Nervous System & Special Senses

Normal pressure hydrocephalus: triad and treatment

Clinical Overview and When to Suspect Normal Pressure Hydrocephalus

— Prevalence rises sharply after age 60; estimated 0.5–3% of adults >65, higher in those >80.

— Often underdiagnosed: studies suggest up to 10% of dementia evaluations have features of NPH.

— Idiopathic NPH (iNPH) is most common; secondary NPH follows subarachnoid hemorrhage, meningitis, traumatic brain injury, or prior cranial surgery.

— Impaired CSF absorption at arachnoid granulations → chronic ventricular distention → stretching of periventricular white matter tracts (especially corona radiata fibers to lower extremities and frontal subcortical circuits).

— Despite enlarged ventricles, ICP normalizes over time, but compliance is abnormal with intermittent pressure waves.

— Older patient referred for "dementia workup" who also has gait disturbance preceding cognitive change and urinary urgency/incontinence.

— Family complains the patient "walks like their feet are stuck to the floor" or has had unexplained falls.

— Patient with prior SAH, meningitis, or TBI who later develops gait + cognitive decline.

Definition: Normal pressure hydrocephalus (NPH) is a communicating hydrocephalus with ventriculomegaly out of proportion to sulcal atrophy and normal opening pressure on lumbar puncture (typically <245 mm H₂O), producing a reversible dementia syndrome in older adults.

Epidemiology:

Pathophysiology (working model):

When to suspect on Step 3:

Step 3 management: In the ambulatory dementia evaluation, gait assessment is mandatory — gait apraxia disproportionate to cognitive impairment should trigger MRI brain looking for ventriculomegaly. Do not anchor on "Alzheimer disease" before excluding NPH, because NPH is one of the few potentially reversible dementia causes.

Why it matters: Early recognition → shunt → measurable functional recovery; delayed recognition → irreversible white matter injury and persistent disability even after CSF diversion.

Presentation Patterns and Key History

— Gait disturbance — earliest and most responsive to treatment.

— Urinary incontinence — typically urgency first, progressing to frank incontinence with frontal indifference ("I don't care that I wet myself").

— Cognitive impairment — subcortical/frontal pattern: psychomotor slowing, executive dysfunction, apathy, poor attention.

— Gait → urinary → cognitive is the prototypical sequence and is most predictive of shunt responsiveness.

— Cognitive symptoms appearing first should push you toward Alzheimer disease, frontotemporal dementia, or vascular dementia rather than iNPH.

— Magnetic / apraxic gait — feet appear glued to floor, broad-based, short shuffling steps, reduced step height, en-bloc turning (multiple small steps to pivot).

— Preserved arm swing (unlike Parkinson disease).

— Patients can often "bicycle" their legs while supine — gait disorder is out of proportion to limb strength.

— Subcortical dementia: slow processing, impaired set-shifting, decreased verbal fluency.

— Memory storage relatively preserved early — patients benefit from cueing, unlike Alzheimer disease where encoding fails.

— Falls, near-falls, fear of walking.

— Nocturia and frequency before frank incontinence.

— Onset over months, not days (acute = think obstructive hydrocephalus or stroke).

— Prior SAH, meningitis, head trauma, intracranial surgery → secondary NPH.

— Medication review: anticholinergics, sedatives, opioids can mimic or worsen all three triad components.

Classic Hakim–Adams triad ("wet, wobbly, wacky"):

Order of symptom onset matters:

Gait description (high-yield):

Cognitive features:

History pearls to elicit:

Key distinction: In NPH, gait precedes cognition; in Alzheimer disease, memory precedes gait; in Lewy body dementia, visual hallucinations and parkinsonism dominate; in vascular dementia, stepwise decline with focal deficits. Anchoring on this sequence alone often gets you the right answer on the exam.

Physical Exam Findings and Bedside Assessment

— Observe rise from chair, initiation, stride length, step height, turning, tandem gait.

— NPH shows wide base, short shuffling steps, low foot clearance, multistep en-bloc turns, and start hesitation.

— Timed Up and Go (TUG): >13.5 seconds suggests fall risk; record baseline before any tap test.

— 10-meter walk test: measure time and step count — used as objective pre/post tap-test marker.

— Strength, sensation, and cerebellar testing are typically normal — a key feature distinguishing NPH from stroke or myelopathy.

— DTRs and Babinski usually normal; brisk reflexes or sustained clonus should prompt search for cervical myelopathy.

— No resting tremor, no cogwheel rigidity (those suggest Parkinson disease).

— Frontal release signs (grasp, palmomental, glabellar) may be present.

— MoCA preferred over MMSE — MoCA captures executive/frontal deficits (trails, clock, fluency) that MMSE misses.

— Expect impaired Trail Making B, reduced verbal fluency, slowed digit-symbol substitution.

