Dandy-Walker malformation

Dandy-Walker malformation, first described by Dr. Walter Dandy and Dr. Arthur Walker, is a congenital brain defect where there’s a cystic malformation in the cerebellum that blocks cerebrospinal fluid from exiting the brain.

This results in increased intracranial pressure and can affect the cerebellum’s ability to control motor skills like walking.

The cerebellum, or "little brain", sits just below the main part of the brain and it’s divided at the midline into two hemispheres by a short worm-like structure called the vermis.

The cerebellum is contained within the back of the skull, in an area known as the posterior fossa, and it sits above the foramen magnum, an opening at the base of the skull through which the spinal cord enters.

The cerebellum controls balance and posture, and helps to initiate as well as fine-tune voluntary motor activity - think about the fancy finger work of a piano player or the vocal cords of a singer - that’s the cerebellum in action.

Now, within the brain there are also four interconnected cavities called ventricles, each of which create and help circulate cerebrospinal fluid.

Highest up, are two C-shaped lateral ventricles that lie deep in each cerebral hemisphere.

The two lateral ventricles drain their cerebrospinal fluid into the third ventricle, which is a narrow, funnel-shaped, cavity at the center of the brain.

The third ventricle makes a bit more cerebrospinal fluid and then sends all of the cerebrospinal fluid to the fourth ventricle via the cerebral aqueduct.

The fourth ventricle is a tent-shaped cavity located between the brainstem and the cerebellum and is continuous with the central canal.

After the fourth ventricle, the cerebrospinal fluid enters the subarachnoid space, which is the space between the two inner linings of the brain - the arachnoid and pia mater.

In a Dandy-Walker malformation, there are three main defects.

First, there’s a cyst in the fourth ventricle which causes the ventricle to enlarge and as a result it presses against the cerebellum, interfering with cerebellar function.