1b.jpg
2b.jpg
3b.jpg

Recent media attention surrounding the disorder known as "normal-pressure hydrocephalus" (NPH) has stirred ongoing debate about how common it is-or isn't, and how often is it detected-or not. Thinking back to my neurology resident days, the topic of dementia was always emphatically punctuated with the injunction to keep a sharp eye out for NPH-one of the few so-called "reversible" dementias.

Even as we now have two classes of drug treatments that have been demonstrated to slow the progression of clinical symptoms in Alzheimer's disease and other dementias, NPH currently stands as one of the few truly reversible dementias.

What is NPH?

NPH is characterized by three cardinal signs and symptoms: 1) gait disorder, 2) urinary incontinence, and 3) dementia.

The clinical syndrome of NPH typically develops fairly rapidly over a period of a few weeks to several months, most commonly in people over age 60 years. The gait problems are described as a "magnetic" gait, where it appears as if the subject's feet are glued to the floor. Another term used by doctors for this kind of abnormality is "gait apraxia;" patients may say their "legs don't do what they tell them to do."

Urinary incontinence often begins as a sense of urgency and may progress to include bowel incontinence in severe cases.

The dementia of NPH is typically "subcortical" in character, having more to do with general cognitive processes (e.g. slowed down and difficulty processing information) than reflecting specific "cortical" deficits in short-term memory, language, or visual-spatial functioning.

How does NPH cause problems?

The pathophysiology of NPH is not completely understood, but the term "normal" pressure is probably misleading. By way of analogy, think of a sink that is completely enclosed (like the brain within the head) with a faucet and a drain. Cerebrospinal fluid (CSF) is fluid that comes out a "faucet" within the inner surface of the brain (ventricles) and circulates around the brain and spinal cord to provide cushion and nutrition.

Around the top of the brain is a mesh-like lining called the "meninges." Within this lining are granules that allow some of the CSF to trickle out and be recycled. If these granules get clogged (like a drain), pressure will build up inside the ventricles and cause them to enlarge.

To some degree the brain can be compressed to accommodate this increased pressure, but eventually the pressure build-up can overwhelm the brain's ability to be "squished."

The part of the brain most vulnerable to this pressure build-up is in the middle of the frontal lobes, which controls the legs, bladder, and general cognitive information processing.

How is NPH diagnosed?

Although the diagnosis of NPH rests largely on clinical grounds, recent technological advances are improving our ability to make the diagnosis and assess prognosis for treatment. An MRI brain scan in someone with NPH typically shows very large ventricles deep within the brain but relatively normal appearing cortical (outer) surfaces. This is distinct from Alzheimer's and other degenerative disorders, where enlarged ventricles may occur in conjunction with tissue loss or atrophy in the cortical regions, as well.

Sometimes a cisternogram is ordered, which involves a spinal tap in the lower back and injection of a radioactive tracer into the CSF circulation. The test is performed by repeated scanning every day to see how much of the tracer is taken up into the brain over a 2-3 day period.

Special MRI imaging tests are now available at specialized centers to measure CSF flow through the ventricles, which can more readily help confirm the diagnosis. Perhaps the most important part of a diagnostic evaluation is to perform a spinal tap to withdraw enough CSF to lower the pressure build-up and see if there is clinical improvement.

If initial results are unclear, this procedure may be repeated several times or a drain may be placed for a few days to more consistently lower the CSF pressure.

How is NPH treated?

If the clinical symptoms associated with NPH improve with a spinal tap, this suggests a good prognosis for placing a shunt to divert excess CSF from the brain ventricles down into the abdominal cavity.

 

This procedure, which is performed by a neurosurgeon, is not a major procedure by neurosurgical standards, but still carries the risk of infection or bleeding. Any decision about evaluating or treating possible NPH needs to take into account individual factors, including age and other medical conditions.

What factors affect prognosis?

By far the most important determinant of clinical response to shunting in NPH is duration of symptoms. In general, symptoms that have persisted for more than about a year do not improve as much with a shunt than symptoms of lesser duration. So, time is of the essence in seeking an evaluation.

If you or someone you know is displaying symptoms described, please see a neurologist or call (919) 966-8168 to schedule an appointment at the UNC Memory & Cognitive Disorders Clinic.

About Us

AlzNC Walk Logo
Alzheimers NC Walks

Join our communities across North Carolina and help us continue supporting families dealing with Alzheimer's or other dementias. Register to walk.

Candlelight
Reflections

Join AlzNC for its annual Candlelight Ceremony Thursday, November 6, 2014. 6:30 p.m. NC State Fairgrounds - Waterfall at Dorton Arena

Guardian Angel

A 501(C)3 non-profit supporting local Alzheimer's research and Alzheimers North Carolina, Inc.

Donations needed and appreciated.
Tax receipt available.

Visit the Guardian Angel Site
742 N. Main Street
Fuquay-Varina, NC 27526
919.567.8152