— Postural BP to exclude orthostatic causes of falls.

— Visual acuity and hearing — sensory deprivation worsens cognitive testing.

— Bladder exam, postvoid residual to characterize incontinence.

— Skin and feet for neuropathy mimics.

— Document baseline gait video or photos of footprints if available — used to compare post–tap test.

Gait examination (the single most important exam):

Neurologic exam:

Cognitive bedside testing:

Other exam components:

Hemodynamic / functional baseline:

Board pearl: A patient with magnetic gait, preserved strength, normal reflexes, and frontal-pattern cognitive deficits is NPH until proven otherwise. If you find focal weakness, sensory level, or hyperreflexia, you are likely looking at cervical myelopathy, parasagittal meningioma, or stroke — re-examine the differential before ordering a shunt evaluation.

Diagnostic Workup — Initial Labs and Imaging

— CBC, CMP, TSH, vitamin B12, HIV, RPR/treponemal test.

— Consider HbA1c, folate, vitamin D, depression screen (PHQ-9).

— Urinalysis to exclude UTI-driven delirium overlay.

— Ventriculomegaly disproportionate to sulcal atrophy — the cardinal finding.

— Evans index >0.3 (maximal width of frontal horns ÷ maximal internal skull diameter at the same axial slice).

— Callosal angle <90° on coronal slices through posterior commissure — highly suggestive of iNPH.

— DESH pattern (Disproportionately Enlarged Subarachnoid space Hydrocephalus): tight high-convexity/medial sulci with widened sylvian fissures.

— Periventricular transependymal flow (T2/FLAIR hyperintensity around horns) — supports active CSF dynamics abnormality.

— Aqueductal flow void on T2 — often prominent.

— Significant cortical atrophy, mesial temporal atrophy, or hippocampal volume loss (those suggest Alzheimer).

— Focal infarcts or extensive deep white matter disease (suggests vascular dementia, though mild changes can coexist).

— Mass lesion or obstructive cause (tumor, aqueductal stenosis) — these are non-communicating hydrocephalus, managed differently.

Step 1: Exclude reversible dementia mimics with labs (standard dementia workup):

Step 2: Neuroimaging — MRI brain without contrast is the test of choice:

CT head is acceptable if MRI contraindicated — shows ventriculomegaly and Evans index but misses callosal angle and DESH nuance.

What you do NOT expect:

Step 3 management: In an outpatient with the triad, order MRI brain without contrast as the first imaging study, alongside a reversible-dementia lab panel. Do not jump to lumbar puncture before imaging — you need to exclude mass effect and confirm communicating ventriculomegaly. Document Evans index and callosal angle when you read the report; these become baseline metrics if the patient proceeds to shunt evaluation.

Board pearl: Evans index >0.3 + callosal angle <90° + DESH = imaging triad strongly favoring shunt-responsive iNPH.

Diagnostic Workup — Confirmatory CSF Testing

— Opening pressure should be normal: 70–245 mm H₂O (7–24 cm H₂O). Elevated pressure suggests pseudotumor or obstructive hydrocephalus instead.

— Send CSF for cell count, protein, glucose, VDRL, and consider 14-3-3/tau if prion disease suspected — but in classic iNPH these are normal.

— Remove 30–50 mL of CSF in a single session.

— Perform pre-tap and post-tap (within 2–24 hours, often again at 24–72 hours) standardized assessments: TUG, 10-meter walk time, step count, MoCA.

— Positive response: ≥10–20% improvement in gait speed or TUG; cognitive improvement is supportive but less reliable.

— Sensitivity ~50–80%, specificity high (~75%) for shunt response — negative tap does not exclude shunt-responsive NPH.

— Indwelling lumbar catheter draining ~10 mL/hr for 3–5 days in inpatient setting.

— Higher sensitivity (~80–95%) than single tap; used when single tap is negative but clinical suspicion remains high.

— Risks: infection, nerve root irritation, post-LP headache, overdrainage.

— Measures resistance to CSF outflow; Rout >12–18 mm Hg/mL/min supports diagnosis. Used in specialized centers.

— DAT scan if parkinsonism is prominent to exclude PD/atypical parkinsonism.

— FDG-PET if Alzheimer comorbidity suspected (temporoparietal hypometabolism).

Lumbar puncture with opening pressure (the diagnostic anchor):

Large-volume tap test (CSF tap test):

Extended lumbar drainage (ELD):

CSF infusion test / outflow resistance (Rout):

Ancillary imaging in select cases:

CCS pearl: On a CCS case, after confirming MRI findings, admit (or schedule day-procedure) for large-volume LP with pre- and post-tap gait timing. Document TUG before, TUG after, and order neurosurgery consult if the tap is positive. Do not order shunt placement directly from clinic without objective tap-test data — the exam rewards stepwise confirmation before invasive intervention.

