The cyst that is present in Dandy Walker syndrome begins to form long before the baby is born, when it is inside of the mother. The cyst can eventually grow to such a size that it lifts up and distorts the cerebellum. An area in the cerebellum known as the vermis is either partially incomplete or totally missing in Dandy Walker syndrome. The vermis of the cerebellum is a wormlike appearing structure in the middle of the cerebellum. The vermis plays an important role in controlling the posture and tension of muscles.

The cerebellum and other some other important lower brain structures rest in an indented area of bone in the lower, back part of the skull known as the posterior cranial fossa. The posterior cranial fossa becomes larger in patients with Dandy Walker syndrome. In addition, people with Dandy Walker syndrome can develop cysts can in the posterior cranial fossa.

WHAT ARE SOME OTHER BRAIN ABNORMALITIES PRESENT IN DANDY WALKER SYNDROME?

In addition to the abnormalities mentioned in the previous section, there are other brain abnormalities that are sometimes present in Dandy Walker syndrome. In some individuals, the cyst that forms in the fourth ventricle (see above) closes two normal openings in that ventricle. These two openings are known as the foramen of Luschka and the foramen of Magendie. As a result, the cerebrospinal fluid that is in the fourth ventricle cannot escape out of those openings and the fluid builds up, causing hydrocephalus. Hydrocephalus is a condition in which there is an abnormal increase in cerebrospinal fluid inside the head.

Another characteristic is the partial or total absence of the corpus callosum, which is a large band of nerve fibers in the brain that help the two sides of the brain communicate with each other. A partial absence of the corpus callosum is common in Dandy Walker Syndrome. Heterotopia can be present as well. Heterotopia refers to when gray matter (a gray appearing substance) in the brain is out of its normal place and has typically made its way into the white matter (a white appearing substance) of the cerebrum, where it should not be. The cerebrum is the top section of the brain.

Other brain abnormalities include an absence of gyri (rounded elevations) or abnormally small gyri. Gyri are normally present on the brain and help increase its surface area (the total area exposed on the surface).

WHAT ARE THE SIGNS AND SYMPTOMS OF DANDY WALKER SYNDROME?

It is important to note that the signs and symptoms of Dandy Walker Syndrome can occur suddenly or never occur at all. In fact, sometimes Dandy Walker syndrome is not diagnosed until the person reaches adulthood, although most people are diagnosed by age one. The following is a list of some signs and symptoms that can occur in Dandy Walker syndrome. The list is variable and does not occur in all people affected with this condition.

Most of the signs and symptoms of Dandy Walker syndrome are due to a buildup of cerebrospinal fluid in the head, a condition known as hydrocephalus. Hydrocephalus is usually accompanied by increased pressure within the bones that surround the brain. This pressure can also cause the sutures (places where two bones join together) of the skull to separate, resulting in an abnormally large skull. Sometimes this is the only sign of Dandy Walker syndrome, and it can happen rapidly. The "soft spot" in infants, which is the area where the skull bones have not yet closed together, can bulge outwards.

People with hydrocephalus have a thin scalp (the skin that covers the skull). As a result, the veins in the scalp are easily seen in people with hydrocephalus. Also, as was mentioned earlier, infants sometimes have a difficult time moving their head if they have an abnormal buildup of fluid in it. They may also have a poor control of their neck muscles. Some people with Dandy Walker syndrome experience titubation, which is an unsteady posture characterized by staggering or stumbling while walking and swaying of the head and upper part of the body while sitting.

Because of the incomplete development of the cerebellum, which is important for controlling motor abilities, infants with Dandy Walker syndrome tend to display poor motor development. For example, many children with Dandy Walker syndrome have a very difficult time walking. Many people with Dandy Walker syndrome also have spasticity. Spasticity is a condition in which there is increased tension in muscles that resist the force of gravity (the natural force that pulls objects downwards) and increased resistance to stretch.

In older children with Dandy Walker Syndrome, increased pressure in the head can cause irritability, vomiting, and convulsions (abnormal, severe, involuntary muscle movements). Approximately 20 to 30% of children with Dandy Walker syndrome experience seizures, which are involuntary muscle movements and/or decreased awareness of the environment due to overexcitement of nerve cells in the brain. Incomplete development of the cerebellum in older children with Dandy Walker syndrome can cause impaired motor coordination, imbalance, dizziness, and uncontrollable jerky eye movements.

