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Normal Pressure Hydrocephalus
Student Health Information Page compiled by: Michael Schneck MD

What is Normal Pressure Hydrocephalus?

This is a disease where there is enlargement of the fluid filled cavities of the brain known as the ventricles (a term referred to as hydrocephalus) without any evidence of rise in measured cerebrospinal fluid (CSF) pressures that may be seen in other forms of hydrocephalus. Another name for NPH is chronic extra ventricular hydrocephalus.

The disease was first well-described by Hakim and Adams in 1965. There are two main types: Primary NPH is the term used when no obvious cause is identified. Secondary NPH is the term used when an identifiable cause is found such as a history of brain tumor, history of bleeding in the brain, previous history of meningitis, or history of head injury among other causes.

Research suggests that NPH may occur from a combination of factors including poor absorption of CSF back into the blood stream or inability of the ventricle to respond normally to other pressure changes in the body.

Features (symptoms or signs) that might lead to the diagnosis of NPH?
This is a chronic disease most typically seen in elderly patients. The three main features of this disease are:

  • Problems with walking often described as a magnetic gait where the patients have trouble lifting their feet and moving smoothly. Patients may say their feet are glued are stuck to the floor
  • Frequent loss of urine (known as urinary incontinence)
  • Problems with thinking and memory (dementia). Typically, the problems with walking and balance appear first and there is a lot of variation in which of the three features presents first as well as the severity and rate at which patients may get worse over time.

With what other diseases might NPH be confused?
NPH is a disease that most commonly occurs in older patients who may have a number of underlying chronic diseases that may cause gait difficulties, dementia, and urinary incontinence. Alzheimer disease and Parkinson disease are among the most well-known degenerative brain diseases that may be confused with NPH. Other chronic diseases that can cause gait problems include arthritis, peripheral neuropathy (damage to the nerves in the arms and legs), dizziness related to inner ear disorders, narrowing of the spine in the neck (cervical) or low back (lumbar) regions. Multiple strokes can also cause dementia, gait difficulty and urinary problem.

How common is NPH and why is this disease important?

The minimum number or frequency of patients with this disease (the ‘prevalence’) of this disease in one study form Norway was 21.9 cases (patients) per 100,000 persons in the population. This frequency increases with age. In the study from Norway, the occurrence of new cases (known as the incidence rate) was at least 5.5 per 100,000 persons per year. The condition occurs mainly in elderly patients and the frequency increases with age. Another report suggested that the prevalence ranges from 3.3 per 100,000 persons age 50 to 59 years. 49.3 per 100,000 persons age 60 to 69 years of age, to 181.7 per 100,000 for persons age 70 to 79. Other studies have suggested incidence rates 0.2 per 100,000 persons per year or 1.8 per 100,000 persons per year.

All of these reports are likely under-estimates of the numbers of patients with NPH because this disease may be poorly recognized. It is thought that NPH may be the underlying cause for 1 of every 20 (5%) of patients with dementia. It is important to recognize NPH because unlike many other chronic forms of dementia or gait difficulty in elderly patients, this is a treatable and possibly reversible condition.

Diagnosis

The clinical history and exam is important. If a patient has progressive gait problems with no other clear cause whether associated with urinary problems or dementia, the diagnosis of NPH may be considered. The preferred test is an MRI of the brain to look at the size of the ventricles though in patients who cannot have an MRI for whatever reason a CT scan may be considered.

If brain imaging shows enlarged ventricles (also known as ventriculomegaly) the next step may be removal of spinal fluid by inserting a needle into the spinal fluid space (typically in the lower back, This procedure is called a large volume lumbar puncture. Improvement in gait after this procedure may suggest that a patient is more likely to get better with subsequent placement of a shunt (see below). (The likelihood of the lumbar puncture predicting improvement, known as positive predictive value, is 73-100%).

Lack of improvement (a negative test) does not rule out the possibility that the patient has NPH, however. A somewhat better test is to drain CSF over several days via a tube known as a lumbar drain. This test requires that the patient be evaluated in a hospital with staff trained to manage these catheters to prevent complications such as infection or spinal injury. Once the diagnosis is thought to be more likely, a shunt is then typically considered.

How is NPH Treated?

