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GERICLINICS

GeriQBank · Paper III · Q10

Normal pressure hydrocephalus

Moderate YieldAsked ×17-mark note
Topic
Dementia & Cognition
Chapter
Dementia & Cognitive Disorders
Years asked
Not recorded in the source
Frequency
Set 1× in Paper III (2009–2025)

As set in the university paper

  • Normal pressure hydrocephalus.

    Paper III · Cognition, Dementia & Delirium · asked ×1 · 7-mark note · see in paper list

Answer framework

  1. Definition and concept — communicating hydrocephalus with normal pressure; idiopathic versus secondary
  2. Aetiology and pathophysiology — impaired absorption and flow; periventricular stress; comorbid vascular disease
  3. Clinical presentation — the Hakim–Adams triad; gait; cognition; urinary symptoms
  4. Differential diagnosis — small-vessel vascular disease and other mimics
  5. Diagnostic modalities — imaging (Evans index, callosal angle, DESH); neuropsychology
  6. Prognostic tests — tap test; lumbar drain; infusion test and ICP; other modalities; rising predictive power
  7. Treatment — shunt types and valves; patient selection; complications and follow-up
  8. Recent updates — the PENS trial; Cochrane; guidelines and shunt comparisons; prevalence; India

An exam answer plan drawn from the detailed answer below. Use it to attempt the question first.

Detailed answer

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Attempt it firstOutline your answer as a 7-mark note before revealing it — definition, causes, evaluation, management and the geriatric angle.Reveal answer

Short revision answer

  • NPH is a chronic communicating hydrocephalus with enlarged ventricles but normal mean CSF opening pressure, presenting with a classic triad — one of the few potentially reversible dementias. It is idiopathic (iNPH) or secondary (after SAH, meningitis, head injury or surgery).
  • Mechanism: impaired CSF absorption and altered flow; enlarged ventricles stress the periventricular white matter (corona radiata fibres to the legs first, then the frontal–subcortical circuits for executive and bladder control). Comorbid cerebrovascular disease is common and limits shunt response.
  • Hakim–Adams triad ("wet, wacky, wobbly"): gait comes first and is most likely to improve — magnetic, broad-based and shuffling, with start hesitation, freezing and en bloc turning, but preserved arm swing and no tremor; subcortical/frontal cognition (slowing, inattention, executive dysfunction, apathy) with language and praxis preserved; urgency → urge incontinence → indifferent incontinence.
  • Differential: small-vessel vascular disease produces the triad more often than NPH; also Parkinson's, PSP, MSA, AD, DLB, cervical myelopathy, chronic subdural haematoma and hydrocephalus ex vacuo.
  • Imaging: ventriculomegaly out of proportion to sulcal atrophy — Evans index >0.3, periventricular hyperintensities, a bowed corpus callosum, callosal angle <90°, aqueductal flow void; DESH (large Sylvian fissures, tight high-convexity sulci) strongly supports it. Neuropsychology documents the profile and gives a baseline.
  • Predicting shunt response: tap test (30–50 mL with gait and cognitive testing — good positive but poor negative predictive value); extended lumbar drainage over 2–3 days (the best predictor); infusion test (outflow resistance), ICP B-waves, phase-contrast MRI; the iNPH grading scale. Predictive power rises from clinical/imaging → tap test → infusion test → lumbar drainage.
  • Treatment: ventriculoperitoneal shunt (standard), ventriculoatrial or lumboperitoneal; programmable valves and anti-siphon devices limit overdrainage; acetazolamide only temporises. Select carefully (duration, vascular disease, coexisting AD, frailty, anaesthetic risk, expectations). Complications: infection, obstruction, overdrainage with subdural collection, seizures, revision. Gait improves most; results are best with short duration and little comorbidity.
  • Updates: PENS (NEJM, December 2025; 99 patients, 17 centres) compared open with placebo-closed valves after shunting: gait velocity +0.23 vs +0.03 m/s (difference 0.21), meaningful improvement 80% vs 24%, with better balance and fewer falls; cognition and continence did not improve at 3 months. It stopped early for efficacy, answering the 2024 Cochrane call for more trials.
  • Guidelines: AAN/AANS/CNS reaffirmed in July 2024; Japanese guidelines (2020); SINPHONI-2 found lumboperitoneal shunting comparable to VP, and RASHOMON is comparing all three. Prevalence is higher than thought — up to 1.5% in the late 60s and 7.7% at 80–86. India: often dismissed as "ageing gait"; shunting is available and cheap — measure the Evans index on the CT already done.

