Dandy-Walker Malformation Health Article

Definition

Dandy-Walker malformation is a congenital (present at birth) condition involving several abnormalities in the development of the brain. The malformation appears to result from destructive processes, such as inflammation or trauma, which block the circulation of cerebrospinal fluid (CSF) inside the head after the brain has been formed in the embryo.

Description

Dandy-Walker malformation was first described in 1914 by Drs. Dandy and Blackfan. The disorder typically includes the following abnormalities in brain structure:

• Absence or incomplete formation of the vermis, the middle portion of the cerebellum, which is the part of the human brain that lies behind the two cerebral hemispheres.
• Enlargement of the fourth ventricle, one of the human brain's four interconnected ventricles (inner cavities or chambers) that produce cerebrospinal fluid (CSF). In Dandy-Walker malformation, the CSF cannot circulate freely through the ventricles and the rest of the central nervous system (CNS), so it builds up inside the fourth ventricle and causes it to enlarge.
• Cysts (sacs) containing CSF are formed in the posterior fossa, which is a hollow at the back of the skull that covers the cerebellum.
• Absence or incomplete formation of the three foramina (small openings or holes) in the fourth ventricle.

In Dandy-Walker malformation, the CSF produced by the ventricles of the brain is not fully reabsorbed by the body; thus, the excess fluid accumulates in the fourth ventricle and the posterior fossa. As cysts in these areas grow, pressure from the fluid rises, producing a condition known as obstructive, or non-communicating, hydrocephalus (excess fluid on the brain). This type of hydrocephalus develops in 90% of children diagnosed with Dandy-Walker malformation. The size of the head may or may not be affected by the fluid pressure.

Genetic profile

The genetic transmission of Dandy-Walker malformation is not fully understood because the disorder often occurs with other birth abnormalities including cleft palate, extra fingers (polydactyly) or fingers joined together (syndactyly), cataracts, and malformations of the face or heart. An abnormality in the central nervous system that often occurs together with Dandy-Walker malformation is agenesis (absence or failure to develop) of the corpus callosum, the thick band of nerve fibers that joins the two cerebral hemispheres. It is not yet clear whether these and other abnormalities in CNS development are determined by the same gene or whether they are inherited separately.

Dandy-Walker malformation appears to be transmitted in some families in an autosomal, or X-linked, recessive pattern, which means that both parents have one copy of the changed (mutated) gene but do not have the malformation. These families have a high risk of recurrence of the malformation. Families in which there has been inbreeding among close relatives also appear to transmit Dandy-Walker in an autosomal recessive pattern. Several chromosomal abnormalities have been associated with Dandy-Walker.