PhytoScience - Article

Ataxia


Ataxia describes a lack of muscle coordination when you perform voluntary movements, such as walking or picking up objects. It's a sign of an underlying condition, not a disease itself. Ataxia can affect any part of your body; affecting your movements, your speech, your eye movements and your ability to swallow. Drinking too much alcohol may cause temporary ataxia, affecting your speech, hand-eye coordination and ability to walk.

Persistent ataxia is usually the result of damage to the part of your brain that controls muscle coordination (cerebellum). Many conditions may cause ataxia, including stroke, tumor, cerebral palsy and multiple sclerosis. You may also inherit a defective gene that may cause one of many variants of ataxia.

Treatment for ataxia depends on the underlying cause. Adaptive devices, such as walkers or canes, might help you maintain your independence despite your ataxia. You may also benefit from physical therapy, occupational therapy and speech therapy.

Signs and symptoms

The part of your brain that controls muscle coordination, your cerebellum, comprises two ping- pong-ball-sized portions of folded tissue situated at the base of your brain, near your brainstem. The right side of your cerebellum controls coordination on the right side of your body; the left side of the cerebellum controls coordination on the left side of your body.

Ataxia usually is a result of damage to your cerebellum from disease, infection or injury. It can develop over time or come on suddenly, depending on the cause. Signs and symptoms of ataxia include:

  • Unsteady walk
  • Tendency to stumble
  • Slurred speech
  • Difficulty with fine-motor tasks, such as eating or buttoning a shirt
  • Slow eye movements
  • Difficulty swallowing

Causes

The most common cause of ataxia is damage to your cerebellum, which may be the result of any number of conditions. Diseases that damage the spinal cord and peripheral nerves that connect your cerebellum to your muscles may also cause ataxia. Ataxia causes include:

  • Head trauma. Damage to your brain or spinal cord from a blow to your head, such as might occur in a car accident, can cause sudden onset ataxia, also known as acute cerebellar ataxia.

  • Stroke. When the blood supply to a part of your brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients, brain cells begin to die.

  • Transient ischemic attack (TIA). Caused by a temporary decrease in blood supply to part of your brain, most TIAs last only a few minutes. Loss of coordination and other signs and symptoms of a TIA are temporary.

  • Cerebral palsy. This is a general term for a group of disorders caused by damage to a child's brain during early development {before, during or shortly after birth} that affects the child's ability to coordinate body movements.

  • Multiple sclerosis (MS). MS is a chronic, potentially debilitating disease that affects your central nervous system, which comprises your brain and spinal cord.

  • Chickenpox. Ataxia can be an uncommon complication of chickenpox and other viral infections. It may appear in the healing stages of the infection and last for days or weeks. Normally, the ataxia resolves completely over time.

  • Paraneoplastic syndromes. These are rare, degenerative disorders triggered by your immune system's response to a cancerous tumor (neoplasm), most commonly from lung, ovarian, breast or lymphatic cancer. Ataxia may appear months or years before the cancer is diagnosed.

  • Tumor. A growth on the brain, cancerous or noncancerous (benign), can damage the cerebellum.

  • Toxic reaction. Ataxia is a potential side effect of certain medications, such as phenobarbital and sedatives such as benzodiazepines. Alcohol and drug intoxication; heavy metal poisoning, such as with lead or mercury; and solvent poisoning, such as with paint thinner, also can cause ataxia.

Hereditary ataxias
Some types of ataxia and some other conditions that cause ataxia are hereditary. If you have one of these conditions, you were born with a defect in a certain gene that makes abnormal proteins. The abnormal proteins hamper the ability of nerve cells, primarily in your cerebellum and spinal cord, to function properly and cause them to degenerate over time. As the disease progresses, coordination problems worsen.

You can inherit a genetic ataxia in different ways. Genes occur in pairs; you receive half of each pair from your mother, half from your father. Genes are either dominant or recessive, with the effects of a dominant gene in a pair taking precedence over the effects of the recessive gene.

If the dominant gene carries a defect, that mutation will control the gene's expression, sometimes resulting in disease. Diseases that are caused by dominant gene mutations are called autosomal dominant disorders.

Some mutations that cause ataxias occur in recessive genes. Diseases that are caused by recessive gene mutations are called autosomal recessive disorders. For you to inherit such a disorder, both of your parents must carry the associated recessive genetic mutation, even if they don't have the disorder themselves (silent mutation). In this case, they are only "carriers" of the disorder, so there may be no apparent family history of the disorder.

Different gene defects cause different types of ataxia, most of which are progressive. Each type causes poor coordination, but each has specific signs and symptoms by which they can be identified. Ataxia may result from either an autosomal recessive disorder or an autosomal dominant disorder.

Autosomal recessive ataxias
These include:

  • Friedreich's ataxia. This neurological disorder involves damage to your cerebellum, spinal cord and peripheral nerves. Peripheral nerves carry signals from your brain and spinal cord to your muscles. It was once believed to be a childhood disease, with onset occurring before age 25. However, with the identification of the gene defect that causes the disease, experts now recognize that there is an adult-onset Friedreich's ataxia. In most cases, however, signs and symptoms appear between the ages of 5 and 15. The rate of disease progression varies. If you have Friedreich's ataxia, however, you're likely to rely on a wheelchair by your 30s, and your life span may be affected.

