Diagnosis of NPH

NPH can present in a similar way to other conditions experienced by older people, and the journey to diagnosis can be long. Read on for more information on how NPH is diagnosed, what other tests you may have, and what other conditions present similarly to NPH. 

 

How is it diagnosed and what other tests may I have?

Imaging

A CT scan of the brain would show the ventricles are larger than expected. Enlarged ventricles are a common finding in older people, as the brain tissue tends to shrink. You may need to have an MRI scan to look in more detail for the cause of the larger ventricles (people with certain metal implants may not be able to have an MRI). The MRI may include an additional scan to look at the blood flow and CSF flow in the brain.

Based on the results of the CT and MRI scans you may then have a consultation with a neurosurgeon. Surgery may be offered at this stage, especially if a disproportionately enlarged subarachnoid space hydrocephalus (DESH) is seen on the scan. This means that there is a larger than expected space below the brain in the skull with a narrowing of the space above the brain, as the brain is pushed upwards by the large amount of CSF. This sign can help identify that a shunt may be beneficial. However, other tests may also be performed first.

 

Lumbar Puncture

One of these further tests may be a lumbar puncture to measure the pressure in the spine, which closely relates to the pressure in the brain. CSF is removed by inserting a needle into the small of the back. Often tests of walking speed and/or cognition are conducted before and after the removal of CSF by lumbar puncture. With NPH, there may be a rapid improvement in symptoms following CSF removal, and this can indicate that symptoms are likely to improve with insertion of a shunt.

Sometimes CSF is drawn slowly from the lumbar spine over 24 or 48 hours, to mimic how a shunt would work, with walking and cognitive tests before and after. This is called Extended Lumbar Drainage (ELD).

An infusion test can also be performed via lumbar puncture, adding a little fluid and measuring how quickly the CSF is absorbed. This can demonstrate an impaired CSF absorption, supporting a diagnosis of NPH.

Watch a video of how a lumbar puncture is performed here.

 

Cognitive tests

You may be referred to a neuropsychologist (a psychologist specialising in the effects of brain function on our thinking and behaviour). Their tests assess memory, language use, speed of thinking, and spatial skills. The assessment will help with diagnosis, since NPH has a distinct pattern of changes, and give a baseline of your cognitive function before treatment.

 

What other conditions could this be?

NPH can present in a similar way to other conditions experienced by older people, for example Alzheimer’s and Parkinson’s diseases. NPH is a potentially reversible cause of dementia and could account for around 6% of people with dementia so it is important to consider NPH as a possible cause of dementia symptoms. Other conditions may also be present as well as NPH. It is possible to have both NPH and Parkinson’s disease, or NPH and vascular dementia at the same time. This can make diagnosis and predicting someone’s improvement after surgery difficult.