Risk Stratification and Shunt Candidacy Logic

— Gait disturbance as the presenting and dominant symptom.

— Short duration of symptoms (<2 years from onset to evaluation).

— Mild–moderate cognitive impairment (MoCA generally >21).

— Known secondary cause (post-SAH, post-meningitis) — historically excellent response.

— Positive tap test or extended lumbar drainage.

— Imaging: Evans >0.3, callosal angle <90°, DESH pattern, absent or minimal hippocampal atrophy.

— Severe dementia (MoCA <15, MMSE <20) — limited cognitive recovery expected.

— Long-standing symptoms (>3 years).

— Extensive white matter disease or cortical atrophy on MRI.

— Significant comorbid Alzheimer pathology (positive amyloid PET, biomarker evidence).

— Wheelchair-bound or bed-bound at baseline (rehab potential limited).

— Severe comorbidity that increases surgical risk (active anticoagulation, advanced CHF, frailty index high).

— Quote realistic outcomes: 60–80% of well-selected patients improve in gait, 30–50% show cognitive improvement, continence improvement variable.

— Discuss complication rates (shunt infection, malfunction, subdural hematoma — see chunk 11).

— Set functional goals (e.g., independent ambulation, reduced fall risk) rather than "cure."

Goal of workup: Identify patients with the highest probability of meaningful, durable shunt response while avoiding shunting patients who will not benefit and will only incur surgical risk.

Favorable predictors of shunt response:

Unfavorable predictors:

Shared decision-making framework:

Step 3 management: When asked "next best step" after positive tap test in an appropriate candidate, the answer is referral to neurosurgery for ventriculoperitoneal shunt evaluation. Do not order more imaging or empiric medications. When the candidate is poor (severe dementia, bedbound, advanced comorbid Alzheimer pathology), the right answer shifts to supportive care, PT, fall prevention, and goals-of-care discussion — recognize that not shunting is sometimes the correct exam answer.

Pharmacotherapy and Non-Surgical Management

— Occasionally used off-label as a temporizing measure (reduces CSF production via carbonic anhydrase inhibition).

— Evidence weak; not a substitute for shunting.

— Dose 250–500 mg/day; monitor for metabolic acidosis, hypokalemia, paresthesias, nephrolithiasis.

— Reasonable bridge in patients awaiting surgery or with surgical contraindications — but do not select this as definitive therapy on the exam.

— Repeated large-volume taps every few weeks can provide transient symptomatic relief.

— Used when surgery is declined or contraindicated; not a long-term strategy due to infection risk and inconvenience.

— Urinary urgency/incontinence: Avoid anticholinergics (oxybutynin, tolterodine) in elderly — worsen cognition. Prefer mirabegron (β3-agonist) if pharmacotherapy needed; first-line is timed voiding and pelvic floor PT.

— Depression/apathy: SSRIs (sertraline, escitalopram) if comorbid depression contributing to functional decline.

— Sleep: Treat OSA, avoid benzodiazepines and Z-drugs.

— Stop or minimize anticholinergics, opioids, benzodiazepines, antipsychotics, muscle relaxants, antihistamines — all worsen gait and cognition.

— Use the Beers Criteria to systematically review medications in older adults.

— Physical therapy for gait training, balance, fall prevention.

— Occupational therapy for ADLs, home safety evaluation.

— Home modifications: remove rugs, install grab bars, ensure adequate lighting.

— Vitamin D supplementation and exercise program for fall reduction.

Core principle: NPH has no effective pharmacotherapy. Definitive treatment is CSF diversion (shunting). Medications target comorbidities, mimics, and symptom support.

Acetazolamide:

Serial lumbar punctures:

Symptomatic and adjunctive medications:

Deprescribing review (Step 3 favorite):

Non-pharmacologic management:

Board pearl: If the answer choices include "start donepezil" or "start memantine" for a patient with clear NPH and pending shunt evaluation, do not pick them — those are for Alzheimer disease. The high-yield answer for medical optimization while awaiting shunt is deprescribe anticholinergics and refer to PT.

Procedural Management — Ventriculoperitoneal Shunt and Alternatives

— Catheter from lateral ventricle to peritoneal cavity via a programmable valve.

— Programmable (adjustable) valves preferred — allow noninvasive pressure adjustment to balance underdrainage vs overdrainage.

— Antisiphon devices reduce overdrainage when upright.

— Ventriculoatrial (VA) shunt: used when abdomen unsuitable (prior surgery, peritonitis, obesity); higher risk of endocarditis, shunt nephritis, pulmonary embolism.

— Lumboperitoneal (LP) shunt: less common in US for iNPH; risk of acquired Chiari, scoliosis.

