Dandy-Walker complex

What causes Dandy-Walker complex?

In most cases, the exact cause of Dandy-Walker complex is unknown. It is thought that most cases are caused by a combination of genetic and environmental factors that affect early development before birth. In some cases, exposures that occur during pregnancy, such as a pregnant woman having diabetes or an infection such as rubella, are thought to cause an increased risk for the developing baby to have Dandy-Walker complex.

In some cases, Dandy-Walker complex is caused by an underlying genetic change. For example, some people with Dandy-Walker complex have extra or missing pieces of chromosomes in each cell of the body (chromosome abnormalities). Dandy-Walker complex can also occur as a symptom of another genetic syndrome. For example, people with Dandy-Walker complex may have a change in a gene that causes them to develop Dandy-Walker complex as well as other health problems. Researchers are currently learning more about genes in which changes (pathogenic variants or mutations) can cause Dandy-Walker complex.

Last updated on 05-01-20

How is Dandy-Walker complex diagnosed?

Dandy-Walker complex may be suspected when a doctor observes signs and symptoms of the complex including an increased head size and developmental delay. A doctor may order tests to evaluate the cause of these symptoms, including imaging of the brain. Most typically, a brain ultrasound, CT scan, or brain MRI is used to diagnose Dandy-Walker complex. In some cases, the doctor may order genetic testing to determine if there is an underlying genetic cause for the complex.

Last updated on 05-01-20

Is Dandy-Walker complex inherited?

Most cases of Dandy-Walker complex are sporadic, meaning they occur in people with no history of the complex in their family. The cause of most cases of Dandy-Walker complex remains unknown. A small percentage of people with Dandy- Walker complex may have other family members with the complex, but it is not clear how the complex is inherited. When the complex is not thought to be caused by a single genetic change (pathogenic variant or mutation), the risk for a sibling to have the complex is between 1-5%.

When Dandy-Walker complex is caused by an underlying genetic syndrome, the chance for family members to have the complex as well depends on the inheritance pattern of the underlying syndrome.

Last updated on 05-01-20

When does the cerebellar vermis develop in a fetus, and when can a problem be diagnosed?

The development of the cerebellar vermis begins during the 9th week of gestation, and the entire vermis and cerebellum may be fully formed by the end of the 15th week of gestation. Some experts have noted that it may be fully formed by the end of 16 weeks gestation. However, while Dandy-Walker malformation (DWM) has been diagnosed in the first trimester, a false-positive diagnosis can be made at gestational ages of less than 18 weeks. Experts have noted that prenatal diagnosis of cerebellar malformations, particularly subtle findings such as Dandy-Walker variant, should not be made at less than 18 weeks gestation because it is possible that the development of the cerebellar vermis is incomplete. Even after 18 weeks gestation, there are limitations in defining the presence or extent of defects in the cerebellum and/or vermis. The diagnostic criteria for Dandy-Walker variant remain unclear, and the diagnosis does not appear to predict the final outcome.

Last updated on 05-01-20

What testing is available for a fetus who may have Dandy-Walker variant?

Prenatal diagnosis for a fetus suspected of having a form of Dandy-Walker complex can be challenging. Prenatal ultrasounds and invasive genetic testing via amniocentesis or chorionic villus sampling have the ability to identify non-CNS anomalies and chromosome abnormalities. However, the accuracy of ultrasound in detecting all forms of Dandy-Walker complex and more subtle CNS anomalies is less known. There remains a discrepancy between prenatal ultrasound and postnatal diagnosis in Dandy-Walker variant. Postnatal imaging is generally used to confirm the diagnosis.

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 of Dandy-Walker 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 a Dandy-Walker malformation may be much different than in cases of Dandy-Walker malformation.

People with specific questions about prenatal imaging and testing for a form of Dandy-Walker complex should speak with a fetal neurologist and/or a genetics professional who specializes in prenatal care.

Last updated on 05-01-20

What is the difference between Dandy-Walker malformation and Dandy-Walker variant?

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.

Last updated on 05-01-20

Can both Dandy-Walker malformation and Dandy-Walker variant be associated with other abnormalities?

Yes, both Dandy-Walker (DW) malformation and DW variant can be associated with central nervous system (CNS) malformations, non-CNS malformations, extra or missing chromosomes (aneuploidy), and poor neurological outcome. Because of this, some experts feel there is no role in differentiating the two. While many have tried to distinguish between the two to better define the prognosis for an affected fetus, it is unclear how useful this is in clinical practice.