Some other problems with the eyes that can occur in people with Dandy Walker syndrome include catracts, retinal dysgenesis, and choroid coloboma. Cataracts is a darkening of the lens in the eye(s). The lens is an organ located between the colored part of the eye, that bends light as it enters the eye. Retinal dysgenesis is an abnormal formation of the retina that occurs when the baby is developing inside of the mother. The retina is an area at the back of the eye that is sensitive to light. Choroid coloboma is a birth defect in which the choroid of the eye is not formed properly. Choroid is a layer in the eye between the sclera (the outer, white part of the eye) and the retina. All of these abnormalities of the eye make it difficult to see.

Some people with Dandy Walker syndrome have sleep apnea, which is a disorder in which the person does not breath for periods of time while sleeping. Other signs and symptoms of Dandy Walker syndrome include increased head size, a bulge in the back of the head, abnormal breathing, and poor functioning of the cranial nerves. Cranial nerves are nerves that emerge from the brain. Approximately 30% of children with Dandy Walker syndrome have abnormal formations of the face, heart, fingers, face, arms, and/or legs. One type of abnormality is the hands and feet is the presence of more than the normal number of fingers or toes. In some cases, two are more fingers are joined together.

One type of facial abnormality is cleft lip. In cleft lip, the upper lip has not formed properly and there are one or more openings in it. Cleft palate, which is an incomplete formation of the roof of the mouth, is also seen in some cases of Dandy walker syndrome. The incomplete formation in cleft palate is characterized by a groove in the middle of the roof of the mouth.

Some people with Dandy Walker have abnormalities in the structure of the urinary tract. The urinary tract is the part of the body that deals with the formation and excretion of urine (pee). To excrete means to release from the body as waste. An example of such an abnormality would be polycystic kidney, a condition in which the kidneys are too large and contain many cysts on them. The kidneys are two organs located on each side of the spine, behind the stomach. The kidneys filter (remove) wastes from the blood.

IS THE SPINE EVER AFFECTED IN DANDY WALKER SYNDROME?

Yes, but not always. Sometimes, the cyst along the fourth ventricle (see previous sections) extends into the opening where the spinal cord is located. A condition that affects the spinal cord, which is associated with Dandy Walker syndrome is syringomyelia. Syringomyelia is a condition in which long, fluid filled spaces are present in the central gray matter (a gray looking substance) of the spinal cord and surrounded by thick tissues made of glial cells. Glial cells are supportive cells. The long, fluid filled spaces look like tubes in the spinal cord. It can also look like one big tube in the spinal cord.

The vertebrae in the lower part of the spine can be abnormal in people with Dandy Walker syndrome. Vertebrae are bones that form an opening in which the spinal cord passes.

WHAT IS THE INTELLIGENCE LEVEL OF PEOPLE WITH DANDY WALKER SYNDROME?

Unfortunately, many children with Dandy Walker syndrome suffer from mental retardation. However, 50% of children with Dandy Walker syndrome have normal cognitive functioning.

WHAT CAUSES DANDY WALKER SYNDROME?

In most cases, the cause of Dandy Walker syndrome is unknown. It has been suggested that abnormalities in chromosomes may cause some cases of Dandy Walker syndrome. Chromosomes are structures in a person's cells that contain genes. Genes are units of material that contain coded instructions as for how certain bodily characteristics (such as eye color) will develop. All of a person's genes come from his/her parents. Some genes are normal whereas others may be abnormal. Abnormal genes can cause diseases.

It has also been suggested that Dandy Walker syndrome can be caused by exposure to an anti-acne (anti-pimple) medication called isotretinoin during the first three months that the baby is developing inside the mother.

HOW IS DANDY WALKER SYNDROME DIAGNOSED?

Dandy Walker syndrome is diagnosed with X-rays and a CT (computerized tomography) scan of the brain. CT scanning is a more advanced imaging technique that uses x-rays and computer technology to produces more clear and detailed pictures than a traditional x-ray. Magnetic resonance imaging (MRI) scans of the brain can also be used. MRI scans produce extremely detailed pictures of the inside of the body by using very powerful magnets and computer technology. MRI scans are more detailed and more expensive that CT scans. A rarely used technique to diagnose Dandy Walker syndrome is a ventriculogram. A ventriculogram is a specific x-ray study of the ventricles in the brain. Ventricles are openings in the brain that produce the cushiony fluid that protects the brain and spine.