— Reserved primarily for obstructive (non-communicating) hydrocephalus (e.g., aqueductal stenosis). Generally not first-line for iNPH, though selected cases respond.

— Hold anticoagulants and antiplatelets per surgical protocol; bridge if high thrombotic risk (mechanical valve, recent VTE).

— Verify imaging recent (<3 months).

— Antibiotic prophylaxis (typically cefazolin) within 60 min of incision; antibiotic-impregnated catheters reduce infection risk.

— DVT prophylaxis post-op once hemostasis confirmed (mechanical first, then pharmacologic).

— Baseline post-op CT to confirm catheter position and exclude hemorrhage.

— Monitor for headache (overdrainage), fever (infection), new focal deficits (subdural).

— Valve programming: start at moderate pressure; adjust based on symptoms and imaging over weeks.

— Gait improvement 60–80% in well-selected patients, often within days to weeks.

— Cognitive improvement 30–50%, more variable and slower.

— Continence improvement least predictable.

— Durability of improvement at 1 year ~70%; at 3 years ~50–60% with appropriate management.

Ventriculoperitoneal (VP) shunt — gold standard:

Alternative shunts:

Endoscopic third ventriculostomy (ETV):

Perioperative management (Step 3 / CCS):

Postoperative course:

Expected outcomes:

CCS pearl: After positive tap test → neurosurgery consult → VP shunt with programmable valve → post-op CT head → physical therapy → outpatient follow-up at 2 weeks with valve adjustment as needed. Order the sequence — exam credit is for the chain, not any single step.

Special Populations — Elderly, Renal, and Hepatic Considerations

— Median age at shunting is 70–75; most patients have multiple comorbidities.

— Comprehensive geriatric assessment before surgery: cognition, mobility, nutrition, social support, advance directives.

— Frailty index (e.g., Clinical Frailty Scale ≥6) predicts poor surgical outcome; consider non-operative path.

— Polypharmacy review: Beers Criteria — stop anticholinergics, benzodiazepines, sedating antihistamines; reassess opioids and gabapentinoids.

— Fall risk: even before shunt, initiate PT, vitamin D ≥800 IU/day, home safety evaluation, and consider hip protectors in high-risk patients.

— Delirium risk post-op: minimize tethers, treat pain non-opioid-first, early mobilization, orient frequently.

— Acetazolamide accumulates in CKD and worsens metabolic acidosis — avoid if eGFR <30 or use reduced dose with monitoring.

— Contrast imaging: prefer non-contrast MRI; if gadolinium needed, avoid linear agents in advanced CKD due to nephrogenic systemic fibrosis risk.

— Adjust perioperative antibiotics (cefazolin, vancomycin) for CrCl.

— Anesthesia and sedation considerations — reduce benzodiazepines, use shorter-acting agents.

— Coagulopathy from cirrhosis increases bleeding risk; correct INR with vitamin K and consider platelet transfusion if <50K pre-op.

— Ascites is a relative contraindication to VP shunt (peritoneal absorption impaired, infection risk) — consider VA shunt instead.

— Active heart failure, severe valvular disease → optimize before surgery.

— Anticoagulation for AF: hold per ACC/AHA perioperative guidance; bridging usually not required for low-risk AF.

Elderly (the modal NPH patient):

Renal impairment:

Hepatic impairment:

Cardiac comorbidity:

Step 3 management: A 78-year-old with iNPH, CKD stage 4, and ascites from cirrhosis is not a good VP shunt candidate. The correct sequence is: medical optimization, deprescribing, PT, fall prevention, palliative-leaning goals discussion, and consideration of VA shunt only after multidisciplinary review if symptoms severe and life expectancy reasonable.

Special Populations — Younger Adults and Secondary NPH

— In children, hydrocephalus is usually obstructive (aqueductal stenosis, Chiari malformation, posterior fossa tumors, post-IVH in preemies) — presents with macrocephaly, sunset eyes, bulging fontanelle, vomiting, and is treated with VP shunt or ETV depending on cause.

— iNPH is fundamentally a disease of older adults; suspecting iNPH in a 30-year-old is almost always wrong.

— Post-subarachnoid hemorrhage: Most common cause — develops weeks to months after SAH due to arachnoid granulation scarring. Routine outpatient follow-up after SAH should include gait and cognitive screening at 3 and 6 months.

— Post-meningitis (bacterial, TB, fungal): chronic inflammation impairs CSF absorption.

— Post-traumatic brain injury: consider in TBI survivors with subacute cognitive/gait decline.

— Post–intracranial surgery or radiation: rare but recognized.

— These patients often have higher shunt-response rates than iNPH.

— iNPH in pregnancy is exceedingly rare; pre-existing shunts (e.g., from prior pediatric hydrocephalus) generally tolerate pregnancy well.

