vWhat Is Ataxia? What Causes Ataxia?

Editor's Choice Main Category: Neurology / Neuroscience Also Included In: Multiple Sclerosis; Muscular Dystrophy / ALS Article Date: 31 Aug 2009 - 0:00 PDT email to a friend
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Ataxia is a lack of muscle coordination which may affect speech, eye movements, the ability to swallow, walking, picking up objects and other voluntary movements. A person with persistent ataxia may have damage in the part of the brain that controls muscle coordination - the cerebellum. Ataxia may have several causes, includingmultiple sclerosis, a head injury, alcohol abuse, stroke, cerebral palsy, a faulty gene, or a tumor. Ataxia may also be a symptom of incoordination linked to infections. There are different types of ataxias including Friedreich's ataxia and spinocerebellar ataxia type 6. A less common type is ataxia telangiectasia. According to Ataxia UK, there are over 40 known forms of inherited ataxias - new forms continue to be identified as scientific techniques improve. The International Ataxia Awareness Day is observed on September 25 each year. According to Medilexicon's medical dictionary, ataxia is " An inability to coordinate muscle activity during voluntary movement; most often results from disorders of the cerebellum or the posterior columns of the spinal cord; may involve the limbs, head, or trunk." The term ataxia may also be used more broadly to indicate a lack of coordination in a physiological process, such as optic ataxia (usually part of Balint's syndrome which includes a lack of coordination between visual inputs and hand movements), or ataxic respiration (uncoordinated respiratory movements, usually due to dysfunction of the respiratory centers of the medulla oblongata). The English word "ataxia" comes from the Ancient Greek word ataksia meaning "disorder". The Ancient Greek word taksia means "order".

Some types of ataxias

Cerebellar ataxia This is ataxia caused by a dysfunction of the cerebellum - a region in the brain which is involved in the assimilation of sensory perception, coordination and motor control. Cerebellar ataxia causes some basic neurological problems, such as: Floppiness (hypotonia). Lack of co-ordination between organs, muscles, limbs or joints (asynergy). Impaired ability to control distance, power, and speed of an arm, hand, leg or eye movement (dysmetria). Difficulty in accurately estimating how much time has passed (dyschronometria). An inability to perform rapid, alternating movements (dysdiadochokinesia). How the patient is affected depends on which parts of the cerebellar are lesioned, and whether lesions occur on one side (unilateral) or both sides (bilateral).

If the vestibulocerebellum is affected the patient's balance and eye movement control will be affected. The patient will typically stand with feet wide apart in order to gain better balance and avoid swaying backwards and forwards (posterior-anterior oscillations). Even when the patient's eyes are open balance is difficult when the feet are together. If the spinocerebellum is affected the patient will have an unusual gait, with unequal steps, sideways steps, and uncertain starts and stops. The spinocerebellum regulates body and limb movements. If the cerebrocerebellum is affected the patient will have problems carrying out voluntary, planned movements. The head, eyes, limbs and torso may tremble as voluntary moves are carried out. Speech may be slurred, with variations in rhythm and loudness. Sensory ataxia This is ataxia due to loss of proprioception. Proprioception is the sense of the relative position of neighboring parts of the body. It is a sense that indicates whether the body is moving with the required effort, and also where the various parts of the body are located in relation to each other. Even if I am blindfolded I know through proprioception if my arm is above my head or hanging down in front of me, by my side, or behind me. A patient with sensory ataxia typically has an unsteady stomping gait, with the heel striking hard as it touches the ground with each step. Postural instability becomes worse in poorly lit environments. If a doctor asks the patient to stand with eyes closed and feet together his/her instability will clearly worsen. This is because loss of proprioception makes the patient much more reliant on visual data. The patient may find it hard to perform smoothly coordinated voluntary movements with the limbs, trunk, pharynx, larynx, and eyes. Vestibular ataxia The vestibular system is affected. In acute (sudden) unilateral cases the patient may experience vertigo, nausea, and vomiting. In slow-onset chronic bilateral cases the patient may only experience unsteadiness, giddiness.

