Dandy-Walker malformation

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 4, 2017
StartDiseasesDandy-Walker malformation

Dandy-Walker malformation is a condition in which the brain of a developing fetus does not form properly. While not usually fatal, it can lead to severe developmental and physical problems that will provide lifelong challenges for the child and his or her parents. Its cause is not completely understood, but heredity seems to play a factor. 

Contents

Definition & Facts

Dandy-Walker malformation is one of several possible results of Dandy-Walker syndrome, a complex of conditions caused by failure of the cerebellum to form properly. DWS affects an estimated 1 in 30,000 births, but most children do not develop full malformation. The cerebellum, a structure in the lower back part of the brain, is responsible for motor control and language development, among other brain functions.

Dandy-Walker malformation is the most severe form of DWS. In the malformation, the cerebellum does not completely form. Instead, a large fluid-filled compartment forms at the back of the skull, and a cyst forms in the nearby fourth ventricle of the brain. Rarely, other brain malformations can occur at the same time including a shrunken or missing corpus callosum (the tissue joining the two halves of the brain) or an incompletely closed skull that allows the brain to protrude through the back of the head.

Dandy-Walker malformation can also cause defects elsewhere in the body, including the face and heart, and extremities including arms, legs, fingers, and toes. It is also sometimes accompanied by other sorts of birth defects, including cleft palate, kidney cysts, and other defects of the brain and spinal cord. In cases where there are multiple defects, it is often difficult for the fetus to survive outside the body. 

Symptoms & Complaints

Dandy-Walker malformation causes a variety of developmental delays. These can include early difficulty with motor control, such as sitting, standing, and walking, as well as problems breathing. Delays in developing speech are also common.

Children with DWM can also have vision problems and hearing problems, including an inability to control the movements of their eyes that results in jerky eye movements. Children suffering from DWM usually develop hydrocephalus (excessive cerebrospinal fluid, or "water on the brain") before age one. This excess fluid increases the pressure inside the skull and compresses the brain, which can lead to severe headaches, nausea and vomiting, excessive sleeping, and seizures.

It can also cause the head to become swollen and misshapen, since at that age the skull has not yet solidified enough to contain the pressure. If untreated, hydrocephalus can eventually damage the brain enough to cause permanent disabilities and even death.

Later in life, Dandy-Walker children continue to demonstrate a general loss of coordination, difficulties with balance, and impaired muscular development, and may have delayed puberty, seizures, and paralysis or stiffness. While it is rare, some children with DWM show no symptoms until late childhood or even later in life. 

Causes

The exact causes of Dandy-Walker syndrome are not completely understood. It is most likely the result of genetic defects in either or both parents that influence the development of the fetal brain. It often forms in children with trisomy 18, that is, an extra copy of chromosome 18, but can also be caused by extra copies of other chromosomes.

Although DWS has a genetic component, it does not seem to be hereditary; it does not run in families except in certain isolated cases. Another possibility is that it may be caused by external influences, including viral infections such as rubella and toxoplasmosis. Environmental toxicants and medications that tend to cause birth defects may also be responsible, as can diabetes in the mother.

Studies by the Centers for Disease Control and Prevention (CDC) have found that Dandy-Walker is more common among African-American mothers, mothers bearing twins, and women who have a history of fertility treatments. Girls are also more likely to develop DWS than boys. 

Diagnosis & Tests

Dandy-Walker syndrome can be diagnosed in the uterus by ultrasound screening or magnetic resonance imaging (MRI) of the fetus, which can reveal problems with the development of the brain. After birth, regular measurements of the baby's head circumference can reveal potential overgrowth that could be a sign of hydrocephalus.

Comparing the baby's development to a standard set of developmental milestones for motor control and intellectual development can also reveal whether there are any significant delays that might suggest irregularities in the brain.

If Dandy-Walker malformation is suspected, the doctor can use various imaging techniques, including X-rays, computed tomography (CT) scans and MRI scans, and cranial ultrasound to examine the structure of the skull and brain and identify unusual formations. 

Treatment & Therapy

Dandy-Walker malformation is not curable. However, once it has been identified, it is possible to treat its effects. In the case of hydrocephalus, the doctor may temporarily install an intracranial pressure monitor, which measures the pressure exerted by cerebrospinal fluid. If high pressure is detected, a cerebral shunt can be surgically installed to drain away the excess fluid and keep pressure within the skull at a normal level.

Anticonvulsant medication can be used to control seizures, and hearing aids and vision aids can help if the child has difficulty in those areas. A child with DWM will require therapy to provide support in needed ares, such as occupational therapy to improve strength, coordination, and motor skills, and speech therapy to help develop language abilities.

Some children with DWM develop normal intellectual abilities, while others have learning disabilities and will need special education to address them. While every case is different, children with DWM will likely need lifetime support and therapy in order to have a functional life, and those with multiple congenital defects will probably have shortened lifespans. 

Prevention & Prophylaxis

Since Dandy-Walker's causes are poorly understood but apparently genetic in nature, there is no real way to prevent it. Genetic counseling and genetic testing for the parents can help identify if risk factors are present, especially if the parents have already had a child with DWS.

Careful monitoring of fetal development, including regular ultrasounds, can help identify potential problems and allow the parents to make preparations.