Hydrocephalus - Diagnosing hydrocephalus

The different types of hydrocephalus (fluid on the brain) can be diagnosed with brain scans.

Congenital hydrocephalus

In some cases, an ultrasound scan can detect congenital hydrocephalus before your baby is born. An ultrasound scan uses high-frequency sound waves to create an image of your womb and the baby inside.

If your baby has some of the physical characteristics associated with congenital hydrocephalus after they're born, such as an enlarged head, they may be referred for an ultrasound scan. If the results of the ultrasound are inconclusive, further testing can be carried out using:

• a computerised tomography (CT) scan – this takes a series of X-rays at slightly different angles and uses a computer to put the images together
• a magnetic resonance imaging (MRI) scan – this uses a strong magnetic field and radio waves to produce detailed images of the brain

These scans can examine the brain in greater detail. As well as showing the build-up of fluid on the brain and the increased pressure, the scans can also highlight any defects in the structure of the brain that may be causing the hydrocephalus. 

Acquired hydrocephalus

Hydrocephalus that develops in adults or children (acquired hydrocephalus) can be diagnosed using a combination of CT and MRI scans. The scans can also reveal possible causes of your symptoms, such as a brain tumour.

Normal pressure hydrocephalus

Hydrocephalus that usually develops in older people (normal pressure hydrocephalus or NPH) can be difficult to diagnose for the following reasons:

• the symptoms come on very gradually
• the symptoms are more common to conditions, such as Alzheimer's disease, which can frequently occur with NPH

It's important to make a correct diagnosis because, unlike Alzheimer’s disease, it's possible to relieve the symptoms of NPH with treatment.

Healthcare professionals have devised a diagnostic checklist which examines:

• how you walk (your gait)
• your mental ability
• symptoms that affect your bladder control such as urinary incontinence
• the appearance of your brain during CT, MRI and ultrasound scans

You may be diagnosed with NPH if you have the combination of an impaired gait, slowing of the normal mental processes and urinary incontinence, and scans have shown that your cerebrospinal fluid (CSF) is at a higher level than usual.

However, you may not have all of the symptoms on the checklist.

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

• a lumbar puncture
• a lumbar drainage test
• a lumbar infusion test

These procedures are briefly described below.

Lumbar puncture

A lumbar puncture, also known as a spinal tap, is a procedure used to take a sample of CSF from your lower back.

A hollow needle is inserted between your back bones (vertebrae), and a small amount of the fluid is removed. The pressure of the CSF sample can then be checked.

Removing some CSF during a lumbar puncture may help to improve your symptoms. If this is the case, it's a good indication that you may benefit from treatment with surgery (see treating hydrocephalus).

Lumbar drain

If having a lumbar puncture doesn't improve your symptoms, this doesn't mean that you do not have NPH. If the lumbar puncture test is negative, you may have a lumbar drain.

A lumbar drain involves inserting a tube between your back bones to drain a large amount of CSF. This is done over a few days to see if this improves your symptoms, such as your ability to walk around. This is usually done under local anaesthetic to numb the area, or sedation to relax you.

Lumbar infusion test

A lumbar infusion test can also be used to help diagnose NPH and decide whether you need surgery. The procedure should be carried out under local anaesthetic so it shouldn't be painful.

The test involves slowly injecting fluid into your lower back while measuring the pressure. The additional fluid should be absorbed by your body so the pressure stays low. However, if your body can't absorb the extra fluid, the pressure will rise. This could indicate that you have NPH and that surgery will be beneficial.