What are the symptoms of ataxia?

Symptoms may vary depending on the severity and type of ataxia, of which there are many. If the ataxia is caused by an injury or another health condition, symptoms may emerge at any age, and may well improve and eventually disappear. Initial ataxia symptoms usually include: Poor limb coordination. Dysarthria - slurred and slow speech that is difficult to produce. The patient may also have difficulties controlling volume, rhythm, and pitch. If the ataxia advances other symptoms may also appear: Swallowing difficulties, which may sometimes result in choking or coughing. Facial expressions become less apparent. Tremors - parts of the body may shake or tremble unintentionally. Nystagmus - involuntary rapid rhythmic repetitious eye movement. Movements may be vertical, horizontal, or circular. Pes cavus - a foot with too high an arch. Cold feet - because of a lack of muscle activity. Problems with balance. Walking difficulties - in severe cases the patient may need a wheelchair.

Vision problems. Hearing problems. Depression - as a result of having to live and cope with the symptoms. Cerebellar ataxias Cerebellar ataxia early onset usually emerges between the ages of 4 and 26. Late onset ataxia generally appears after the patient is 20 years old. Late-onset ataxias usually present less severe symptoms, compared to early-onset ataxia. Ataxia telangiectasia symptoms generally include:

Small veins appear around the corner of the eyes, cheeks and ears. Physical and sexual development is usually delayed. Friedreich's ataxia symptoms generally include:

The spine curves sideways (scoliosis). The heart muscle becomes weaker (cardiomyopathy). Diabetes. For patients whose symptoms are caused by injury or illness, symptoms often improve over time, and eventually go away completely.

What are the causes of ataxia?

Vitamin B12 deficiency - as well as other neurological abnormalities, vitamin B12deficiency can cause overlapping cerebellar and sensory ataxia. Ataxia can be a symptom of another health condition, it can also be inherited or non-inherited. Inherited ataxia This means the ataxia is caused by a genetic fault inherited either from the mother or father, or both. A faulty gene that is passed down through generations can cause cerebellar ataxia - in some cases its severity worsens from one generation to the next and the age of onset gets younger. This type of worsening inherited ataxia is known as anticipation. The chances of inheriting ataxia from a parent depends on the type of ataxia that parent has. For a person to develop Friedreich's ataxia the faulty gene would need to be carried by both the mother and the father (recessive inheritance). Spinocerebellar ataxia, on the other hand, only requires one parent to carry the defective gene (dominant inheritance), and each of his/her offspring would have a 50% risk of developing the condition. Non-inherited ataxia Even without a family history of ataxia some people may still develop the condition. In some cases, experts never find out what the cause was. The following procedures and circumstances can cause ataxia: Brain surgery. Head injury. Alcohol abuse. Drug abuse. Infections, such as chicken pox (usually goes away after infection has gone). A brain tumor. Exposure to toxic chemicals.

Multiple sclerosis, cerebral palsy, and some other neurological conditions. Malformation of the cerebellum while the baby is still in the womb.

How is Ataxia diagnosed?

A doctor who suspects the patient may have ataxia will refer him/her to a neurologist - a doctor specialized in diagnosis, treatment and prevention of conditions and illnesses related to the nervous system. The specialist will check the patient's medical history for cause factors, such as brain injury, as well as the patient's family history for indications of inheritance. The following tests may also be ordered: Magnetic resonance imaging (MRI) or Computerized Tomography (CT) scan - to determine whether there is any brain damage.

Genetic tests - to determine whether the patient has inherited ataxia.

Blood tests - some types of ataxia affect the make up of blood.

