Hydrocephalus

What happens in hydrocephalus

The brain contains four connected cavities called ventricles, filled with CSF. CSF is made continuously (about 500 ml a day in adults), flows through the ventricles, around the brain and spinal cord, and is absorbed into the bloodstream. Hydrocephalus develops when:

• flow is blocked (obstructive or non-communicating hydrocephalus), for example by a narrowed aqueduct or a tumor
• absorption is impaired (communicating hydrocephalus), for example after bleeding or meningitis
• rarely, too much CSF is produced

The ventricles enlarge and press on the surrounding brain.

Types

Symptoms by age

Babies

• an unusually large or rapidly growing head
• a tense or bulging fontanelle (soft spot)
• widely separated skull bones and prominent scalp veins
• downward-gazing eyes ("sunset sign")
• vomiting, poor feeding, irritability, sleepiness
• seizures

Children and adults

• headache, often worse in the morning or when lying down
• nausea and vomiting
• blurred or double vision; swelling of the optic nerves (papilledema)
• drowsiness, irritability, personality changes
• problems with balance, coordination and walking
• declining school or work performance
• bladder control problems

Older adults: normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) classically causes three problems that develop over months:

1. walking difficulty: short, shuffling, "magnetic" steps (gait abnormality)
2. urinary urgency or incontinence
3. memory and thinking problems

NPH is often mistaken for Parkinson's disease or dementia and is one of the few partly reversible causes of these symptoms.

Diagnosis

• head circumference measurements in infants
• prenatal and cranial ultrasound through the fontanelle in babies
• CT scan for rapid assessment, especially in emergencies
• MRI to show the cause and detailed anatomy
• eye exam for papilledema
• for NPH: a lumbar puncture "tap test" or lumbar drain to see whether removing fluid improves walking, plus neuropsychological testing

Treatment

Shunts

A ventriculoperitoneal (VP) shunt is a thin tube that drains CSF from a ventricle under the skin to the abdomen, where it is absorbed. A valve controls the flow, and many valves can be adjusted with a magnet from outside. Other shunt destinations include the heart (ventriculoatrial) or chest cavity.

Shunts work well but often need revision: a significant proportion fail within the first couple of years, and most people with shunts need at least one revision over their lifetime. Complications include:

• shunt malfunction: blockage or disconnection, causing the original symptoms to return
• shunt infection: usually in the first months after surgery
• overdrainage: headaches when upright, or fluid collections around the brain

Endoscopic third ventriculostomy (ETV)

A neurosurgeon uses an endoscope to make a small opening in the floor of the third ventricle, letting CSF bypass a blockage. It avoids a permanent implant and works best for obstructive hydrocephalus in older children and adults. In infants, it is sometimes combined with choroid plexus cauterization to reduce CSF production.

Treating the cause

Removing a tumor or treating infection may resolve hydrocephalus. Temporary external drains are used after bleeding or during infection.

Outlook

With timely treatment, many people with hydrocephalus lead full lives. Outcomes depend on the cause, age at diagnosis and associated brain conditions. Some children have learning difficulties, vision problems, epilepsy or coordination problems and benefit from early intervention, therapies and school support. People with shunts and their families should know the warning signs of shunt failure and have a plan for urgent care.

Frequently asked questions

What are the symptoms of hydrocephalus?

In babies, a rapidly growing head, bulging soft spot, vomiting, sleepiness and downward-looking eyes. In older children and adults, headaches, vomiting, vision problems, drowsiness and balance problems. In older adults, normal pressure hydrocephalus causes walking difficulty, bladder problems and memory loss.

What causes hydrocephalus?

It can be caused by birth defects such as spina bifida or aqueductal stenosis, bleeding in the brain (especially in premature babies), meningitis, brain tumors and head injury. In normal pressure hydrocephalus, the cause is often unknown.

Can hydrocephalus be cured?

Hydrocephalus is usually controlled rather than cured. A shunt or ETV relieves pressure, and treating an underlying cause such as a tumor can sometimes resolve it. Most people need lifelong follow-up.

What are the signs of a shunt malfunction?

Signs are a return of hydrocephalus symptoms: headache, vomiting, sleepiness, irritability, vision changes, seizures and, in babies, a bulging soft spot. Shunt malfunction is an emergency and needs immediate medical care.