MEDICAL SURFARI: WHAT IS NORMAL PRESSURE HYDROCEPHALUS

The human brain has four ventricles (spaces) wherein about a pint of cerebral spinal fluid (CSF) is produced each day. This fluid circulates in and around the brain and spinal cord, bathing it and providing buoyant insulation and protection of these fragile tissues. When an obstruction of the normal flow of CSF occurs, an abnormal buildup might occur, producing a condition called hydrocephalus. This might result in enlargement of the ventricles within the brain and compression of brain tissue, thereby resulting in a poorly functioning brain. The condition of normal pressure hydrocephalus (NPH) is a form of hydrocephalus that has characteristic signs and symptoms quite different than those of hydrocephalus in infants or children or other forms of adult hydrocephalus. I will address those separately in another column.

About one out of 100,000 people develop NPH, and it can occur at any age. However, it typically occurs at senior ages. Most of its effects are essentially reversible when the condition is recognized and properly treated. When this condition occurs, there is an accumulation of CSF, which causes the ventricles of the brain to enlarge but with little or no increase in sustained pressure. The name of this condition is a bit misleading because some patients do show fluctuations in pressure that range from low normal to high. Although hydrocephalus can result from meningitis, brain hemorrhage, brain surgery or tumors in the brain, there is often no medical history that definitely explains the development of NPH.

The symptoms and signs of NPH characteristically include complaints of difficulty walking, mild dementia and urinary incontinence. Patients might demonstrate a wide-based, short, slow and shuffling step that might cause mild imbalance and frequent falls. The problems with gait are often the most pronounced finding and the first to become apparent. With longer standing hydrocephalus, mild dementia in the form of forgetfulness, difficulty dealing with routine tasks and short-term memory loss might occur. The dementia is sometimes also associated with urinary incontinence characterized by urgency and in some cases complete loss of bladder control. Some patients might never develop this sign, but it is often the last apparent symptom.

Treatment by shunting (diverting) the CSF to another part of the body often reverses the effects of hydrocephalus, allowing patients to lead full and active lives. There are many different types of shunting systems that work well, but one of the most advanced systems available is the magnetically programmable valve system manufactured by Johnson & Johnson Professional, Inc. This is the first shunt of its type, and it allows for quick, noninvasive adjustments in valve pressure settings using a small magnet placed over the scalp and shunt. This allows the neurosurgeon to make precision adjustments in the valve pressure to suit the patient's needs as opposed to the patient having to adapt to a shunt with a single fixed valve pressure. This eliminates the need for repeat surgery to replace shunt valves in some patients. This new shunt technology is the result of bringing together experts in neurosurgery, engineering, and interestingly, the watchmaking and micro technology industries as the very tiny precision parts of this shunt were developed and produced in Switzerland.

I have recently used this type of shunt in a few patients here, and I have been very pleased with the results. This is a superior advance in shunt technology that will please patients and clearly improve their quality of living.

NPH is not a hopeless condition; in fact, it is a relatively easily treatable condition. The success rate for shunting can be as high as 80 percent, but left untreated the condition can cause progressive deterioration.

Worldwide Web Resources

Hydrocephalus Association Homepage

neurosurgery.mgh.harvard.edu/ha/

The Hydrocephalus Association Homepage provides educational information on hydrocephalus as well as information on services and resources for patients and families.

The Hydrocephalus Foundation, Inc.

www.hydrocephalus.org/

The Hydrocephalus Foundation provides support, educational resources and networking opportunities to patients and families affected by hydrocephalus.

Dr. Scott Gibbs is a Cape Girardeau neurosurgeon and editor-in-chief of Mosby's Medical Surfari. You may e-mail questions to him at drgibbs@semissourian.com or write in care of the Southeast Missourian, P.O. Box 699, Cape Girardeau, Mo., 63702-0699.