Cerebellar Ataxia - MedFriendly.com

WHAT ARE SIGNS OF CEREBELLAR ATAXIA?

Cerebllar ataxia presents as wide-based type of gait (walking), in which one changes direction or falls

forward, backwards, or to the side. Someone with cerebellar gait walks in a staggered, shuffling,

unsteady, weak, slow, and irregular manner, with difficulty turning (sometimes resulting in falls). The feet

are faced outward and the person comes down first on the heel and then on the toes. Reaction time while

walking is usually diminished.

When evaluated, a person with cerebellar ataxia would have difficulty standing on one leg or walking with

one foot directly in front of the other with the toes of the back foot touching the heel of the front foot

(known as tandem gait). The wide-based nature of gait occurs as the condition worsens and the poor

coordination causes the person to appear to be taking higher steps than normal (known as high

steppage). In severe conditions, significant assistance (e.g., from others) and effort will be needed to walk

or even stand. Such patients may become confined to wheelchairs for safety reasons.

Other associated signs of cerebellar ataxia include sudden writhing movements in the limbs (arms or legs),

hypotonia, incoordination, and action/intention tremors. Hypotonia is abnormally decreased muscle tone

(tension). This can present as poor maintenance of posture, decreased resistance to slight pressure

exerted on the limbs, and delayed motor responses. Incoordination can present as delays in initiating

responses in limbs, errors in the force or range of movement, and errors in the rate and regularity of

movements. For example, when the person tries to reach for something, he or she may miss the target by

a significant degree.

There may be an inability to walk without support. Incoordination can cause an impaired ability to perform

rapid, alternating movements - a problem known as dysdiadochokinesia. Action tremors (also known as

intention tremors) are shaking movements that become worse when performing voluntary movements.

If the cerebellar vermis is involved (and adjacent areas near the middle of the cerebellum), this typically

presents as a "drunken sailor gait" (also known as drunken gait or reeling gait) which manifests as: a) an

unstable stance with the feet usually spaced widely apart (but they sometimes can be spaced narrowly),

b) unsteady (e.g., backwards and forwards, side to side), uncertain, and irregular walking, and c) high

steps placed carefully with the person looking forwards. The cerebellar vermis is a narrow, worm shaped

structure in between both sides of the cerebellum. Each time the person with drunken gait rocks back and

forth or side to side, it seems that he/she is going to fall, and it often seems like the person is indifferent to

this. However, sometimes the person can correct the abnormal walking, depending on the level of

drunkenness. The person may fall to the side of where the cerebellar damage is located. People with

drunken gait often have nystagmus, which is rhythmic involuntary jerking or swinging movements of the

eyes.

The most severe disturbances in cerebellar ataxia are caused by damage to the superior (top) cerebellar

peduncles and the red nucleus. See the first section for a description of the cerebellar peduncles and red

nuclei.

IS CEREBELLAR ATAXIA COMMONLY SEEN IN CERTAIN MEDICAL CONDITIONS?

Yes, cerebellar ataxia is common in some medical conditions, such as alcoholism, brain tumors, inherited

abnormalities, and multiple sclerosis. Multiple sclerosis is a condition in which the body attacks its own

myelin, resulting in multiple areas of abnormal patches (also known as plaques or sclerosis) in the brain

and/or spinal cord. Myelin is a fatty substance in the brain and spinal cord that helps transmit nerve

impulses quickly.

Sometimes, cerebellar ataxia can occur after certain viral infections in childhood, such as chicken pox and

Miller Fisher syndrome. Miller Fisher syndrome is a rare, inherited disorder characterized by abnormal

muscle coordination, paralysis of eye muscles, and absence of the tendon reflexes. Tendons are groups

of fibers that attach muscles to a bone. Diseases of the thyroid gland can sometimes cause cerebellar

ataxia. The thyroid gland is a butterfly-shaped organ located in the front of the neck that plays an

important role in metabolism. Metabolism is the chemical actions in cells that release energy from

nutrients or use energy to create other substances.

AT WHAT AGE DOES CEREBELLAR ATAXIA OCCUR?

