Normal pressure hydrocephalus is a reversible cause of dementia seen in elderly patients. It is thought to be secondary to reduced CSF absorption at the arachnoid villi. These changes may be secondary to head injury, subarachnoid haemorrhage or meningitis.


  • Incidence: 6.00 cases per 100,000 person-years
  • Peak incidence: 60-70 years
  • Sex ratio: 1:1
Condition Relative
Normal pressure hydrocephalus1
Multiple system atrophy0.10
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Clinical features

A classical triad of features is seen
  • urinary incontinence
  • dementia and bradyphrenia
  • gait abnormality (may be similar to Parkinson's disease)

It is thought around 60% of patients will have all 3 features at the time of diagnosis. Symptoms typically develop over a few months.


  • hydrocephalus with an enlarged fourth ventricle
  • in addition to the ventriculomegaly there is typically an absence of substantial sulcal atrophy


  • ventriculoperitoneal shunting
  • around 10% of patients who have shunts experience significant complications such as seizures, infection and intracerebral haemorrhages