— Shunt malfunction risk rises with rising intra-abdominal pressure in third trimester — coordinate with neurosurgery.

— Mode of delivery is driven by obstetric indications; shunt is not itself an indication for cesarean.

— Avoid teratogenic medications; acetazolamide is category C and generally avoided in first trimester.

— Wilson disease, Huntington disease, autoimmune encephalitis, HIV-associated neurocognitive disorder, CADASIL, neurosyphilis, prion disease.

— A "young patient with ventriculomegaly" should prompt search for aqueductal stenosis on MRI cine flow before labeling as NPH.

Pediatric and young-adult hydrocephalus is not iNPH:

Secondary NPH in middle-aged adults:

Pregnancy:

Younger-onset dementia mimics to exclude:

Key distinction: iNPH = older adult, gait-first, communicating, normal opening pressure; obstructive hydrocephalus = any age, often headache/vomiting, MRI shows obstruction, treated with ETV or shunt depending on level. Mixing these up is a common exam trap.

Complications and Adverse Outcomes

— Progressive functional decline: falls, fractures (hip, wrist, vertebral), loss of independence, nursing home placement.

— Skin breakdown and UTIs from incontinence.

— Caregiver burnout and depression.

— Aspiration in late stages with severe cognitive impairment.

— Subdural hematoma / hygroma (5–15%): from overdrainage, especially in older adults with brain atrophy. Presents with new headache, worsening gait, focal deficits, or declining cognition after initial improvement. Order non-contrast CT head.

— Shunt infection (3–10%): fever, meningismus, valve-site erythema, CSF pleocytosis. Most common organisms: coagulase-negative staph, S. aureus, gram-negatives. Treatment: shunt externalization or removal + IV antibiotics, replace once CSF sterile.

— Shunt malfunction/obstruction: Recurrence of original symptoms (gait decline, incontinence, cognitive worsening). Shunt series (skull, chest, abdomen X-rays) + CT head to evaluate.

— Overdrainage syndrome: Orthostatic headache, nausea — adjust valve pressure upward.

— Seizures (post-op, ~3–5%).

— Abdominal complications: catheter migration, pseudocyst, peritonitis, bowel perforation (rare).

— VA shunt-specific: endocarditis, shunt nephritis (immune-complex glomerulonephritis), pulmonary embolism.

— Delirium, ileus, DVT, atelectasis, MI in high-risk patients.

— ~20–40% of shunted patients have suboptimal response — often due to misdiagnosis (coexisting Alzheimer, vascular dementia), advanced disease, or shunt malfunction.

— Always revisit the diagnosis before assuming refractoriness.

Untreated NPH complications:

Shunt-related complications (cumulative ~20–40% at 5 years):

Anesthesia and perioperative complications:

Failure to improve after shunting:

CCS pearl: A shunted NPH patient presenting weeks to months later with new headache and recurrent gait decline → order non-contrast CT head FIRST to evaluate for subdural hematoma. If imaging is clean and shunt looks intact, consider shunt malfunction (shunt series, neurosurgery consult) or overdrainage (valve adjustment). Do not just reassure and discharge.

When to Escalate Care — Consults and Inpatient Triage

— Primary care suspicion → neurology referral for cognitive/gait workup and tap test coordination.

— Positive tap test → neurosurgery referral for shunt evaluation.

— Consider geriatrics for comprehensive assessment, PT/OT, social work.

— Acute deterioration in a known NPH patient or shunted patient — rule out subdural hematoma, shunt infection, shunt malfunction.

— Headache + vomiting + papilledema — suggests acute hydrocephalus or shunt failure with raised ICP, not classic iNPH.

— New focal neurologic deficit.

— Suspected shunt infection (fever, meningismus, valve erythema).

— Suspected shunt infection → admit, blood/CSF cultures, empiric vancomycin + cefepime (or ceftriaxone) pending sensitivities, neurosurgery consult for externalization.

— Subdural hematoma with mass effect or neurologic decline.

— Falls with significant injury (hip fracture, head trauma).

— Delirium with safety concerns at home.

— Planned extended lumbar drainage for diagnostic confirmation.

— Required for post-op shunt patients with new altered mental status, seizures, hemodynamic instability, or suspected intracranial hemorrhage requiring close neuro checks.

— Severe shunt infection with sepsis, ventriculitis.

— Neurology, neurosurgery, geriatrics, PT/OT, urology (refractory incontinence), social work, palliative care for non-surgical candidates.

