Normal pressure hydrocephalus (NPH) is a form of hydrocephalus , also known as "water on the brain," which means there is too much fluid pressing on the brain.

NPH can occur without a known cause, or it may be caused by any condition that blocks the flow of cerebrospinal fluid (CSF). The fluid-filled chambers (ventricles) of the brain enlarge to fit the increased volume of CSF. They press down on and damage or destroy brain tissue.

Risk factors include:

• Bleeding from a blood vessel or aneurysm in the brain (subarachnoid hemorrhage )
• Closed head injury
• Meningitis or similar infections
• Surgery on the brain (craniotomy )

The CSF is produced in normal amounts in these conditions, but it is prevented from being reabsorbed normally.

NPH is thought to account for about 5% of all dementias .

The symptoms often begin slowly.

Early symptoms include:

• Changes in gait , including inability to begin walking (gait apraxia )
• Sudden fall without loss of consciousness or other symptoms (drop attacks)
• Unsteady walking
• Weakness of the legs

Symptoms as the disorder gets worse:

• Apathy
• Dementia
• Difficulty paying attention
• Impaired memory
• Less spontaneous behavior
• No mood (flat affect)
• Speech impairment
• Urinary or bowel incontinence
• Withdrawn behavior

An examination shows walking (gait) changes related to the damage in the brain. Deep tendon reflexes may be increased in the lower legs.

Tests include:

• Lumbar puncture (spinal tap)
• Head CT scan or MRI of the head
• RHISA scan

The goal of treatment is to improve symptoms. The treatment of choice is surgery to place a tube called a shunt that routes the excess CSF out of the brain ventricles.

Treatment may vary depending on the symptoms and how much the therapy relieves them.

If there is a known cause and the cause can be corrected, the symptoms may be reversed or at least stopped from getting worse. Without treatment, symptoms often get worse and could lead to death.

Surgical treatment improves symptoms in about 50% of cases. People with minimal symptoms have the best outcome. Other people may have different degrees of disability.

• Complications of surgery (infection, bleeding)
• Dementia
• Injury from falls
• Shortened life span
• Side effects of medications
• Temporary or permanent loss of brain functions

Call your health care provider if you have symptoms of normal pressure hydrocephalus.

Call your health care provider if a person with NPH worsens to the point where you are unable to care for the person yourself.

Go to the emergency room or call the local emergency number (such as 911) if a sudden change in mental status occurs. This may mean that another disorder has developed.

Treating disorders that lead to NPH may prevent it in some cases. It may not be preventable in other cases, but early treatment may prevent severe symptoms.

Goetz CG. Goetz: Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa: Saunders; 2007.