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Normal Pressure Hydrocephalus (NPH):
New Guidelines for Diagnosis and Treatment

Up to 10 percent of those diagnosed with dementia are believed to actually have a condition called normal pressure hydrocephalus (NPH).(i) Of the estimated 750,000 Americans suffering from NPH, fewer than 20 percent are appropriately diagnosed and treated.(ii) Often mistaken for Alzheimer’s disease, Parkinson’s disease, or merely accepted as part of the aging process, NPH—though it generates similar symptoms—is unique in that it is treatable.

“Because the symptoms can be confusing, many patients never get referred to a neurosurgeon, so normal pressure hydrocephalus often goes undetected and untreated,” says Lorenzo Muñoz, M.D., CINN neurosurgeon and Director of the NPH program at Rush University Medical Center. The all-too-few NPH patients who do receive an accurate diagnosis and are treated accordingly, can in most cases go on to live normal, active lives. Already in practice at CINN, an innovative set of new guidelines for distinguishing and treating the condition promises to increase that number rapidly.

Normal pressure hydrocephalus is an accumulation of cerebrospinal fluid (CSF) that enlarges the ventricles in the brain, sometimes with little or no increase in intracranial pressure (ICP), and is treatable through shunting.iii The condition has traditionally been recognizable through a triad of clinical progressive symptoms: gait disturbance, urinary incontinence and mild dementia. However, even if such symptoms exist in a patient, there is a great difficulty in determining whether that patient is an appropriate candidate for a shunt; until just recently, no single diagnostic study had emerged as highly reliable.iv This past June in Chicago, Anthony Marmarou, Ph.D., internationally renowned NPH researcher and vice chairman of the Division of Neurosurgery at Virginia Commonwealth University in Richmond, reported on the results and corresponding new NPH guidelines that have developed from his recent spearheading of the most comprehensive NPH study to date. Marmarou and his four member NPH advisory board reported an astounding and unprecedented 89.3% accuracy rate in correctly predicting shunt outcomes by way of the new guidelines.(v)

Guidelines for Diagnosis

Post-shunt ê Marginal reduction in ventricle size. Pressure setting is managed in small increments to optimize clinical results.
Pre-Shunt — Enlarged ventricle, one indication of possible Normal Pressure Hydrocephalus (NPH)

Marmarou’s guidelines are designed specifically to diagnose and treat primary (or idiopathic) normal pressure hydrocephalus (iNPH), simply being a case of NPH that has no known cause. The majority of NPH cases fall into this category; however, at times a case of NPH can be identified as a reaction to a known event and is therefore referred to as secondary NPH (sNPH).vii Secondary NPH may develop as the result of a head injury, cranial surgery, subarachnoid hemorrhage, tumor or cysts, subdural hematomas, bleeding during surgery, meningitis or other brain infections.(viii)

To correctly diagnose a patient displaying symptoms of iNPH, primary care doctors, neurosurgeons and neurologists must pool together evidence derived from the patient’s clinical history, a neurologic examination, brain imaging and cerebrospinal fluid pressure measurement. The clinical history should indicate the presence of an adult-onset disturbance of gait, balance, cognition and/or urinary continence that has no identifiable antecedent cause. Structural brain imaging, preferably MRI or CT, should confirm the presence of non-obstructive ventricular enlargement (Evan’s Index >=0.3). Spinal MRI and Spectroscopy may also be used as part of the radiologic workup.(ix)

If iNPH is thus suspected, further clinical and laboratory tests may be carried out in an attempt to increase confidence in the diagnosis and identify other possible causes for the symptoms. Marmarou notes that a positive response to CSF drainage is not unique to iNPH and therefore should not be used alone as convicting evidence; likewise, a lack of improvement after drainage should not exclude an iNPH diagnosis. Because of such nuances in diagnosis, Marmarou urges physicians to classify patients into “Probable,” “Possible” and “Unlikely” categories as appropriate based on the confidence level of the diagnosis in individual cases. Probable and Possible iNPH cases may or may not prove to be shunt responsive. In this manner, shunt responsiveness should be viewed as a measure of treatment outcome as opposed to a criterion for iNPH diagnosis.(x)

Probable(xi)

Probable iNPH patients should have a history including all of the following five criteria:

  1. NPH symptoms are insidious in onset (versus acute)
  2. Symptoms take origin after age 40
  3. Symptoms have a duration of no less than three months
  4. Symptoms are not attributable to other documented neurologic, psychiatric or general medical conditions
  5. Symptoms are progressive

Gait disturbance is a mandatory symptom for patients to be categorized as Probable. In addition, an impairment of either urinary function or cognition must be present. All three classic symptoms need not be present.

Gait disturbance may manifest itself in a variety of ways. At least two of the following signs of gait must be observed for Probable classification: Decreased step height; decreased step length; decreased cadence/speed of stride; increased trunk sway during ambulation; widened standing base; toes turned outward on ambulation; spontaneous or provoked retropulsion; en bloc turning (requiring three or more steps for a 180 degree turn).

