Obstructive Hydrocephalus

How CSF normally flows

The brain makes about 500 ml of CSF a day, mainly in the choroid plexus within the ventricles. CSF flows from the two lateral ventricles to the third ventricle, through a narrow channel called the cerebral aqueduct to the fourth ventricle, then out into the spaces around the brain and spinal cord, where it is absorbed into the bloodstream.

In obstructive (non-communicating) hydrocephalus, the blockage is inside this ventricular system, so the ventricles upstream of the block enlarge. In communicating hydrocephalus, fluid flows through the ventricles normally but is not absorbed properly. See hydrocephalus for the overview of all types.

Causes

Symptoms

Babies

• rapidly increasing head size
• bulging, tense soft spot (fontanelle)
• widely separated skull bones
• vomiting and poor feeding
• irritability or sleepiness
• downward gaze ("sunsetting eyes")
• seizures

Older children and adults

• headache, often worse in the morning or when lying down
• nausea and vomiting
• blurred or double vision, swelling of the optic nerve (papilledema)
• drowsiness and confusion
• balance problems, clumsiness
• urinary incontinence
• changes in personality or school or work performance

Rapid blockage, for example from a tumor or bleed, can cause fast deterioration and is an emergency.

Diagnosis

• MRI is the best test: it shows enlarged ventricles, the site of the blockage and its cause. Special flow-sensitive sequences show whether CSF moves through the aqueduct.
• CT scan for rapid assessment in emergencies.
• Cranial ultrasound through the fontanelle in infants.
• Prenatal ultrasound can detect hydrocephalus before birth.
• Eye exam for papilledema.
• Lumbar puncture is avoided in obstructive hydrocephalus because of the risk of brain herniation.

Treatment

Emergency treatment

An external ventricular drain (a temporary tube from the ventricle to a collection bag) relieves pressure quickly in acute cases.

Endoscopic third ventriculostomy (ETV)

A neurosurgeon uses an endoscope to make a small opening in the floor of the third ventricle, letting CSF bypass the blockage and flow to the absorption sites. It avoids implanted hardware. It works best for aqueductal stenosis and obstruction from tumors, and in children over 1 year and adults. In infants, it is sometimes combined with choroid plexus cauterization (ETV/CPC).

Shunt

A ventriculoperitoneal (VP) shunt is a thin tube with a valve that drains CSF from the ventricle to the abdomen, where it is absorbed. Other routes include the heart (VA shunt) or chest lining. Shunts are effective but can block, become infected or need adjustment; many people need at least one revision over their lifetime.

Treating the cause

Removing a tumor or cyst can restore normal flow and sometimes avoid a permanent shunt.

Complications

• shunt malfunction or infection
• vision loss from prolonged pressure
• developmental delay and learning difficulties
• epilepsy
• brain herniation in severe, untreated cases

Outlook

With timely treatment, many people with obstructive hydrocephalus live full lives. Outcomes depend on the cause, how quickly treatment was started, and other associated conditions. Children may need developmental support, and lifelong awareness of shunt malfunction symptoms is essential.

Frequently asked questions

What is obstructive hydrocephalus?

It is a buildup of cerebrospinal fluid in the brain's ventricles caused by a blockage inside the brain's fluid pathways, such as a narrowed aqueduct or a tumor. The trapped fluid enlarges the ventricles and raises pressure inside the skull.

What is the difference between obstructive and communicating hydrocephalus?

In obstructive hydrocephalus, fluid is blocked within the ventricles. In communicating hydrocephalus, fluid flows freely through the ventricles but is not absorbed properly, often after bleeding or meningitis. The distinction guides treatment: ETV works mainly for obstructive types.

Can obstructive hydrocephalus be cured?

If the blockage can be removed, such as a tumor or cyst, normal flow may return. Otherwise, ETV or a shunt controls the condition long term. Many people do very well, though shunts may need revisions over time.

What are the signs of shunt failure?

Signs include headache, vomiting, sleepiness, irritability, vision problems, and in babies a bulging soft spot or increasing head size. Fever or redness along the shunt suggests infection. Shunt failure is an emergency and needs immediate medical care.