Dandy-Walker malformation

Definitions & Key takeaways

Dandy-Walker malformation (DWM) is a congenital brain defect in which the 4th ventricle fails to close. It is characterized with a cysts in the 4th ventricle, hypoplasia of the cerebellar vermis, and enlargement of the posterior cranial fossa. This condition results in hydrocephalus, increased intracranial pressure, and a characteristic "dandy walker" appearance on neuroimaging.

Symptoms of DWM vary depending on the degree of cerebellar hypoplasia. Patients may experience delayed milestones, hypotonia, ataxia, vomiting, and seizures. Hydrocephalus can cause enlargement of the head (macrocephaly) and bulging fontanelles.

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Introduction0:00–0:24

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.

Physiology0:24–1:57

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 medulla oblongata 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.

Pathology1:57–2:54

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.
Secondly, the posterior fossa space is usually enlarged. Thirdly, the cerebellar vermis which divides the cerebellum into its hemispheres is either smaller than normal or absent altogether.
Although the mechanism is not well understood, these features block the normal flow of cerebrospinal fluid from the fourth ventricle into the subarachnoid space.
Since the cerebrospinal fluid can’t flow out of the fourth ventricle, it builds up in the ventricles and makes them expand, which results in hydrocephalus, or the buildup of fluid within the brain.
Hydrocephalus leads to an increase in intracranial pressure as well as an enlarged head circumference or macrocephaly. The symptoms of Dandy-Walker malformation typically start at birth or soon after birth, and they include irritability, vomiting, and seizures.

Symptoms2:54–3:21

Over time, infants may have delays in motor skills such as crawling and walking, and the cerebellar dysfunction can lead to movement symptoms like an unsteady gait or ataxia, abnormal eye movements, muscle paralysis or spasticity, and abnormal breathing patterns.

Diagnosis and treatment3:21–3:54

Dandy-Walker malformation is often diagnosed prenatally via ultrasound, and can be confirmed with a brain MRI. Treatment for Dandy-Walker malformation typically involves the placement of a shunt, like a ventriculoperitoneal shunt, which connects the ventricular system to the peritoneal cavity in order to allow fluid to drain out and get reabsorbed by the cells lining the peritoneal pleura.
This helps to reduce the intracranial pressure caused by hydrocephalus. In addition, individuals often benefit from physiotherapy to help them develop their motor skills.

Review3:54–4:17

All right, as a quick recap...Dandy-Walker malformation is a congenital disorder characterized by three features: a cyst that dilates the fourth ventricle, enlargement of the posterior fossa, and an absence of the cerebellar vermis.
Symptoms include movement abnormalities and hydrocephalus, and it is commonly treated with a ventriculoperitoneal shunt.