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:
 |
NPH symptoms are insidious
in onset (versus acute) |
|
Symptoms take origin after
age 40 |
|
Symptoms have a duration
of no less than three months |
|
Symptoms are not attributable
to other documented neurologic, psychiatric or general
medical conditions |
|
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:
|
Symptoms have a subacute
or indeterminant mode of onset |
|
Symptoms begin at any age
following childhood |
|
Symptoms have less than a
three month or indeterminant duration |
|
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 |
|
Symptoms co-exist with other
neurologic, psychiatric or general medical disorders
that the clinician judges not to be entirely attributable
to these conditions |
|
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:
|
Acute presentation of symptoms |
|
Recent history of subarachnoid
hemorrhage, meningitis, or brain injury |
|
Signs of increased intracranial
pressure such as papilledema |
|
No component of the symptom
triad (gait, dementia and incontinence) |
|
Other causes clearly explain
findings (i.e. spinal stenosis) |
|
No evidence of ventriculomegaly
through brain imaging |
|
Obstructive hydrocephalus
revealed through brain imaging |
|
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.”
|
