Communicating hydrocephalus with normal CSF pressure presenting as the triad of gait disturbance, urinary incontinence, and dementia.
Also known as: NPH, Hakim-Adams syndrome, idiopathic NPH, iNPH
Overview
A communicating hydrocephalus characterized by ventriculomegaly disproportionate to cortical atrophy, normal CSF opening pressure, and the clinical triad of gait disturbance, cognitive impairment, and urinary incontinence. May be idiopathic or secondary to prior subarachnoid hemorrhage, meningitis, head trauma, or radiation.
Epidemiology
Prevalence ~1.5-3% of adults >65; rises with age. Often underdiagnosed because triad mimics common comorbidities. Slight male predominance.
Try two board-style Normal Pressure Hydrocephalus questions
Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.
Question 1NeurologyEasy
A 75-year-old male has a 3-month history of progressive gait difficulty described as magnetic (feet stuck to floor), urinary incontinence, and cognitive decline. He denies headaches or falls. MRI shows dilated lateral ventricles with an Evans index of 0.36, disproportionate to cortical atrophy, and no aqueductal obstruction. Lumbar puncture (LP) shows opening pressure 12 cmH2O and removal of 50 mL CSF markedly improves his gait immediately. Which of the following is the most likely diagnosis?
ASubcortical vascular dementia
BParkinson disease
CChronic subdural hematoma
DAlzheimer disease
ENormal pressure hydrocephalus
Reveal answer & full explanation
Correct answer: E — Normal pressure hydrocephalus
ASubcortical vascular dementia
BParkinson disease
CChronic subdural hematoma
DAlzheimer disease
ENormal pressure hydrocephalus✓
Why Normal pressure hydrocephalus is correct
Normal pressure hydrocephalus (NPH) presents with the classic Hakim-Adams triad: gait apraxia (most prominent; magnetic gait with wide-based shuffling), urinary incontinence, and dementia (frontal-subcortical pattern).
Diagnosis is supported by hydrocephalus on MRI with an Evans index above 0.3 and disproportionately large ventricles relative to cortical atrophy.
Lumbar puncture (LP) opening pressure is normal (about 7-24.5 cmH2O, i.e., 5-18 mm Hg per the Relkin criteria) or low-normal despite dilated ventricles — hence the term normal pressure.
Large-volume tap test (removal of 30-50 mL CSF): immediate gait improvement after LP predicts ventriculoperitoneal (VP) shunt response (sensitivity 50-60%).
Why the others are wrong
Alzheimer disease — Alzheimer produces cortical atrophy and amnestic dementia, not magnetic gait with ventriculomegaly disproportionate to atrophy or tap-test gait improvement (anchoring on cognitive decline).
Chronic subdural hematoma — a classic reversible cause of gait decline, incontinence, and confusion in an older adult, but imaging would show a crescentic extra-axial collection with mass effect rather than symmetric ventricular enlargement disproportionate to atrophy, and gait would not improve after a large-volume tap (treatable-mimic-wrong-imaging).
Subcortical vascular dementia — small-vessel ischemic disease mimics all three triad elements (small-stepped gait, urinary urgency, executive dysfunction), but MRI shows confluent white matter disease and lacunes with ventricular enlargement proportional to atrophy, and gait does not improve after a large-volume tap (right-triad-wrong-mechanism).
Parkinson disease — its shuffling gait, urinary urgency, and later cognitive decline can mimic the triad, but Parkinson disease requires bradykinesia with rest tremor or rigidity, does not cause ventricular enlargement disproportionate to atrophy, and its gait does not improve after a large-volume tap (look-alike gait disorder).
Additional high-yield points
Definitive treatment is VP shunt, which improves gait in 70-80% of patients; cognitive symptoms respond less reliably.
Extended LP drainage trial is more predictive of shunt response than a single LP.
Gait responds best to shunting; dementia responds least well.
Question 2NeurologyMedium
A 74-year-old man is brought in by his daughter for 8 months of progressive walking difficulty. He takes short, shuffling steps and feels as though his feet are "stuck to the floor," and he has had two falls. Over the same period he has become more forgetful and apathetic and has developed urinary urgency with occasional incontinence. CBC, BMP, TSH, vitamin B12, and RPR are normal, and urinalysis shows no infection. MRI of the brain shows ventriculomegaly with an Evans index of 0.36 disproportionate to cortical atrophy and no aqueductal obstruction. Which of the following is the most appropriate next diagnostic test?
AHigh-volume diagnostic lumbar puncture
BFluorodeoxyglucose (FDG) PET brain scan
CWhole-spine MRI with gadolinium contrast
DIndium-111 radionuclide cisternography
EDopamine transporter (DaT) SPECT scan
Reveal answer & full explanation
Correct answer: A — High-volume diagnostic lumbar puncture
AHigh-volume diagnostic lumbar puncture✓
BFluorodeoxyglucose (FDG) PET brain scan
CWhole-spine MRI with gadolinium contrast
DIndium-111 radionuclide cisternography
EDopamine transporter (DaT) SPECT scan
Why High-volume diagnostic lumbar puncture is correct
The clinical triad (magnetic gait, frontal-subcortical cognitive decline, urge incontinence) plus MRI ventriculomegaly (Evans index >0.3) without obstruction meets probable idiopathic normal pressure hydrocephalus by the Relkin/Marmarou criteria.
A large-volume tap test removes 30-50 mL of CSF and lets you reassess gait and cognition before and after drainage; gait improvement after drainage is the most reliable predictor of ventriculoperitoneal shunt response, and the procedure also documents a normal CSF opening pressure (70-245 mm H2O, or 7-24.5 cm H2O).