Condensed by GeriClinics from the detailed answer below, with no new facts added.

15–20 High-Yield Points

A. DEFINITION AND CONCEPT

1.

Normal pressure hydrocephalus (NPH) is a chronic communicating hydrocephalus with ventricular enlargement in the presence of normal mean cerebrospinal fluid opening pressure, presenting with a characteristic clinical triad and being one of the few potentially reversible causes of dementia.

2.

It is classified as idiopathic (iNPH) or secondary, the latter following subarachnoid haemorrhage, meningitis, head injury or intracranial surgery. It appears in every standard list of potentially reversible dementias and of causes of parkinsonism with cognitive impairment in the elderly.

B. AETIOLOGY AND PATHOPHYSIOLOGY

3.

The classical model is one of impaired CSF absorption at the arachnoid granulations with altered CSF flow dynamics, described through bulk-flow theory; CSF flow and CSF flow rate abnormalities are central to both pathogenesis and diagnosis.

4.

Ventricular enlargement transmits periventricular tissue stress, producing ischaemia and disruption of the periventricular white matter, particularly the corona radiata fibres to the medial legs — explaining why gait is affected first and most severely, and why the frontal-subcortical circuits subserving executive function and bladder inhibition are next affected.

5.

Comorbid cerebrovascular disease is very common in this age group and both contributes to the clinical picture and limits the response to shunting — an essential caveat when counselling patients.

C. CLINICAL PRESENTATION

6.

Hakim and Adams’ triad: gait disturbance, cognitive impairment (dementia) and urinary incontinence — traditionally remembered as “wet, wacky and wobbly”. Gait disturbance usually appears first and is the symptom most likely to improve with treatment.

7.

The gait is classically “magnetic” — broad-based, shuffling, with reduced step height and length, start hesitation, freezing and difficulty turning (en bloc turning), but with preserved arm swing and no tremor, distinguishing it from Parkinson’s disease. NPH is also listed among the causes of secondary parkinsonism.

8.

Cognitive impairment is subcortical/frontal — psychomotor slowing, inattention, executive dysfunction and apathy — with relatively preserved cortical functions (language, praxis, recognition), distinguishing it from AD.

9.

Urinary symptoms begin as urgency and frequency and progress to urge incontinence, and later to an indifferent incontinence reflecting frontal disinhibition.

D. DIFFERENTIAL DIAGNOSIS

10.

The crucial differential is subcortical ischaemic vascular disease (SIVD): the textbook makes the point explicitly that the triad of dementia, urinary incontinence and gait disturbance is more often produced by small-vessel vascular dementia than by NPH. Other differentials include Parkinson’s disease and atypical parkinsonian syndromes (PSP, MSA), Alzheimer’s disease, DLB, cervical spondylotic myelopathy, chronic subdural haematoma and hydrocephalus ex vacuo from cerebral atrophy.

E. DIAGNOSTIC MODALITIES

11.

CT and MRI demonstrate ventriculomegaly disproportionate to sulcal atrophy, quantified by an Evans index >0.3 (maximum frontal horn width divided by maximum inner skull diameter), with periventricular hyperintensities, upward bowing of the corpus callosum, a callosal angle below 90 degrees, and a CSF flow void or increased aqueductal flow.

12.

Disproportionately enlarged subarachnoid space hydrocephalus (DESH) is a key morphological pattern — enlarged Sylvian fissures and basal cisterns with tight, compressed high-convexity and medial parietal sulci — and strongly supports the diagnosis.

13.

Neuropsychological testing documents the subcortical/frontal profile, provides the objective baseline against which CSF-drainage response is measured, and helps identify coexisting AD or vascular disease.

F. PROGNOSTIC (SUPPLEMENTARY) TESTS — PREDICTING SHUNT RESPONSE

14.

Lumbar puncture (the “tap test”) — removal of a large volume of CSF (30–50 mL) with objective gait and cognitive testing before and after. It has good positive but poor negative predictive value, so a negative tap test does not exclude a shunt-responsive patient.

15.

Extended lumbar drainage (lumbar drain trial) — continuous external drainage over 2–3 days with serial testing; this has the highest predictive accuracy of the supplementary tests. Lumbar infusion test (intrathecal infusion test) measures CSF outflow resistance (Rout); intracranial pressure monitoring detects B-waves.

