Ask the Doctors: Surgical procedure can lessen symptoms of NPH

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Q: What can be done for normal pressure hydrocephalus? My dad was diagnosed with this condition six months ago after developing severe gait problems, urinary urgency and memory issues. He has a few other physical issues, but is otherwise healthy.

A: I'm glad your father's doctor was able to pinpoint the source of his symptoms. Because normal pressure hydrocephalus (NPH) is a rare condition, with a gradual onset of symptoms, it can be difficult to diagnose. The annual incidence is between 1.19 and 3.4 per 100,000 people. This form of hydrocephalus, or "water on the brain," can occur after a head trauma, stroke or brain tumor, but in some cases, the cause is unknown. To understand the condition takes an understanding of the fluid that bathes the entire brain and that flows through its ventricles, or cavities.

This fluid, called cerebrospinal fluid, is produced by the lateral ventricles of the brain and is eventually reabsorbed into the body through veins within the brain. If the body has difficulty reabsorbing the fluid, the fluid increases within the ventricles, putting pressure on the brain itself. This pressure damages the nerves and nerve connections within the brain. Initial symptoms include difficulty walking, as if a person's feet are glued to the floor, and with the feet outwardly rotated. Patients also have difficulty turning and can lose stability and fall.

People with the condition also have concentration problems, slowed mental abilities and a lack of concern for their disability. Lastly, they have urinary urgency, which can lead to urinary incontinence.

Once you have a diagnosis, however, you can move to treatment, which consists of decreasing the level of cerebrospinal fluid within the skull.

This is done through a ventriculoperitoneal (VP) shunt. After drilling a small hole in the skull, a neurosurgeon places a catheter into the lateral ventricle within the brain. That catheter is attached to a valve behind the ear. From the valve, another catheter is guided down the neck and into either the chest or abdomen. When the pressure builds in the ventricle, the valve opens, draining the fluid from the brain into the chest or abdomen, depending where the second catheter ends. This fluid is then reabsorbed by the body.

The effectiveness of shunts varies widely, studies suggest. The greatest patient improvements seem to be in the ability to get up out of a chair and walk. Memory and reaction time also can improve after shunting, as can urinary symptoms. However, if memory deficits are to the point of moderate to severe dementia, then a shunt may not help that aspect.

One important thing to note is that the longer the patient has symptoms, the less likely a shunt will provide benefit. This is especially true if symptoms have been present for more than two years.

VP shunts can have many complications, including a risk of bleeding, brain infections, seizures, malfunction of the shunt or an over-drainage of cerebrospinal fluid. The rates of these complications are decreasing, but still can occur up to a third of the time.

Based on what you've told me, the cause of your father's hydrocephalus is unclear. Nonetheless, if the shunt is stable, patients like your father can have sustained benefit for many years.

Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles. Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.

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