WHAT IS THE AGE OF MOST PEOPLE WHEN DIAGNOSED WITH DANDY WALKER SYNDROME?

Approximately 80% of children that are diagnosed with Dandy Walker syndrome receive this diagnosis by age 1. The diagnosis is usually made this early because of the enlarged head caused by the buildup of cerebrospinal fluid. This buildup of fluid often makes it difficult for the infant to control his/her head, which usually leads parents to bring the child in to the doctor for an evaluation.

HOW IS DANDY WALKER SYNDROME TREATED?

Unfortunately, as of yet, there is no way to reverse the main structural abnormalities caused by Dandy Walker syndrome. However, some of the other abnormalities associated with this condition can be treated. For example, physical therapy is often used to help patients improve their abnormal motor functioning. However, many individuals will still continue to have difficulty walking and have poor balance. Another treatment is to give medication to reduce seizures. Seizures are involuntary muscle movements and/or decreased awareness of the environment due to overexcitement of nerve cells in the brain.

To treat the buildup of fluid in the head, a flexible tube called a shunt can be placed in the ventricles of the brain, the inside of the brain, or the posterior fossa (the indented bone in the lower, back part of the skull). From one of these areas, the tube will drain the extra fluid into the space between layers that line the belly. The fluid will then be absorbed along the wall of the belly.

The shunting procedure will decrease the pressure in the head and will thus prevent the head from widening further. Sometimes, more than one tube needs to be placed, such as a tube in a ventricle and a tube in the posterior fossa. If these two spaces are not connecting, the surgeon will connect the tubes to a common valve that drains the fluid.

WHY CAN'T THE CYST BE REMOVED?

The cyst cannot be removed with surgery because it already has blood vessels that go through it and connect to the brain. Taking out the cysts would thus cause too much damage to the brain.

HOW MANY CHILDREN ARE BORN WITH DANDY WALKER SYNDROME?

Dandy Walker Syndrome is rare, occurring in about 1 out of every 25,000 to 30,000 births.

IS DANDY WALKER SYNDROME SEEN MORE IN MALES OR FEMALES?

Although some studies report that approximately equal numbers of males and females are affected with Dandy Walker Syndrome, others report that more females are affected than males.

WHAT IS THE PROGNOSIS OF PEOPLE WITH DANDY WALKER SYNDROME?

The prognosis of people with Dandy Walker syndrome is variable, even when the buildup of fluid in the head is correctly treated at an early stage. Generally, the more severe the defects, the worse intellectual abilities and the less likely the chance of survival will be.

WHAT ELSE IS DANDY WALKER SYNDROME KNOWN AS

Dandy Walker syndrome is also known as Dandy Walker, Dandy Walker cyst, Dandy Walker variant, and Dandy Walker malformation.

WHAT IS THE ORIGIN OF THE TERM, DANDY WALKER SYNDROME

Dandy Walker syndrome was named after two physicians, Walter E. Dandy and Arthur E. Walker. Walker was an American surgeon who lived from 1907 to 1995. Dandy was an American neurosurgeon who lived from 1886 to 1946. Neurosurgeons operate on the brain, spine, and/or nerves outside the brain and spine.

It is interesting to note, however, that the condition was fist described by Dandy and a U.S. physician named Kenneth Blackfan in 1914. Blackfan lived from 1883 to 1941. Dandy and Blackfan described the case of a 13-year-old child with an abnormally high amount of cerebrospinal fluid in the head, cysts in the back of the skull, and an incompletely developed vermis of the cerebellum. Please see the beginning of this entry for a description of these terms.

Many years went by and it 1942, Arthur Walker and his colleague, Johhn Taggart, gave a talk in which they described nine cases (including the one described by Walker and Blackfan) in which children were born with the similar signs mentioned above. The term, "Dandy-Walker syndrome" was first used in 1954 by C. E. Benda in a paper he published entitled, "The Dandy-Walker syndrome or the so-called atresia of the foramen of Magendie." The article was published in the Journal of Neuropathology and Experimental Neurology, Volume 13, pages 14-39.