Obstructive Hydrocephalus

There are several conditions that can block the normal flow of CSF in the brain, including:

• Aqueduct stenosis – a passage in the brain called the cerebral aqueduct can become too narrow, either from birth or acquired later in life, blocking the passage of fluid.
• Brain tumour – tumours of the posterior fossa (cerebellum, brainstem, fourth ventricle) may obstruct CSF pathways.
• Intraventricular haemorrhage – blood clot within the ventricles blocks CSF flow.
• Meningitis – inflammation and adhesions from meningitis can obstruct CSF pathways.
• Cysts – arachnoid cysts or other intraventricular cysts.

Symptoms are caused by a build-up of pressure in the brain, and they can appear suddenly or develop gradually.

Acute/Subacute Presentation

This is a medical emergency. Symptoms include a severe, worsening headache (often worse in the morning or when lying down), nausea and vomiting, blurred or double vision, drowsiness, and difficulty staying alert. Seek emergency medical attention immediately.

Chronic Presentation

Some people develop symptoms more slowly, over weeks or months. These can include a worsening headache, vision changes, slower thinking, and difficulty walking.

• CT scan – this is usually the first scan done, especially in an emergency. It shows whether the ventricles are enlarged and can help identify where the blockage is and what's causing it. 
• MRI scan – this gives more detailed information about the cause of the blockage and how fluid is flowing through the brain.

Treatment aims to relieve the pressure and restore normal fluid drainage. The right approach depends on the cause and how urgent treatment is required.

External Ventricular Drain (EVD)

If symptoms are severe and rapidly deteriorating, an emergency procedure may be needed to insert a temporary drain into the brain, relieving pressure while the underlying cause is treated.

Endoscopic Third Ventriculostomy (ETV)

For some causes of hydrocephalus, particularly aqueduct stenosis, ETV is an effective treatment. A small endoscope is introduced into the ventricles, and a small opening is made in the floor of the third ventricle, creating a new pathway for CSF to flow directly from the third ventricle to the subarachnoid space, bypassing the obstruction. ETV avoids the need for shunt insertion.

Ventriculoperitoneal (VP) Shunt

A VP shunt provides reliable, long-term CSF drainage for hydrocephalus. This involves placing a thin tube to drain fluid from the brain down to the abdomen, where it's naturally absorbed. Modern shunts have an adjustable valve, so the amount of drainage can be fine-tuned after surgery without further surgery.

Treatment of the Underlying Cause

If the hydrocephalus is caused by something that can be treated directly, such as a tumour or cyst, removing or treating this may resolve the hydrocephalus.