    The first indication generally is difficulty walking (gait ataxia). The condition typically progresses to the arms and trunk. Muscles weaken and waste away over time, causing deformities, particularly in your feet, lower legs and hands. Other signs and symptoms that may develop as the disease progresses include slow, slurred speech (dysarthria); fatigue; rapid, involuntary eye movements (mystagmus); spinal curvature (scoliosis) and heart disease, including heart enlargement (cardiomyopathy) and heart failure.

  • Ataxia-telangiectasia. This rare, progressive childhood disease causes degeneration in the brain and other body systems. The disease causes your immune system to break down (immunodeficiency disease), making you susceptible to diseases. It affects various organs.

    Telangiactasias are tiny red "spider" veins that may appear in the corners of your child's eyes or on the ears and cheeks. Although they're characteristic of the disease, your child may or may not develop them. Delayed motor skills development, poor balance and slurred speech are typically the first indications of the disease. Recurrent sinus and respiratory infections are common. About one in five children with ataxia-telangiectasia develop leukemia or lymphoma. Most people with the disease need a wheelchair by their teens and die in their 20s.

  • Congenital cerebellar ataxia. This type refers to ataxia that results from damage to the cerebellum that's present at birth.

  • Wilson's disease. People with this condition accumulate copper in their brains, livers and other organs, which can cause neurological problems, including ataxia.

Autosomal dominant ataxias
These include:

  • Spinocerebellar ataxias. To date, researchers have identified 28 autosomal dominant ataxia genes. The first was called spinocerebellar ataxia type 1 (SCA1), with subsequent ataxia genes generally numbered according to their order of discovery. Cerebellar ataxia and cerebellar degeneration are common to all types, but other signs and symptoms, as well as age of onset, differ depending on the specific gene mutation.

    The most common of the autosomal dominant ataxias in North America is SCA3, also known as Machado-Joseph disease. Onset can occur at any age, but most commonly occurs in the 30s and 40s. Signs and symptoms generally include speech and swallowing difficulties; eyelid retraction, which gives the impression that you're staring fixedly; and verbal and visual memory defects.

  • Episodic ataxia. There are two types of hereditary ataxias that are episodic rather than progressive. Type 1 involves brief ataxic episodes that may last seconds or minutes. Getting startled or exercising may bring on an episode. Type 2 involves longer episodes, which may last days. If you have this type of ataxia, you also may experience dizziness (vertigo), nausea, vomiting, headache and weakness during your episodes. Both types of episodic ataxia may respond to treatment with acetazolamide (Diamox), which also is used to treat seizures. Type 1 also may respond to the anticonvulsant phenytoin (Dilantin).

When to seek medical advice

If you lose muscle coordination in an arm or leg or slur your speech and aren't aware of having a condition, such as multiple sclerosis, that causes it, see your doctor.

Screening and diagnosis

Your doctor is likely to take a medical history, ask about when and how your ataxia developed and what signs and symptoms you're having, ask about drug and alcohol use and potential exposure to toxins, and conduct a physical exam and a neurological exam. A neurological exam includes checking your memory and concentration, vision, hearing, balance, coordination and reflexes.

In addition, to help determine the underlying cause, your doctor may request these laboratory tests:

  • Blood tests. Depending on what your doctor suspects is causing your ataxia, he or she may request certain blood tests to confirm or exclude the suspected condition. The specific tests will depend on the suspected cause, but most likely will include a complete blood count (CBC), which helps evaluate your overall health and detect a range of disorders, including infection and heavy metal poisoning.

  • Urine tests. Urinalysis may suggest certain systemic abnormalities that can be related to some forms of ataxia. If your doctor suspects Wilson's disease, you may be asked for a 24-hour urine collection to determine the amount of copper in your system.

  • Imaging studies. A computerized tomography (CT) scan or magnetic resonance imaging (MRI) of your brain may help determine potential causes.

  • Genetic testing. Your doctor may recommend genetic testing to determine whether you or your child has the gene mutation that causes one of the hereditary ataxic conditions.

Treatment

Treatment for ataxia depends on the underlying cause. There's no treatment specifically for ataxia. However, in some cases, such as ataxia that follows chickenpox or other viral infection, it's likely to resolve on its own over time.

For ataxia caused by conditions such as multiple sclerosis or cerebral palsy, ataxia might not be treatable. In that case, your doctor may be able to recommend adaptive devices that help you with your affected movements, such as a cane for walking or modified utensils for eating.

You also might benefit from certain therapies, such as physical therapy and occupational therapy to help your walking. If slurred speech is a problem, speech therapy may help. If your slurred speech is severe, your therapist may recommend communication aids, such as a speech synthesizer, an electronic device that turns written text into speech.

Coping skills

Living with ataxia can be extremely frustrating. The challenges ataxia represents, such as loss of independence, may lead to depression and anxiety. You may find that talking to a counselor or therapist can help you cope. Or you may find encouragement and understanding in a support group, either for ataxia or for your underlying condition, such as cancer or multiple sclerosis.

Although support groups aren't for everyone, they can be good sources of information. Group members often know about the latest treatments and tend to share their own experiences. If you're interested, your doctor may be able to recommend a group in your area.