Dandy-Walker complex is a group of disorders that affect the development of the brain. The changes in brain development are present from birth (congenital). Dandy-Walker complex affects the formation of the area of the brain known as the cerebellum, which is responsible for coordinating movement, and the fluid-filled spaces around it. People with Dandy-Walker complex may have a portion of the brain called the cerebellar vermis that is smaller than expected (hypoplastic) or completely absent (aplastic). The cerebellar vermis is the area of the brain between the two halves of the cerebellum. People with Dandy-Walker complex have a larger than expected fourth ventricle of the brain. This ventricle allows fluid to flow between the upper and lower areas of the brain and spinal cord. People with Dandy-Walker complex may have an enlarged portion of the base of the skull (posterior fossa). Dandy-Walker complex may be more common in females than in males.

Dandy-Walker complex is a group of disorders that have overlapping symptoms. These disorders include:

• Dandy-Walker malformation (also known as Dandy-Walker syndrome): having a small cerebellar vermis, large fourth ventricle, and enlarged posterior fossa
• Isolated cerebellar vermis hypoplasia (sometimes known as Dandy-Walker variant): having a small cerebellar vermis without other features of Dandy-Walker complex
• Mega-cisterna magna: having an enlarged posterior fossa with a typically developed cerebellum. This may be a normal variant and may not cause any health problems.
• Posterior fossa arachnoid cyst: the development of a cyst on the posterior fossa without any other features of Dandy-Walker complex

Each of these disorders can have separate causes and different long-term outlooks. In order to provide families with more information about the specific developmental differences in the brain and the long-term outlook, a person with Dandy-Walker complex may be given a more specific diagnosis.

In some cases, Dandy-Walker complex is caused by an underlying genetic change. These genetic changes may cause Dandy-Walker complex alone, or they may cause Dandy-Walker complex as well as other health problems. In these situations, the complex can run in families. However, in most situations, Dandy-Walker complex is caused by a combination of genetic and environmental factors. Dandy-Walker complex can be diagnosed by imaging of the brain such as ultrasound, CT scan, or MRI scan. Treatment options may include a surgery to place a ventriculoperitoneal shunt that relieves excess fluid from the brain, as well as physical and occupational therapies.

Dandy-Walker syndrome is a neurological disorder caused by an unusual formation between the cerebellum and the fluid-filled spaces around it. The cerebellum is in the back part of the brain and controls movement. The disorder is sometimes associated with an absence of the corpus callosum, which is the area made up of nerve fibers connecting the two sides of the brain. Symptoms of Dandy-Walker syndrome may include:

In babies:

• Slow development of motor skills (the ability to control movements)
• Progressive growth of the skull

In older children:

• Pressure in the skull
• Irritability
• Throwing up
• Having a hard time with balance or controlling muscle movements
• Unusual eye movements

Dandy-Walker syndrome can cause unusual development of the head, heart, face, arms, or legs—although some children may never have symptoms. Treatment focuses on symptoms. Surgery may help get rid of extra fluid that causes some of the symptoms, and physical and other forms of therapy can help with managing symptoms.

Dandy-Walker (DW) malformation refers to a developmental abnormality of the brain generally characterized by 3 main findings:

• cystic dilation (enlargement) of the fourth ventricle (one of the fluid-filled cavities within the brain)
• complete or partial agenesis (absent development) of the cerebellar vermis (structure between both sides of the cerebellum)
• enlargement of the posterior fossa (space at the underside of the skull containing the brainstem and cerebellum) with elevated tentorium

Dandy-Walker variant has been characterized as varying degrees of underdevelopment (hypoplasia) of the cerebellar vermis, without enlargement of the fourth ventricle or cisterna magna.

DW malformation and DW variant have many similarities, so a clear-cut distinction on prenatal ultrasound may not always be possible. Furthermore, the exact diagnostic criteria for DW variant are unclear, and some experts suggest the term should no longer be used because it does not seem to be useful for prognosis.

Fetal MRI can be used to better define abnormalities in the fetal brain and to rule out other conditions that may look like a form DW on ultrasound exams. MRI and/or ultrasound after birth can be used to confirm the condition and diagnose any complications affecting the baby. An expert fetal neurological opinion is important because the long-term outcome for conditions that can resemble DW malformation may be much different than in cases of DW malformation.

In a new study published in the American Journal of Medical Genetics, Part A, researchers looked at specific factors that might increase the risk for having a baby with Dandy-Walker malformation (DWM), a rare birth defect that affects the back part of the brain. Researchers looked at many different environmental and lifestyle factors (such as the mother’s and father’s race, mother’s education and age, and certain exposures before and during pregnancy, such as smoking, alcohol use, and infections) and found that most of them were not related to having a baby with DWM. The researchers did identify a few factors that were more common among babies with DWM than among babies without DWM, including black race mothers, twinning, or a history of infertility treatment. The lack of environmental factors suggests that genetic factors might play an important role in DWM. More study of these factors might provide additional clues to the causes of DWM.

You can read an abstract of the article here.

Main Findings

• Researchers found that the following factors were more common among babies with DWM:
  • Mothers that are of black race
  • Twinning
  • History of infertility treatment
• Future studies should further examine the roles of race, twinning, infertility treatment, and genetics in the development of DWM.

About this Study

• Researchers used data on babies that were due to be born between October 1, 1997 and December 31, 2009 from the National Birth Defects Prevention Study (NBDPS). The NBDPS is a population-based, multi-site study, which aims to understand factors related to the risk for major birth defects. Population-based means that researchers look at all babies with birth defects who live in a defined study area, which is important to get a complete picture of what is happening within this known population.
• For this study, researchers looked at factors from one month before pregnancy through the third month of pregnancy.
• Birth defects were identified through birth defects tracking systems in Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, North Carolina, Texas, and Utah.

About Birth Defects

Birth defects are common, costly, and critical conditions that affect 1 in every 33 babies born in the United States each year. Birth defects are structural changes present at birth that can affect almost any part or parts of the body (such as the heart, brain, face, arms, and legs). They may affect how the body looks, works, or both.