Outpatient pathway (most NPH evaluations):

Indications for urgent neurology/neurosurgery consultation:

Indications for inpatient admission:

ICU triage:

Multidisciplinary team:

Step 3 management: A shunted NPH patient brought to the ED with fever, neck stiffness, and altered mental status → admit, blood cultures × 2, LP if safe (consider tapping the shunt reservoir), empiric vancomycin + cefepime, neurosurgery consult for likely shunt externalization. Do not delay antibiotics for imaging — the sequence is cultures → empiric antibiotics → imaging → source control.

Key Differentials — Other Dementias

— Memory loss precedes gait disturbance, opposite of NPH.

— MRI: hippocampal/mesial temporal atrophy, generalized cortical atrophy with proportionate ventricular enlargement (ex vacuo).

— MMSE/MoCA show prominent memory and visuospatial deficits; cueing does not help (encoding failure).

— May coexist with NPH (~30% overlap) — limits shunt response.

— Stepwise decline, focal neurologic findings, hypertension/diabetes/AF history.

— MRI: extensive white matter disease, lacunes, cortical infarcts.

— Gait can mimic NPH (lower-body parkinsonism), but focal deficits and stroke risk factors point the way.

— Fluctuating cognition, visual hallucinations, REM sleep behavior disorder, parkinsonism.

— Severe neuroleptic sensitivity — antipsychotics cause marked worsening.

— DAT scan abnormal.

— Younger onset (50s–60s), personality/behavior change or progressive aphasia dominate.

— MRI: frontal/temporal atrophy disproportionate to ventricles.

— Rapidly progressive dementia (weeks to months), myoclonus, ataxia.

— EEG periodic sharp waves, CSF 14-3-3 and RT-QuIC positive, MRI cortical ribboning.

— Apathy, poor effort on testing, prominent neurovegetative symptoms.

— Improves with treatment of depression; trial SSRI if uncertain.

Alzheimer disease (AD):

Vascular dementia:

Dementia with Lewy bodies (DLB):

Frontotemporal dementia (FTD):

Creutzfeldt-Jakob disease:

Pseudodementia of depression:

Key distinction: All dementias can produce some gait change late, but only NPH has gait-first, magnetic, broad-based shuffling out of proportion to cognitive loss, with disproportionate ventriculomegaly on MRI and normal opening pressure. Anchor on the temporal sequence of symptoms and the ratio of ventricles to sulci on imaging.

Key Differentials — Other-Category Causes

— Resting tremor, cogwheel rigidity, bradykinesia, shuffling but narrow-based gait, stooped posture, reduced arm swing.

— Response to levodopa is diagnostic and therapeutic; NPH does not respond.

— DAT scan abnormal in PD, normal in NPH.

— Early falls (backward), vertical gaze palsy, axial rigidity, pseudobulbar affect.

— MRI: midbrain "hummingbird" sign.

— No response to levodopa or shunting.

— Autonomic failure (orthostatic hypotension, urinary retention), cerebellar or parkinsonian features.

— MRI: pontine "hot cross bun" sign, cerebellar atrophy.

— Spastic gait, hyperreflexia, Hoffmann sign, sensory level, urinary urgency.

— MRI cervical spine shows cord compression — always image the cervical spine in gait disorders before attributing to NPH.

— Sensory ataxia, paresthesias, Romberg, megaloblastic anemia.

— Check B12 in every dementia/gait workup.

— Tabes dorsalis, Argyll Robertson pupils, general paresis. Check RPR.

— Hydrocephalus ex vacuo (ventricular enlargement from brain atrophy) — proportionate sulcal enlargement, no transependymal flow, no DESH.

— Obstructive hydrocephalus — aqueductal stenosis, posterior fossa mass, colloid cyst of third ventricle — managed differently (often ETV).

— Anticholinergics, benzodiazepines, opioids, sedating antihistamines, antipsychotics — always review the med list before invasive workup.

Parkinson disease (PD):

Progressive supranuclear palsy (PSP):

Multiple system atrophy (MSA):

Cervical spondylotic myelopathy:

B12 deficiency / subacute combined degeneration:

Neurosyphilis:

Normal-pressure hydrocephalus mimics on imaging:

Medication-induced gait/cognitive decline:

Board pearl: Before attributing gait disorder to NPH, always exclude cervical myelopathy with cervical spine MRI if exam shows hyperreflexia or Babinski, and always exclude PD with a careful exam for tremor, rigidity, and bradykinesia. Missing either is a classic exam pitfall.

Post-Shunt Long-Term Plan and Secondary Prevention

— Acetaminophen scheduled for incisional pain; minimize opioids.

— DVT prophylaxis (mechanical first, then enoxaparin once neurosurgery clears at 24–48 h).

— Resume home antihypertensives as tolerated; avoid hypotension to prevent overdrainage symptoms.

— Resume statin, antiplatelet, anticoagulation per neurosurgery clearance (typically antiplatelet ~24–48 h, anticoagulation later depending on bleeding risk).

— Stool softener to prevent Valsalva.

