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
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
), 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: 5/6/2015
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