A negative tap test has limited sensitivity, so a non-responder with high suspicion can proceed to an extended lumbar drainage trial; the tap test is still the correct first confirmatory step.
Why the others are wrong
Dopamine transporter (DaT) SPECT scan distinguishes Parkinson disease from essential tremor; NPH gait is magnetic without festination or asymmetric rest tremor, and a DaT scan neither confirms NPH nor predicts shunt response.
Fluorodeoxyglucose (FDG) PET brain scan separates Alzheimer disease from frontotemporal dementia by their hypometabolism patterns, but it neither confirms idiopathic normal pressure hydrocephalus nor predicts shunt response, and ventriculomegaly disproportionate to cortical atrophy already favors NPH over a primary neurodegenerative dementia.
Whole-spine MRI with gadolinium contrast targets cord pathology such as tumor, infection, or inflammatory myelitis, and gadolinium is not needed for degenerative lumbar stenosis; stenosis gait worsens with walking and improves with forward flexion, and it would not explain the cognitive decline, incontinence, or ventriculomegaly.
Indium-111 radionuclide cisternography — isotope cisternography was historically used in suspected NPH to show delayed tracer clearance and reflux into the ventricles, but it does not improve prediction of shunt response over clinical and MRI criteria, so it is no longer part of the standard workup and the tap test has replaced it as the confirmatory step.
That's 2. Get 7,700+ more.
Unlock the full FirstPassPA bank: 7,700+ board-style questions, flashcards, and an AI tutor that explains every answer. Your 7-day free trial includes everything, and there's no credit card required.
You've read your 2 free diagnosis previews. Create your free account to unlock the full Normal Pressure Hydrocephalus outline — plus all 514 diagnoses, 7,700+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
History of subarachnoid hemorrhage, meningitis, or significant head trauma (secondary NPH)
Vascular comorbidities — hypertension, diabetes, white matter disease
Family history (rare familial forms)
Pathophysiology
Impaired CSF absorption at arachnoid granulations, possibly with altered CSF dynamics and reduced compliance, leads to ventricular enlargement. Stretched periventricular tracts, particularly the corona radiata and corpus callosum, impair frontal and motor function. Coexisting Alzheimer pathology is common and confounds outcomes.
Clinical presentation
Symptoms
Gait disturbance — the earliest and most characteristic feature; magnetic, shuffling, broad-based, with difficulty initiating ('feet stuck to floor')
Probable iNPH (Relkin/Marmarou 2005): progressive gait disturbance + at least one additional triad feature + ventriculomegaly without obstruction + normal CSF opening pressure (5-18 mm Hg, i.e., 70-245 mm H2O or about 7-24.5 cm H2O, on LP), with insidious onset after age 40, symptoms lasting at least 3 months, and no antecedent cause such as head trauma, hemorrhage, or meningitis.
Urinalysis to exclude UTI as incontinence contributor
Imaging
MRI brain — ventriculomegaly (Evans index >0.3) disproportionate to cortical atrophy, with effaced cortical sulci over the convexity and dilated Sylvian fissures (DESH pattern: disproportionately enlarged subarachnoid space hydrocephalus)
No aqueductal obstruction (distinguishes from obstructive hydrocephalus)
CSF flow void through aqueduct on MRI
Large-volume lumbar puncture ('tap test') — remove 30-50 mL CSF; reassess gait and cognition before and ~1-24 h after
Extended lumbar drainage trial (3 days, 10 mL/h) — higher sensitivity than single tap
Exclude or document comorbid Alzheimer pathology (CSF Aβ/tau, amyloid PET) — predicts more limited shunt response
Post-shunt management
Adjust programmable valve pressure for symptom control vs overdrainage (subdural collections)
Routine surveillance for shunt failure: recurrence of gait/cognitive symptoms
Physical therapy and gait training to consolidate gains
Second-line / adjunct
Acetazolamide and serial LPs — temporizing measures only; not durable
Cognitive rehabilitation and behavioral strategies for residual deficits
Complications
Shunt malfunction (mechanical or infectious) — re-presentation with declining gait
Subdural hematoma from overdrainage (more common with non-programmable valves)
Shunt infection (~5%, higher in early postoperative period)
Persistent cognitive impairment if AD pathology coexists
Falls, urinary tract infection, deconditioning
PANCE pearls
Gait disturbance is the symptom most likely to improve with shunting; isolated dementia rarely responds.
Evans index = maximal frontal horn width / maximal inner skull diameter on the same axial slice; >0.3 supports ventriculomegaly.
Disproportionately enlarged subarachnoid space hydrocephalus (DESH) on coronal MRI is a strong imaging predictor of shunt response.
Tap test high specificity but limited sensitivity — a negative tap test does not exclude shunt-responsive NPH.
Coexisting Alzheimer pathology is the most common reason for limited shunt response — counsel families accordingly.
References
Relkin 2005 — Relkin N et al. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery 2005;57(3 Suppl):S4-S16.
Japanese Society of NPH Guidelines (3rd ed.) — Nakajima M et al. Guidelines for management of idiopathic normal pressure hydrocephalus (third edition). Neurol Med Chir (Tokyo) 2021;61:63-97.
AAN 2015 Practice Guideline — Halperin JJ et al. AAN practice guideline: Idiopathic normal pressure hydrocephalus: Response to shunting and predictors of response. Neurology 2015;85:2063-2071.
Practice Neurology questions on FirstPassPA
Turn this outline into retention. 7,700+ board-style questions with an AI tutor that explains every answer — free to start, no card required.
Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.