has already suffered. Doctors will pay careful attention to the person’s airway, and if increasing brain pressure starts to affect his or her natural respiration, a breathing tube and respirator may need to be used for a short time. Large lesions inside the cerebellum may be harming the brain stem, requiring urgent surgery to relieve this pressure. Antibiotics are required if there is a bacterial or fungal infection in the cerebellum and the membranes lining the brain, causing meningitis. High-dose steroids are indicated if the cause is acute multiple sclerosis.
Sometimes the ataxia is the result of a series of problems, all of which need to be treated. If a stroke or hemorrhage has occurred in the person’s cerebellum, doctors will focus on correcting any remaining high blood pressure; this is essential and can be life-saving. Such a stroke may have been caused by a blood clot traveling from the heart to the brain; in this case, carefully thinning the blood with anticoagulants may be necessary to prevent further clots from developing. And such a blood clot may have been the result of an underlying heart attack, which itself demands intensive care.
Ataxia can be a mild neurological condition, or it can rapidly develop into a serious problem. Recovery depends on how much the brain tissue has been compromised and how rapidly the condition is corrected, either spontaneously or due to therapy. Most people with ataxia arising from common causes, such as stroke, recover nicely. Long-term improvement is common and helped along by careful medical reevaluations and physical rehabilitation. Some ataxias with less common origins do not allow as good a chance at recovery. Many excellent laboratories are studying how to regenerate brain tissue using stem cells, which could be one way to counteract the problem. Other researchers are seeking ways to correct or compensate for the genetic mutation that can cause ataxia.
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