Brain scans are used to diagnose hydrocephalus (excess fluid in the brain).

Congenital and acquired hydrocephalus

CT scans and MRI scans are often used in combination to confirm a diagnosis of hydrocephalus present from birth (congenital) and hydrocephalus that develops later in children and adults (acquired).

These scan the brain in detail. They can show the build-up of fluid in the brain and the increased pressure, as well as highlighting any structural defects that may be causing the problem.

Sometimes congenital hydrocephalus is detected before birth, during a pregnancy ultrasound scan.

Normal pressure hydrocephalus

Normal pressure hydrocephalus (NPH) can be difficult to diagnose because the symptoms start gradually and are similar to those of more common conditions, such as Alzheimer's disease.

It's important to make a correct diagnosis because, unlike Alzheimer’s disease, the symptoms of NPH can be relieved with treatment.

Your doctors will assess:

NPH may be diagnosed if you have difficulty walking, mental and bladder problems, and cerebrospinal fluid (CSF) levels that are higher than usual. However, you may not have all these symptoms.

Further tests may also be done to decide whether you would benefit from having surgery, such as a:

Lumbar puncture

A lumbar puncture is a procedure where a sample of CSF is taken from your lower spine. The pressure of the CSF sample is then checked.

Removing some CSF during a lumbar puncture may help improve your symptoms. If it does, you may benefit from having surgery (see treating hydrocephalus to find out more).

Lumbar drainage test

You may have a lumbar drain if a lumbar puncture does not improve your symptoms.

Under local anaesthetic, a tube is inserted between the bones in your spine (vertebra) to drain a large amount of CSF. This is done over a few days, to see whether your symptoms improve.

Lumbar infusion test

During a lumbar infusion test, fluid is slowly injected into the lower part of your spine while measuring the pressure.

Your body should absorb the extra fluid and the pressure should stay low. If your body cannot absorb the extra fluid, the pressure will rise, which could indicate NPH and that surgery will be helpful.

Page last reviewed: 6 February 2023
Next review due: 6 February 2026