DW malformation has been known to occur in single-gene disorders (those caused by mutations in a single gene), chromosome abnormalities, environmentally-induced syndromes, or with other abnormalities. In one series of 50 cases of DW malformation and 49 cases of DW variant, the incidence of additional CNS and non-CNS anomalies, and the incidence of chromosome abnormalities, were similar in both groups. In a different study of 17 cases of only DW variant, 4 fetuses had ventriculomegaly and 3 had agenesis of the corpus callosum. Almost half of the affected fetuses had other non-CNS abnormalities, including congenital heart defects, gastrointestinal malformations, renal (kidney) malformations, and intrahepatic (liver) calcifications. However, another study of 19 cases of DW variant (diagnosed strictly as isolated inferior vermian hypoplasia by fetal MRI) found near-normal outcome. This would indicate the importance of using strict criteria for prenatal diagnosis.

If a diagnosis of DW malformation or DW variant is suspected in a fetus, a fetal MRI and consultation with an expert in fetal neurology is recommended.

Last updated on 05-01-20

How successful is a shunt in treating adults with Dandy-Walker variant?

We are not aware of information in the medical literature that describes the long-term outlook after shunt insertion in adults with Dandy-Walker variant specifically. Each person's prognosis varies based on a number of factors including the severity of the defect, whether associated abnormalities are present, and whether complications arise.

According to a 2006 article about treatment options for Dandy-Walker malformation, shunt use has considerably reduced mortality and morbidity rates compared with the open surgical procedures that have been in practice in the past few decades. However, frequent device malfunction and permanent shunt dependency have been a constant problem with shunt insertion.

People with questions about specific prognosis information for themselves or family members should speak with their health care provider.

Last updated on 05-01-20

What is the long-term outlook for people with Dandy-Walker complex?

The long-term outlook for people with Dandy-Walker complex depends on the symptoms that are caused by the changes in the structures of the brain. The long-term outlook also depends on whether Dandy-Walker complex occurs alone (isolated) or whether there is an underlying genetic syndrome that may cause other health problems. Because the differences in brain structure and the presence of an underlying genetic syndrome may affect the signs and symptoms or life expectancy that a person has, it may be difficult to predict the long- term outlook for people who have Dandy-Walker complex.

Some people with Dandy-Walker complex may have physical disabilities or intellectual disabilities. In most cases, infants who have isolated Dandy-Walker variant are more likely to have normal outcomes in the newborn period.

Last updated on 05-01-20

How might Dandy-Walker complex be treated?

Treatment for Dandy-Walker complex is focused on relieving any pressure on the brain that is caused by the brain malformations. If there is excess fluid in the brain, a doctor may perform a surgery to place a ventriculoperitoneal shunt in the brain, which allows for the excess fluid to be drained. This can relieve the pressure in the brain and reduce some symptoms of Dandy-Walker complex. Medications can be used to help control seizures. Other symptoms of Dandy-Walker complex such as developmental delay or trouble coordinating movements may be treated with occupational therapy or physical therapy. Some children with Dandy-Walker complex may require additional help in school such as special education classes.

Last updated on 05-01-20

Name: Dandy-Walker Alliance, Inc. 10325 Kensington Pkwy. Suite 384
Kensington, MD, 20895, United States
Toll Free: 877-Dandy-Walker (326-3992) Email: comments@dandy-walker.org Url: http://www.dandy-walker.org
Name: Hydrocephalus Association 4340 East West Highway Suite 905
Bethesda, MD, 20814, United States
Phone: +1-301-202-3811 Toll Free: 1-888-598-3789 Fax : +1-301-202-3813 Email: info@hydroassoc.org Url: https://www.hydroassoc.org/
Name: Hydrocephalus Canada 16 Four Seasons Place Suite 111
Toronto, M9B 6E5, Canada
Phone: 416-214-1056 Toll Free: 800-387-1575 Fax : 416-214-1446 Email: provincial@sbhao.on.ca Url: http://www.hydrocephalus.ca
Name: Pediatric Hydrocephalus Foundation, Inc, 10 Main Street Suite 335
Woodbridge, NJ, 07095, United States
Phone: (732) 634-1283 Fax : (847) 589-1250 Email: kim@hydrocephaluskids.org Url: http://www.hydrocephaluskids.org/

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