16.

Additional modalities include phase-contrast MRI for aqueductal CSF stroke volume, magnetic resonance spectroscopy, SPECT and PET. Grading uses the idiopathic normal-pressure hydrocephalus grading scale (iNPHGS), which scores each of the three triad domains.

17.

The value of provocative CSF removal is quantitative: predictive power for a positive shunt response rises progressively as one moves from clinical and imaging information alone → plus tap test → plus infusion testing → plus external lumbar drainage.

G. TREATMENT

18.

Shunt surgery is the definitive treatment. Options are ventriculoperitoneal shunting (the standard), ventriculoatrial shunting and lumboperitoneal shunting; endoscopic third ventriculostomy has a limited role in communicating NPH. Programmable (adjustable) valves allow non-invasive post-operative pressure adjustment and reduce the risk of overdrainage; anti-siphon devices are added for the same reason. Drug therapy (acetazolamide) has only a marginal, temporising role.

19.

Patient selection and shared decision-making are paramount — weighing symptom duration, degree of comorbidity (especially cerebrovascular disease and coexisting AD), frailty, anaesthetic risk and realistic expectations of benefit.

20.

Risks and complications: shunt infection and shunt obstruction are the principal shunt-related problems, along with overdrainage causing subdural effusion or haematoma, seizures, and the need for revision surgery. Long-term care and follow-up are mandatory, with periodic valve setting review and prompt imaging for any deterioration. Outcome is best for gait, less certain for cognition and continence, and better with shorter symptom duration and less comorbidity.

Latest Updates (2023–Present)

The PENS trial (Placebo-Controlled Effectiveness in iNPH Shunting; NEJM, December 2025) is the landmark update. This international, multicentre, double-blind, randomised, placebo-controlled trial enrolled 99 patients across 17 centres in the USA, Canada and Sweden, randomising participants after shunt insertion to an open versus a placebo (closed) valve setting. Gait velocity increased by 0.23 m/s with an open shunt versus 0.03 m/s with placebo — a treatment difference of 0.21 m/s (95% CI 0.12 to 0.31; p<0.001). The DSMB stopped enrolment early at the second interim analysis for efficacy.

What PENS did and did not show: 80% of the open-shunt group achieved meaningful improvement versus 24% of the placebo group, with better balance and fewer falls. Cognition and incontinence did not improve significantly at 3 months — a nuance that should be quoted, because it aligns exactly with the classical teaching that gait is the symptom most likely to respond.

The 2024 Cochrane review on shunting for iNPH had concluded that further trials were needed to increase certainty; PENS has now supplied that evidence and has effectively ended the call for a moratorium on shunt surgery.

Guidelines: the AAN/AANS/CNS guideline on iNPH response to shunting and predictors of response was reaffirmed in July 2024; the Japanese iNPH clinical practice guidelines (3rd edition, 2020) remain the most detailed, though they do not compare ventriculoperitoneal, lumboperitoneal and ventriculoatrial shunting directly — a gap the ongoing RASHOMON registry study is designed to fill. SINPHONI-2 had earlier shown lumboperitoneal shunting to be comparable to ventriculoperitoneal shunting.

Epidemiology has been revised upward. Population-based MRI studies indicate iNPH affects up to 1.5% of people in their late 60s and as many as 7.7% of adults over 80–86, making it far commoner and more under-diagnosed than previously assumed, and reinforcing the case for active case-finding in falls and gait clinics. Indian context: iNPH is systematically under-recognised and often labelled as “ageing gait”, vascular parkinsonism or AD. Given that neurosurgical shunting is widely available across Indian tertiary centres and is relatively inexpensive, the diagnostic bottleneck is clinical suspicion, not treatment access. Every older adult presenting with a gait disorder plus cognitive slowing — a very common presentation to NPHCE district geriatric clinics and falls services — deserves an Evans index measured on the CT that has usually already been done.