Urinary impairment in the iNPH context should include one of the following symptoms not attributable to primary urologic disorders or other causes: episodic or persistent urinary incontinence; urinary urgency as defined by frequent perception of a pressing need to void; urinary frequency as defined by greater than six voiding episodes in an average 12 hour period despite normal fluid intake; nocturia as defined by the need to urinate more than two times in an average night.

Cognition impairment in the case of Probable iNPH patients must involve at least two of the following that cannot be fully attributable to other conditions: psychomotor slowing (increased response latency); difficulty dividing or maintaining attention; memory lapses (especially short-term); executive dysfunction (e.g. impairment in multi-step procedures, working memory, formulation of abstractions/similarities, insight); behavioral or personality changes.

Possible(xii)

If patients do not meet all of the above criteria but are still suspected of iNPH, certain exceptions are permissible for a designation of Possible. The clinical presentation and history may include any of the following six exceptions:

  1. Symptoms have a subacute or indeterminant mode of onset
  2. Symptoms begin at any age following childhood
  3. Symptoms have less than a three month or indeterminant duration
  4. Symptoms remotely follow events such as mild head trauma, intracerebral hemorrhage, childhood and adolescent meningitis, or other conditions that the clinician judges unlikely to be immediately causally related
  5. Symptoms co-exist with other neurologic, psychiatric or general medical disorders that the clinician judges not to be entirely attributable to these conditions
  6. Symptoms are non-progressive or not clearly progressive

For a “Possible” designation, observable gait or balance disturbance is not a mandatory symptom as long as incontinence and/or cognitive impairment are determined. Similarly, gait disturbance or dementia alone can stand as an acceptable sign of iNPH possibility. In brain imaging, evidence of cerebral atrophy of sufficient severity to potentially explain ventricular size is acceptable, as well as the discovery of any structural lesions that might influence ventricular size.

Unlikely(xiii)

Patients should be classified as Unlikely to have iNPH if they do not fulfill the criteria for either Probable or Possible iNPH or if they exhibit any of the following eight items:

  1. Acute presentation of symptoms
  2. Recent history of subarachnoid hemorrhage, meningitis, or brain injury
  3. Signs of increased intracranial pressure such as papilledema
  4. No component of the symptom triad (gait, dementia and incontinence)
  5. Other causes clearly explain findings (i.e. spinal stenosis)
  6. No evidence of ventriculomegaly through brain imaging
  7. Obstructive hydrocephalus revealed through brain imaging
  8. Congenital hydrocephalus revealed through brain imaging

Treatment

With the VP shunt in place, cerebrospinal fluid flows into the ventricular (collection) catheter and down the exit catheter, which shunts the fluid into the peritoneal cavity.

At the time patients are determined to be either iNPH Probable or Possible, they should be referred immediately to a neurosurgeon for further testing and treatment. Of the neurosurgeons interested in diagnosing and treating NPH, CINN neurosurgeon Gail Rosseau, M.D. has cared for close to 50 patients with the condition.

Consistent with the guidelines, following a presumptive diagnosis of NPH, patients will be admitted for a three-day period of lumbar drainage to determine whether symptoms will improve with shunting. If there is improvement in the symptoms following the trial drainage period, a shunt will be implanted, and the symptoms will very likely (and in many cases, immediately) begin the process of reversal.(xiv)

Today, NPH patients also benefit from the latest developments in shunt technology. Whereas in the past, shunt implantation and management meant ongoing, high-risk surgical operations with each relatively frequent flow adjustment, non-invasive adjustable (programmable) valves are now available. These state-of-the-art shunts can be adjusted and fine-tuned magnetically and without additional surgery, providing the lowest risk and most effective NPH treatment available.

It is imperative for NPH, as a progressive condition, to be diagnosed and treated as early as possible. Unfortunately, the more the symptoms advance, the worse their chances are for reversal. Additionally, Marmarou’s study finds that after 75 years of age, a patient has significantly less of a chance for improvement with shunt placement.(xv)

“In the past, physicians would just treat the condition based on the symptoms and the MRI results,” says Rosseau. “The new guidelines really give us an accurate measure of whether a patient will improve through treatment.”

i Codman a Johnson & Johnson company: Normal Pressure Hydrocephalus (NPH) Fact Sheet.

ii Codman a Johnson & Johnson company: Normal Pressure Hydrocephalus (NPH) Presentation.

iii Rachel Fudge, et al: About Normal Pressure Hydrocephalus—A Book for Adults and Their Families (San Francisco: Hydrocephalus Association, 2002), 7.

iv Terry D. Fife: Clinical Features of Normal Pressure Hydrocephalus (Phoenix: Barrow Neurological Institute, 2003), 10.

v Anthony Marmarou: Presentation: Guidelines for Diagnosis and Management of Normal Pressure Hydrocephalus (Chicago: June 25, 2003).

vii Ibid.

viii Rachel Fudge, et al: About Normal Pressure Hydrocephalus—A Book for Adults and Their Families (San Francisco: Hydrocephalus Association, 2002), 8.

ix Anthony Marmarou: Presentation: Guidelines for Diagnosis and Management of Normal Pressure Hydrocephalus (Chicago: June 25, 2003).

x Ibid.

xi Ibid.

xii Ibid.

xiii Ibid.

xiv Ibid.

xv Ibid.