The following information may help to address your question:
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: 6/16/2015
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: 6/16/2015
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: 4/30/2018
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
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: 6/17/2015
How can I find a genetics professional in my area?
Last updated: 12/6/2017
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