Normal-pressure hydrocephalus is an abnormal increase of fluid in the brain that puts pressure on the brain. It may be caused by a head injury, an infection, a tumour, or by unknown causes.

Normal-pressure hydrocephalus is rare and can be treated. It can occur at any age but is most common in older adults. Symptoms include increased problems with mental abilities such as memory, trouble walking, and problems with bladder control. Because the symptoms are similar to those of other causes of dementia such as Alzheimer's or Parkinson's disease, this condition is often not correctly diagnosed.

If the doctor suspects normal-pressure hydrocephalus, he or she will evaluate how the person walks. Many people with this condition shuffle or walk with their legs wide apart. Tests may include CT scan or MRI, lumbar puncture (spinal tap), ultrasound, and other tests to help rule out other conditions that could be causing the symptoms.

After the doctor has diagnosed normal-pressure hydrocephalus, often a surgeon will place a tube called a shunt. The shunt runs under the skin from the brain to the abdomen. The excess fluid drains through the shunt into the abdomen, where it is reabsorbed by the body. This relieves the pressure in the brain and usually corrects the symptoms.