Urine tests - urinalysis may suggest specific systemic abnormalities that are linked to some forms of ataxia. If the specialist suspects Wilson's disease the patient may be asked for a 24-hour urine collection to determine how much copper is in the system. In some cases the specialist never knows what caused the ataxia, this is known assporadic or idiopathic ataxia. Reaching a conclusive diagnosis of ataxia can sometimes take a long time because the symptoms could point to several other conditions.

What is the treatment for ataxia?

Although ataxia is not curable, a great deal can be done to ease symptoms and improve the quality of life of the patient. Treatment for coordination and balance problems usually involves the use of adaptive devices which help the patient attain as much independence as possible. These may include the use of a cane (walking stick), crutches, walker or a wheelchair. Symptoms such as tremor, stiffness, spasticity, sleep disorders, muscle weakness, depression (or frustration, sadness and anger) may be addressed with targeted physical therapy, speech therapy, medications and counseling. Occupational therapy - the occupational therapist can help the patient manage better around the house and work. This may involve some home adaptations, wheelchair assessments, and making the kitchen more practical for the patient.

Speech therapy - the speech therapist can help with swallowing, coughing, choking and speech problems. If speech becomes very difficult the speech therapist can help the patient learn how to use speech aids.

Orthopedic care - this can help patients with curvature of the spine (scoliosis).

Physical therapy (physiotherapy) - a physical therapist (physiotherapist) can help maintain strength and improve mobility.

Counseling - patients with ataxia commonly become frustrated and depressed; this usually results from having to cope with some symptoms which affect physical mobility and coordination. Talking to a well qualified counselor, such as a psychotherapist can help.

Supplements and nutrition - some patients with ataxia have very low levels of vitamin E and require supplements and/or a special diet. As sensitivity to gluten is more common among ataxia patients, a gluten-free diet also helps.

Medication - some patients with ataxia telangiectasia are prescribed gamma-globulin injections to boost their immune systems. There are also drugs for muscle spasms and uncontrollable eye movements.

Causes of ataxia
Ataxia is caused by damage to the spinal cord and a part of the brain known as the cerebellum. The spinal cord is a cable of nerves that runs from the brain to the rest of the body. The cerebellum sits at the base of the brain (the brainstem) and is responsible for controlling: physical movement, co-ordination, and spatial awareness (awareness of your surroundings in the relation to yourself).

In cases of acute ataxia, the spinal cord and cerebellum can be damaged by factors such as: physical trauma, infection, and loss of blood supply.

In cases of hereditary ataxia, the spinal cord and cerebellum are damaged slowly, over time, as the genetic mutations that are associated with hereditary ataxia interfere with the normal development of the brain and nervous system. This leads to progressive brain and neurological damage. Different mutations can affect the brain and nervous system in different ways, but what they usually have in common is that they interfere with the normal production of proteins which results in damage to nerve cells.

For example, Friedreichs ataxia is caused by a mutation in a gene known as the GAA gene. This mutation results in the body not producing enough of a protein called frataxin. Frataxin is thought to play a role in the regulation of iron levels inside nerve cells. As not enough frataxin is being produced, the level of iron and other toxic substances starts to build up inside the nerve cells, damaging them.

The genetics of ataxia

In order to gain a better understanding of the genetics of hereditary ataxia, it is useful to learn about chromosomes. Chromosomes are blocks of deoxyribonucleic acid (DNA). They contain a detailed set of instructions that control a wide range of factors - from how the bodys cells develop, to what colour eyes a baby will have, and what sex a baby will be. You receive two sets of chromosomes - one from your mother and one from your father. As all the genes in your body are created from these chromosomes, you will receive two sets of every gene one gene from your mother and one gene from your father. There are two ways that a genetic mutation can be passed down through families: autosomal recessive - such as the mutation that is responsible for Friedreichs ataxia , and autosomal dominant - such as the mutation that is responsible for spinocerebellar ataxia.

