Dandy-Walker Syndrome

What happens in Dandy-Walker syndrome

The cerebellum controls balance and coordination. In Dandy-Walker malformation, three features occur together:

1. Absent or underdeveloped cerebellar vermis, the strip joining the two halves of the cerebellum
2. Cyst-like enlargement of the fourth ventricle
3. Enlarged posterior fossa, the space at the back of the skull

This can block the flow of cerebrospinal fluid, causing hydrocephalus in the majority of children, often in the first year of life.

Causes

The malformation develops early in pregnancy. Known contributors include:

• chromosomal conditions (for example trisomies 13, 18 and 9)
• single-gene syndromes
• prenatal exposures such as infections (rubella, cytomegalovirus) and maternal diabetes or alcohol, in some cases

In many children, no cause is found. Genetic testing helps identify causes and guide family planning.

Signs and symptoms

In babies:

• rapidly increasing head size, a bulging soft spot, and prominent scalp veins
• irritability, vomiting and feeding problems
• jerky eye movements

In older children:

• delayed motor milestones such as sitting and walking
• poor balance, unsteady walking and clumsiness (ataxia)
• muscle stiffness or low muscle tone
• learning difficulties or intellectual disability in some
• seizures in a minority
• headaches and vomiting if pressure rises

Many children also have other differences, such as heart defects, cleft palate, abnormalities of the corpus callosum, or kidney anomalies.

Diagnosis

• Prenatal ultrasound, usually at the anatomy scan around 18 to 22 weeks, may show an enlarged posterior fossa. Findings are confirmed with fetal MRI, since milder variants (such as a mega cisterna magna) can look similar early in pregnancy.
• MRI after birth confirms the diagnosis and shows associated brain differences.
• Genetic testing: chromosome microarray and other tests.
• Heart, kidney and eye evaluations to look for associated problems.

Treatment

There is no treatment to change the malformation itself. Care focuses on:

• Hydrocephalus: a ventriculoperitoneal shunt drains excess fluid to the abdomen. Sometimes a shunt is placed directly into the cyst, or an endoscopic third ventriculostomy creates a new drainage path.
• Physical, occupational and speech therapy for motor and communication skills.
• Developmental and educational support, including early intervention programs.
• Seizure management with anti-seizure medicines.
• Treatment of associated conditions, such as heart defects.
• Regular neurosurgical follow-up, because shunts can block or become infected.

Outlook

Outcome varies a great deal. Children whose malformation occurs alone, without other brain or genetic abnormalities, often have normal or near-normal intelligence and mainly motor delays. Those with additional brain malformations or genetic syndromes are more likely to have significant developmental disability. Prompt treatment of hydrocephalus is important for the best outcome.

Frequently asked questions

What is Dandy-Walker syndrome?

It is a rare congenital brain malformation in which the middle part of the cerebellum is underdeveloped and a fluid-filled cyst forms at the back of the brain. It often causes hydrocephalus and can affect balance, coordination and development.

Can Dandy-Walker be detected before birth?

Yes. It can often be seen on the second-trimester anatomy ultrasound and confirmed with fetal MRI. Genetic testing during pregnancy may identify a cause and help predict the outlook.

What is the life expectancy for Dandy-Walker syndrome?

Many children with isolated Dandy-Walker malformation live into adulthood with good quality of life. Life expectancy is reduced mainly when there are severe associated brain, heart or genetic conditions, or complications of hydrocephalus.

Do all children with Dandy-Walker need a shunt?

No. Many do, because hydrocephalus is common, but some children never develop raised pressure and need only monitoring. Doctors follow head growth and imaging closely, especially in the first year.