Surgical treatment is the therapy of choice for NPH. A shunt is a tube with a built in pressure valve that is inserted into the cerebrospinal fluid (CSF) to drain extra CSF away from the brain thereby allowing enlarged ventricles to decrease. The fluid is ‘shunted’ away from the brain usually into a part of the abdomen known as the peritoneum where the excess CSF is then easily and safely absorbed back into the body.

The most common location is to place this shunt directly into the ventricles and this is known as a ventriculoperitoneal (VP) shunt. Success rates for shunts are variable but when patients are carefully selected, as many as three quarters of patients may show significant improvement

Response to therapy is variable and some patients may improve within a few days or weeks and some patients may take months to improve or at least stabilize and not show further worsening of symptoms. Usually the gait problem tends to improve more than problems with memory and thinking. Shunts are not without risks, however. Among the recognized complications of this procedure are bleeding into the brain, over drainage of CSF and CSF infections.

Which physicians, and other health care providers, diagnose and/or treat NPH?

  • Typically, the diagnosis of NPH is made by neurologists and/or neurosurgeons.
  • Neuropsychologists may help with the diagnosis by analyzing specialized memory tests that help identify problem areas of memory and thinking
  • Neuroradiologists help by analyzing the brain images demonstrating enlarged ventricles
  • Physical therapists and other rehabilitation specialists may also be involved in evaluating problems with walking and mobility
  • If the diagnosis is consistent with NPH, then a shunt (see above) is placed by neurosurgeons.

Resources and Support

Some professional societies, patients associations, and other internet resources that have specific patient information resources available:]

American Academy of Neurology (AAN)
1080 Montreal Avenue
St. Paul, MN 55116-2325
Phone: (612) 695-1940
Fax: (612) 695-2791
www.neurology.org

American Association of Neurological Surgeons (AANS)
22 South Washington Street
Park Ridge, IL 60068-4287
Phone: (847) 692-9500
Fax: (847) 692-2589
Email: info@aans.org
Web: www.neurosurgery.org or www.aans.org

Hydrocephalus Association
Dory Kranz, Executive Director
Pip Marks, OutReach Director
870 Market Street, Suite 705
San Francisco, CA 94102
Phone: (415) 732-7040
Toll-free: (888) 598-3789
Fax: (415) 732-7044
Email: info@hydroassoc.org

National Hydrocephalus Foundation
Debbi Fields, Executive Director
12413 Centralia Rd.
Lakewood, CA 90715-1653
Phone: 562-924-6666
Phone: 888-857-3434
Fax: 562-924-6666
Email: hydrobrat@earthlink.net
Web: www.nhfonline.org

More articles on NPH

  1. Symptomatic occult hydrocephalus with "normal" cerebrospinal-fluid pressure: a treatable syndrome. RD Adams, CM Fisher, S Hakim et al. 1965 New England Journal of Medicine 273: 117–126
  2. Idiopathic normal pressure hydrocephalus: a systematic review of diagnosis and outcome. AO Hebb et al. 2001 Neurosurgery 49: 1166–1184
  3. Development of guidelines for idiopathic normal-pressure hydrocephalus: introduction. Anthony Marmarou A et al. 2005 Neurosurgery 57: S1–S3
  4. The Diagnosis and Treatment of Idiopathic Normal Pressure Hydrocephalus. Gary L Gallia, Daniele Rigamonti, Michael A Williams. Nature Clinical Practice Neurology. 2006; 2(7):375-381.
  5. Prevalence of probable idiopathic normal pressure hydrocephalus in a Norwegian population. A Brean and PK Eide. Acta Neurologica Scandinavica 2008: 118:48-53
  6. Normal Pressure Hydrocephalus. Dalvi A et al. Normal Pressure Hydrocephalus, Medscape, Oct 2010
  7. Normal pressure hydrocephalus: How often does the diagnosis hold water? Bryan T. Lassen and J Eric Alskog. Neurology 2011; 77: 1119

Local Support in Chicaoland Area

Local Chicago area resource for patients seeking an expert physician who can diagnose and/or treat NPH (You can also contact your local hospital for recommendations)

Loyola University Medical Center
Department of Neurology
2160 South First Avenue
Maywood, Illinois 60153
708-216-2662

Loyola University Medical Center
Department of Neurosurgery
2160 South First Avenue
Maywood, Illinois 60153
708-216-3208