Autosomal recessive
If the mutated gene is autosomal recessive, it means that you will only develop ataxia if you receive a pair of mutated genes (one from your mother and one from your father). If you only receive one of the mutated genes, the other normal gene will cancel out the effects of the mutation. However, you will be a carrier of one of the mutated genes. It is estimated that 1 in every 80 people are carriers of a mutated ataxia gene. If two carriers have a baby: there is a 25% chance that the baby will receive a pair of normal genes, there is a 50% chance that the baby will receive one normal gene and one mutated gene; in this case, they will not develop ataxia, but they will be a carrier, and there is a 25% chance that the baby will receive a pair of mutated genes and will develop ataxia. If you have autosomal recessive ataxia, and your partner is a carrier: there is a 50% chance that your baby will receive one normal gene and one mutated gene and become a carrier, and there is a 50% chance that your baby will receive a pair of mutated genes and develop ataxia.

If you have autosomal recessive ataxia and your partner is not a carrier, there is no risk that any children that you have will develop ataxia because your mutated gene will be cancelled out by your partners normal gene.

Autosomal dominant
If the mutated gene is autosomal dominant, you can develop ataxia if you receive a single mutated gene, either from your mother or your father. This is because the mutation is strong enough to override the other, normal gene. If you have autosomal dominant ataxia, any children that you have will have a 1 in 2 chance of developing ataxia.

Genetics and pregnancy

There are a number of tests that can be used to check whether your partner is a carrier of any of the autosomal recessive ataxia genes, so that you can better estimate the risk of having a baby with ataxia. Testing should also be able to detect if a pregnancy will result in the baby being born with autosomal dominant ataxia. These types of tests are known as genetic counselling. Your GP should be able to arrange for you to be referred to a regional genetic centre where counsellors will be able to carry out the tests and explain the implications of the results to you. Alternatively, the Genetics Interest Group (GIG) provides information about the genetic services that are available in England.

Exogenous substances
Exogenous substances that cause ataxia mainly do so because they have a depressant effect on central nervous system function. The most common example is ethanol, which is capable of causing reversible cerebellar and vestibular ataxia. Other examples include various prescription drugs (e.g. most antiepileptic drugs have cerebellar ataxia as a possibleadverse effect), cannabis ingestion
[2]

and

various other recreational drugs (e.g. ketamine, PCP or dextromethorphan, all of which are NMDA receptor antagonists that produce a dissociative state at high doses). [edit]Vitamin

B12 deficiency

Vitamin B12 deficiency may cause, among several neurological abnormalities, overlapping cerebellar and sensory ataxia. [edit]Causes

of isolated sensory ataxia

Peripheral neuropathies may cause generalised or localised sensory ataxia (e.g. a limb only) depending on the extent of the neuropathic involvement. Spinal disorders of various types may cause sensory ataxia from the lesioned level below, when they involve the dorsal columns. [edit]Non-hereditary

cerebellar degeneration

Non-hereditary causes of cerebellar degeneration include chronic ethanol abuse, paraneoplastic cerebellar degeneration, high altitude cerebral oedema, coeliac disease, normal pressure hydrocephalus and cerebellitis.

[edit]Hereditary

ataxias

Ataxia may depend on hereditary disorders consisting of degeneration of the cerebellum and/or of the spine; most cases feature both to some extent, and therefore present with overlapping cerebellar and sensory ataxia, even though one is often more evident than the other. Hereditary disorders causing ataxia include autosomal dominant ones such asspinocerebellar ataxia, episodic ataxia, and dentatorubropallidoluysian atrophy, as well as autosomal recessive disorders such as Friedreich's ataxia (sensory and cerebellar, with the former predominating) and Niemann Pick disease, ataxiatelangiectasia (sensory and cerebellar, with the latter predominating), and abetalipoproteinaemia. An example of X-linked ataxic condition is the rare fragile X-associated tremor/ataxia syndrome. [edit]Arnold-Chiari

Malformation

Arnold-Chiari malformation is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsils and the medulla through the foramen magnum, sometimes causing hydrocephalus as a result of obstruction of CSF (cerebrospinal fluid) outflow.