Cerebellar ataxia can occur at any age, from childhood to adulthood. When the condition occurs in

childhood, it is more likely caused by an inherited abnormality. That is, the condition is passed on from the

genes of the parents. Genes are units of material contained in a person's cells that contain coded

instructions for how certain bodily characteristics (such as eye color) will develop. All of a person's genes

come from his/her parents. Genes are contained in structures called chromosomes.

Most inherited cases of childhood cerebellar ataxia are autosomal recessive. To understand what this

means, consider the following. Genes can either be dominant or recessive. A gene that masks the effect

of another gene is called a dominant gene. The gene whose expression is masked is known as a

recessive gene. Each person has 23 pairs of chromosomes. One of each pair of chromosomes is

inherited from the mother and one of each pair is inherited from the father. The first 22 pairs of

chromosomes (known as autosomes) are not involved in determining sex. If a condition is caused from a

recessive gene on one of the first 22 pairs of chromosomes (autosomes), the condition is called

autosomal recessive.

The 23rd pair of chromosomes, however, is involved in determining sex. The 23rd pair of chromosomes

consist of X and/or Y chromosomes. An X chromosome is shaped like an X, whereas a Y chromosome is

shaped like a Y. If a person has two X chromosomes, the person will develop as a female. If a person has

an X and a Y chromosome, the person will develop as a male. There have been rare cases, where

cerebellar ataxia has been traced back to being caused by a problem with the X chromosome.

ARE THERE DIFFERENT TYPES OF CEREBELLAR ATAXIA?

Yes, there are different types of cerebellar ataxia. The different types are classified according to the

cause and specific location of the body affected. However, the different types of cerebellar ataxia do not

vary much in terms of clinical signs and symptoms. As an example of some different types of cerbellar

ataxia, acute cerebellar ataxia is a sudden onset of impaired coordination, often following an infectious

viral disease. When cerebellar ataxia is caused by an infectious disease it is often referred to as post-

infectious cerebellar ataxia.

Aniridia-cerebellar ataxia-mental deficiency (also known as Gillespie Syndrome), is a very rare inherited

disorder characterized by partial absence of the colored portion of the eye, impaired coordination of

voluntary movements due to underdevelopment of the cerebellum, and mental retardation. Many affected

individuals also have a delay in acquiring skills that require coordination of muscles. Aniridia-cerebellar

ataxia-mental deficiency is believed to be autosomal recessive (see prior section).

CAN INHERITED FORMS OF CEREBELLAR ATAXIA BE PREVENTED?

Inherited forms of cerebellar ataxia caused by abnormalities on the X-chromosome (see above) can

sometimes be avoided through genetic testing. The first step of the process is for concerned parents to

go to genetic counseling. Genetic counseling is the process of evaluating family history and medical

records, ordering genetic tests, and evaluating the results to help parents understand and reach decisions

about whether to have children.

For families with cerebellar ataxia caused by an abnormality on the X-chromosome, a form of testing

known as preimplantation genetic diagnosis (PGD) may be helpful. PGD tests for genetic abnormalities in

the embryo before it implants in the uterus. An embryo is a fertilized egg from the time of conception until

the 8th week of pregnancy. The uterus is a hollow organ in a female's body where the egg is implanted

and the baby develops.

PGD can also tell the embryo's gender. This is helpful because implanting only those embryos into the

uterus whose gender is less likely to develop the disease will greatly reduce the chance of having an

affected child. In the case of cerebellar ataxia due to abnormalities on the X-chromosome, girls would be

less likely to develop the disease. An experienced genetic counselor should be able to advise if PGD will

be helpful.

WHAT ELSE IS CEREBLLAR ATAXIA KNOWN AS?

Cerbellar ataxia is also known as cerebellar gait and ataxic gait.

WHAT IS THE ORIGIN OF THE TERM, CEREBELLAR ATAXIA?

Cerebellar ataxia comes from the Latin word "cerebellum" meaning "little brain," the word "a" meaning "no,"

and the word "taxis" meaning "order." Put the words together and you get "no order little brain."