— MRI safety: Most modern programmable valves are MRI conditional but may require reprogramming after MRI — patient should carry valve identification card and notify radiology/neurosurgery before any MRI.

— Antibiotic prophylaxis is not routinely required for dental procedures with VP shunts (differs from VA shunts where some experts recommend it).

— Fall prevention: PT, home safety eval, vitamin D, vision/hearing optimization, footwear review.

— Cardiovascular risk: Control BP (<130/80 in most older adults per ACC/AHA, individualized), statin if ASCVD risk warrants, manage AF anticoagulation.

— Diabetes: HbA1c goal individualized (7.5–8% in many older adults per ADA).

— Vaccinations: annual influenza, pneumococcal (PCV20 or PCV15+PPSV23), RSV ≥60, shingles, COVID boosters.

— Cognitive engagement, exercise, Mediterranean-style diet for general brain health.

— Deprescribe anticholinergics and other gait-impairing agents.

— Connect to local Area Agency on Aging, caregiver support groups, Alzheimer's/dementia organizations (many cover NPH).

— Address advance directives, healthcare proxy, POLST/MOLST.

Post-shunt discharge medications and orders:

Shunt-specific long-term issues:

Secondary prevention pillars:

Caregiver and social support:

Step 3 management: At the 2-week post-op visit, assess incision, check gait (TUG, 10-meter walk), screen for headache (overdrainage) and confusion (subdural), confirm valve settings, review medications, and arrange PT continuation. Schedule 3-month and 6-month follow-ups with neurosurgery and neurology, plus annual primary care visits emphasizing falls, vaccines, and goals of care.

Follow-Up, Monitoring, and Rehabilitation

— 2 weeks: wound check, valve setting, gait reassessment, screen for overdrainage (orthostatic headache).

— 1 month: repeat TUG, 10-meter walk, MoCA — compare to pre-op baseline.

— 3 and 6 months: continued functional reassessment; consider valve adjustment if response suboptimal.

— Annually thereafter: gait, cognition, continence; surveillance for shunt malfunction or coexisting AD/vascular dementia.

— Gait speed (>0.8 m/s associated with community ambulation).

— TUG (<13.5 s = lower fall risk).

— MoCA trajectory.

— Caregiver-reported continence, falls, ADLs (e.g., Katz ADL, Lawton IADL).

— Physical therapy focusing on gait, balance, strength, dual-task training; typically 6–12 weeks post-op, longer if needed.

— Occupational therapy for ADLs and home modifications.

— Speech therapy if cognitive-communication or swallowing issues.

— Pelvic floor physical therapy for urinary symptoms.

— Set realistic expectations: gait often improves within days–weeks; cognition slower and less complete; continence variable.

— Educate on warning signs requiring urgent evaluation:

— New or worsening headache (especially orthostatic).

— Fever, redness along shunt tract, neck stiffness.

— Sudden cognitive or gait decline after initial improvement.

— Seizures, focal weakness, vomiting.

— Patient should carry shunt/valve identification card.

— Assess fitness to drive at each visit; refer for formal driving evaluation if cognition or reaction time is borderline. Mandatory reporting laws vary by state — know your state's requirements.

— If response plateaus or declines, re-evaluate for coexisting Alzheimer or vascular dementia, shunt malfunction, subdural hematoma, or medication effect.

Follow-up cadence after shunting:

Objective monitoring metrics:

Rehabilitation program:

Counseling points:

Driving:

Coexisting condition surveillance:

CCS pearl: Schedule PT consult, home safety evaluation, 2-week wound check, and 1-month gait reassessment as standing orders on discharge — these are commonly missed steps that earn credit on CCS cases and reflect real-world Step 3 care.

Ethical, Legal, and Patient Safety Considerations

— Assess decision-making capacity specific to the shunt decision: can the patient understand, appreciate, reason, and express a choice?

— Capacity is decision-specific and can fluctuate — mild cognitive impairment does not automatically eliminate capacity.

— If the patient lacks capacity, identify the healthcare proxy/surrogate; in absence, follow state hierarchy (spouse → adult children → parents → siblings).

— Always involve the patient in discussion to the extent possible; document assent even when surrogate consents.

— Use the evaluation as an opportunity to address advance directives, healthcare proxy, POLST/MOLST, and code status.

— In poor surgical candidates (severe dementia, frailty, advanced comorbidity), explicitly discuss palliative-leaning approach — recommending against surgery is a legitimate, evidence-based decision.

— Cognitive impairment and gait disorder both impair driving. Several states mandate physician reporting of dementia or impaired drivers to the DMV (California, Oregon, Pennsylvania, others); most states permit but do not require reporting.

— Document the conversation, recommend cessation or formal driving evaluation, and report per state law.

