Cerebellar ataxia is a loss of muscle coordination
caused by damage and/or degeneration of the
cerebellum or connections to it. The cerebellum is an
area in the back, bottom part of the brain that plays an
important role in movement and coordination. Thus,
damage/dysfunction of the cerebellum can negatively
impact the control one has over the strength, speed,
direction, range, and rhythm of muscle movements.
Areas connecting to the cerebellum that can cause
cerebellar ataxia are the pons, cerebellar peduncles,
red nucleus, and cerebellar peduncles.
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
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
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
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
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
viral disease. When cerebellar ataxia is caused by an infectious disease it is often referred to as post-
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
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."