Current Practice Update

Current evidence and guidelines (2023

Area Textbook position onward)

Evidence for shunting Treatment of choice, but efficacy debated PENS trial (2025) provides randomised, and outcome variable placebo-controlled proof: gait velocity gain 0.21 m/s; 80% vs 24% meaningful improvement Which symptom responds Gait responds best Confirmed: gait and balance improve; cognition and continence did not improve significantly in PENS Prevalence Uncommon cause of dementia Up to 1.5% in late 60s and 7.7% over 86 — substantially under-diagnosed Shunt type VP, VA, LP shunts described without direct SINPHONI-2: LP comparable to VP; comparison RASHOMON registry is comparing all three prospectively Patient selection Supplementary CSF tests improve predictive Unchanged and reinforced — extended power lumbar drainage remains the best predictor Exam One-Liners NPH = ventriculomegaly with normal mean CSF opening pressure.

Hakim–Adams triad: gait disturbance, dementia, urinary incontinence (“wobbly, wacky, wet”). Gait comes first and responds best.

Gait is magnetic, broad-based, with start hesitation and en bloc turning, but preserved arm swing. Cognition is subcortical/frontal — slowing, inattention, executive dysfunction, apathy. Evans index >0.3; callosal angle <90°; DESH pattern supports the diagnosis.

Small-vessel vascular dementia produces the triad more often than NPH does.

Tap test: good positive, poor negative predictive value; extended lumbar drainage is the best predictor. Predictive power rises: clinical/imaging → tap test → infusion test → external lumbar drainage. Treatment = VP shunt with a programmable valve; complications are infection, obstruction and overdrainage with subdural collection.

PENS trial 2025: gait velocity gain 0.21 m/s, 80% vs 24% meaningful improvement; no significant cognitive or continence benefit.

CONSOLIDATED RAPID-REVISION GRID

The Ten Answers on One Page

The single fact most likely to earn the # Topic mark 1 Dementia and management ChEI for mild–moderate AD, memantine for moderate–severe; DOMINO supports continuing donepezil; Lancet Commission 2024: 14 risk factors, 45% preventable 2 Dementia (repeat) India — LASI-DAD: 7.4%, 8.8 million, 16.9 million by 2036 3 MCI Four core criteria; 15–20% convert per year; anti-amyloid antibodies now licensed at the MCI stage 4 Reversible dementias <4% truly reversible; drugs are the commonest contributor; treatment does not guarantee reversal 5 Behavioural symptoms 90–98% develop at least one NPS; DICE; caregiver interventions outperform antipsychotics 6 Four common dementias AD = hippocampus/temporoparietal; VaD = vessel-size dependent; DLB = cortical Lewy bodies with occipital hypometabolism; FTD = frontal/anterior temporal 7 Tau / progranulin / TDP-43 >95% of FTLD = TDP-43 (50–60%) or tau (35–45%); MAPT → tau, GRN and VCP → TDP-43 8 Pick’s disease Pick bodies = 3R tau-positive argyrophilic inclusions, densest in the dentate gyrus 9 Lewy body dementia Four core features; probable = 2 core, or 1 core + 1 indicative biomarker; ChEIs effective, avoid conventional neuroleptics 10 Normal pressure hydrocephalus Hakim–Adams triad; Evans index >0.3; PENS 2025 — gait improves, cognition and continence do not Cross-Cutting Indian Policy Points to Weave Into Any Dementia Answer LASI-DAD: dementia prevalence 7.4% in those 60+, 8.8 million cases, projected 16.9 million by 2036; higher in women and rural populations India Ageing Report 2023 (UNFPA): 60+ population to reach 20.8% by 2050 NPHCE — Regional Geriatric Centres, district geriatric units, geriatric clinics at CHC/PHC level, the delivery platform for cognitive screening National Mental Health Programme / District Mental Health Programme — the practical route for BPSD and caregiver support AB-PMJAY and the Ayushman Vay Vandana Card — universal ₹5 lakh cover for all citizens aged 70 and above regardless of income Maintenance and Welfare of Parents and Senior Citizens Act, 2007 — legal remedy for neglect and abandonment, highly relevant to dementia caregiving breakdown Rights of Persons with Disabilities Act, 2016 — includes chronic neurological conditions and mental illness, enabling disability certification in young-onset dementia Rashtriya Vayoshri Yojana and AVYAY — assistive devices and senior citizen welfare schemes Elder Line 14567 — national toll-free helpline for older adults ARDSI (Alzheimer’s and Related Disorders Society of India) — Dementia India reports, caregiver training, day care and support groups WHO ICOPE (2nd edition) — cognitive decline is one of the six domains of intrinsic capacity screened in primary care End of compilation — Questions 1 to 10, Dementia and Cognitive Disorders.

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