Congenital Hydrocephalus

How hydrocephalus develops

Cerebrospinal fluid is made constantly inside the ventricles, flows through narrow channels to surround the brain and spinal cord, and is absorbed into the bloodstream. Hydrocephalus happens when this flow is blocked or absorption fails.

• Obstructive (non-communicating): a blockage inside the ventricle system, most often a narrowing of the aqueduct of Sylvius between the third and fourth ventricles.
• Communicating: fluid flows out of the ventricles but is not absorbed properly.

In babies, the skull bones are not yet fused, so the head enlarges as fluid builds up. This can delay, but not prevent, rising pressure on the brain.

Causes of congenital hydrocephalus

• Aqueductal stenosis: narrowing of the channel between ventricles. Some cases are inherited, including an X-linked form (L1CAM gene) affecting boys.
• Spina bifida (myelomeningocele): most babies with this neural tube defect develop hydrocephalus, linked to the Chiari II malformation, in which the lower brain is pulled down into the spinal canal.
• Dandy-Walker malformation: abnormal development of the cerebellum and fourth ventricle.
• Infections during pregnancy: such as toxoplasmosis, cytomegalovirus (CMV), rubella and Zika virus.
• Bleeding in the brain before or around birth, particularly in very premature babies.
• Genetic syndromes and chromosomal conditions.
• Cysts or tumors that block CSF flow (rare).

Taking folic acid before and during early pregnancy reduces the risk of spina bifida and associated hydrocephalus.

Signs and symptoms

Before birth

Enlarged ventricles (ventriculomegaly) are often seen on routine prenatal ultrasound, and fetal MRI gives more detail.

In babies

• a head that is unusually large or growing faster than normal
• a tense or bulging soft spot (fontanelle)
• widened gaps between skull bones and prominent scalp veins
• eyes that look downward ("sunsetting eyes")
• vomiting and poor feeding
• sleepiness or irritability
• seizures
• poor muscle tone or stiff legs
• delayed development

In older children with a shunt

Once the skull bones fuse, raised pressure causes headaches (often worse in the morning), vomiting, blurred or double vision, drowsiness, irritability, declining school performance or personality change.

Diagnosis

• Head circumference measurements plotted on growth charts at every checkup.
• Cranial ultrasound through the soft spot in young babies.
• MRI shows the ventricles, the site of any blockage and associated brain abnormalities.
• CT scan in emergencies.
• Genetic testing and tests for infections when appropriate.
• Eye examination to look for swelling of the optic nerves.

Treatment

Ventriculoperitoneal (VP) shunt

The most common treatment. A thin tube is placed into a ventricle and tunneled under the skin to the abdomen, where the fluid is absorbed. A valve controls the flow. Shunts work well but can block, break, become infected or drain too much or too little. Many children need one or more shunt revisions during their lives.

Endoscopic third ventriculostomy (ETV)

A neurosurgeon uses a small camera to make an opening in the floor of the third ventricle, letting fluid bypass the blockage. It avoids a permanent implant and works best for obstructive causes such as aqueductal stenosis, typically in children older than about 6 months. In infants, ETV is sometimes combined with choroid plexus cauterization (reducing fluid production).

Temporary measures

In premature babies with bleeding, temporary drains or reservoirs may be used until a permanent treatment is possible.

Shunt problems to watch for

Know the signs of shunt malfunction: vomiting, headache, drowsiness, irritability, a bulging soft spot, sunsetting eyes, seizures or loss of skills. Signs of shunt infection, usually within months of surgery, include fever, redness or tenderness along the shunt, and belly pain. Both need emergency care.

Outlook

The outlook depends largely on the cause, any associated brain differences, and how promptly pressure is relieved. Many children with treated hydrocephalus have normal or near-normal intelligence and development. Others have learning difficulties, attention problems, vision problems, epilepsy or physical disabilities, particularly when hydrocephalus comes with other brain conditions or cerebral palsy. With modern care, most children survive into adulthood. Lifelong follow-up with a neurosurgeon is needed.

Support

• early intervention services, physical, occupational and speech therapy
• regular developmental and vision checks
• educational support plans at school
• a written shunt emergency plan for caregivers and teachers

Frequently asked questions

What causes congenital hydrocephalus?

Common causes are narrowing of the brain's fluid channels (aqueductal stenosis), spina bifida with Chiari II malformation, Dandy-Walker malformation, infections in pregnancy such as toxoplasmosis or CMV, bleeding in the brain of premature babies, and genetic conditions.

What are the signs of hydrocephalus in a baby?

Signs include a rapidly growing head, a bulging soft spot, eyes that look downward, vomiting, poor feeding, sleepiness or irritability, and seizures. Regular head measurements at checkups help catch it early.

Can congenital hydrocephalus be cured?

It usually cannot be cured, but it can be effectively treated. A shunt or endoscopic third ventriculostomy controls the fluid buildup and pressure. Most children need lifelong monitoring, and many need shunt revisions over time.

What is the life expectancy with congenital hydrocephalus?

With treatment, most children survive into adulthood and many live a normal lifespan. Outlook depends on the cause, other brain conditions, and quick treatment of shunt problems. Untreated hydrocephalus, by contrast, is often fatal or causes severe disability.