How can you best diagnose idiopathic normal pressure hydrocephalus?

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Clinical Inquiries

How can you best diagnose idiopathic normal pressure hydrocephalus?

J Fam Pract. 2007 November;56(11):947-949

By

Daniel Hunter-Smith, MD

Cleo Pappas, MLIS, AHIP

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EVIDENCE-BASED ANSWER

Diagnose idiopathic normal pressure hydrocephalus (INPH) by clinical history, brain imaging, physical findings, and physiological criteria.

The clinical examination must show the characteristic gait disturbance and either impaired cognition or impaired urinary continence (strength of recommendation [SOR]: B, based on systematic review of small randomized controlled trial [RCT] and prospective trials).

The cerebrospinal fluid (CSF) opening pressure should be between 70 and 245 mm H₂o (SOR: B, based on systematic review of small RCT and prospective trials). No single test has sufficient sensitivity to rule out the diagnosis of INPH (SOR: B, based on systematic review of small RCT and prospective trials).

Clinical commentary

Subtle clues help make the diagnosis
Sumathi Devarajan, MD
Oregon Health and Science University Family Medicine, Portland

Normal pressure hydrocephalus is primarily diagnosed clinically. The classic triad of gait instability, cognitive dysfunction, and urinary incontinence, however, seldom present together. The only promising diagnostic and therapeutic intervention is the response observed with a ventriculoperitoneal shunt. However, this intervention is invasive and not without risks. Neuroimaging plays a role, but only when the clinical suspicion is high.

Therefore, understanding the subtleties in the character of the gait, the time of onset, the progression of dementia, and the onset of urinary incontinence in relationship to one another helps in making the final diagnosis.

Evidence summary

FAST TRACK

To diagnose idiopathic normal pressure hydrocephalus, an exam must reveal the characteristic gait and impairment in either cognition or urinary continence

Current uncertainty in diagnostic criteria makes estimates of the incidence of INPH unclear, but it is thought to cause fewer than 5% of cases of dementia.¹

Two systematic reviews have looked at the question of diagnosing INPH.^2,3 Unfortunately, there is no definitive test or physical finding for INPH. For patients over 40 years of age, INPH has an insidious onset, a progressive course, and lacks an identifiable antecedent cause. A brain imaging study reveals ventricular enlargement not attributable to other causes. Some suggest that the diagnosis be assessed as “probable,” “possible,” and “unlikely” based on the degree of fulfillment of a set of historical, imaging, clinical, and physiological criteria (TABLE).³

TABLE
Categorizing the likelihood of idiopathic normal pressure hydrocephalus³

Probable INPH
HISTORY (MUST FULFILL ALL)
Insidious onset over age 40 Progression over at least 3 to 6 months No evidence of an antecedent event known to cause secondary hydrocephalus No other neurological, psychiatric, or medical condition sufficient to explain the presenting symptoms
BRAIN IMAGING (MUST FULFILL ALL)
ACT or MRI study showing evidence of ventricular enlargement not entirely attributable to cerebral atrophy No macroscopic obstruction to cerebrospinal fluid flow At least 1 of the following: enlargement of the temporal horns of the lateral ventricles, colossal angle>40 degrees, evidence of altered brain water content, flow void on MRI
CLINICAL
Evidence of a gait/balance disturbance must be found, plus at least 1 other area of impairment in cognition, urinary continence, or both
*Gait/balance should reveal at least* 2 of the following 9 items:**
Decreased step height Decreased step length Decreased speed of walking Increased trunk sway during walking Widened standing base Toes out when walking Retropulsion Turning en bloc Impaired walking balance
*Tests of cognition should show evidence of at least* 2 of the following 7 characteristics that are not fully attributable to other conditions:**
Psychomotor slowing Difficulty dividing or maintaining attention Decreased fine motor speed Decreased fine motor accuracy Impaired recent memory formation or executive function, such as insight, performance of multistep procedures, or formation of abstractions/similarities Behavioral changes Personality changes
Symptoms of urinary incontinence not attributable to other primary urological disorders should be present:
Episodic or persistent urinary incontinence Fecal incontinence Any 2 of the following: urinary urgency, urinary frequency (>6 voids per 12 hours), nocturia (>2 voids per night)
PHYSIOLOGICAL
Cerebrospinal fluid opening pressure on lumbar puncture should be in the range of 70–245 mm H₂O (or 5–18 mm Hg)
Possible INPH
HISTORY (MUST FULFILL ALL)
Reported symptoms begin earlier than 40 years of age or show lack of progression There are remote antecedent events such as head trauma, intracerebral hemorrhage or meningitis The coexistence of other neurological, psychiatric, or medical conditions that make it difficult to attribute symptoms to just idiopathic normal pressure hydrocephalus
BRAIN IMAGING (MUST FULFILL ALL)
Cerebral atrophy is sufficient to potentially explain observed hydrocephalus Structural lesions are present that may influence ventricular size
CLINICAL
There are symptoms of incontinence or cognitive impairment without observable gait/balance disturbance Isolated gait/balance disturbance or cognitive impairment is observed
PHYSIOLOGICAL
Opening cerebrospinal fluid pressure has not been measured or it falls outside the required range for probable idiopathic normal pressure hydrocephalus

Evidence-based answers from the Family Physicians Inquiries Network

How can you best diagnose idiopathic normal pressure hydrocephalus?

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