— Untreated NPH is a major fall risk; failure to address fall prevention can constitute negligence.

— Screen for elder abuse and neglect — incontinence, mobility loss, and cognitive impairment increase vulnerability; mandatory reporting to Adult Protective Services applies in all states for suspected abuse.

— Post-shunt discharge is a high-risk transition: medication reconciliation, valve card in hand, written warning signs, scheduled follow-ups, and direct communication with primary care.

— Failure to communicate valve type/setting to outpatient clinicians is a common safety event — include it in the discharge summary.

— Discuss enrollment in NPH registries or trials when appropriate; obtain separate research consent.

— Recognize disparities in access to neurosurgical care; advocate for referral when indicated regardless of payer status.

Informed consent for shunt surgery in cognitively impaired patients:

Goals of care and advance directives:

Driving safety and mandatory reporting:

Falls and elder safety:

Transitions of care (Step 3 favorite):

Research and equity:

Step 3 management: When a daughter requests "do everything" for a severely demented, bedbound, frail parent with NPH, the correct approach is a structured family meeting clarifying realistic outcomes, exploring patient's previously expressed wishes, and offering comfort-focused care as a valid option — not automatically proceeding to surgery.

High-Yield Associations and Rapid-Fire Clinical Facts

Triad mnemonic: "Wet, wobbly, wacky" = urinary incontinence, gait apraxia, dementia. Gait first, cognition last.

Hakim–Adams syndrome = eponym for NPH triad (1965).

Opening pressure on LP: 70–245 mm H₂O (normal) — the "normal pressure" of NPH.

Evans index: frontal horn width ÷ inner skull diameter; >0.3 = ventriculomegaly.

Callosal angle <90° on coronal MRI = supports iNPH.

DESH: Disproportionately Enlarged Subarachnoid space Hydrocephalus — tight high convexities + widened Sylvian fissures.

Tap test: remove 30–50 mL CSF, reassess gait at 2–24 h; positive response predicts shunt benefit.

Extended lumbar drainage: 3–5 days, higher sensitivity than single tap.

Treatment: Ventriculoperitoneal shunt with programmable valve.

Shunt response: gait > cognition > continence in likelihood and speed of improvement.

Best predictors of shunt response: gait-dominant presentation, short duration, positive tap test, secondary NPH (post-SAH).

Worst predictors: severe dementia, long duration, coexisting Alzheimer pathology, extensive white matter disease.

Most feared shunt complication in elderly: subdural hematoma from overdrainage.

Most common shunt infection organisms: coagulase-negative staphylococci, then S. aureus.

VA shunt-specific complications: endocarditis, shunt nephritis (immune-complex GN), PE.

Programmable valves: may need reprogramming after MRI — always check.

Gait pattern: magnetic, broad-based, short-stepped, en-bloc turns — preserved arm swing distinguishes from PD.

Urinary pattern: urgency → frequency → frank incontinence with frontal indifference.

Cognitive pattern: frontal-subcortical — slow processing, executive dysfunction, apathy; memory storage relatively preserved early.

iNPH coexists with Alzheimer disease in up to 30% — limits but does not preclude shunt response.

Key mimics: Alzheimer (memory first), Parkinson (tremor, levodopa response), vascular dementia (stepwise, focal deficits), cervical myelopathy (hyperreflexia, sensory level), B12 deficiency.

Board pearl: If a Step 3 stem says "older adult with ventriculomegaly, gait disturbance, mild cognitive impairment, urinary urgency, normal opening pressure" → answer is large-volume LP (tap test) as the next best diagnostic step, and VP shunt as definitive treatment if tap is positive.

Board Question Stem Patterns

— 74-year-old man, 8-month gait disturbance, recent urinary urgency, family notes slowed thinking. Exam: magnetic gait, normal strength. MRI: ventriculomegaly, Evans 0.34, tight high convexities.

— Best next step? → Large-volume lumbar puncture (tap test) with pre/post gait assessment.

— Definitive treatment? → Ventriculoperitoneal shunt.

— Older adult with gait shuffling and mild memory loss. Has resting tremor and cogwheel rigidity.

— Diagnosis: Parkinson disease — not NPH. Next step: trial of levodopa-carbidopa.

— Gait disorder, urinary urgency, but exam shows hyperreflexia, Hoffmann sign, sensory level.

— Next step: MRI cervical spine, not brain.

— Shunted NPH patient, 6 weeks post-op, presents with new headache, worsening gait, mild confusion.

— Next step: Non-contrast CT head to evaluate for subdural hematoma.

— 3 weeks post-shunt: fever, neck stiffness, valve-site erythema.

— Management: Blood cultures, CSF studies (consider shunt reservoir tap), empiric vancomycin + cefepime, neurosurgery consult for externalization.

— Patient with NPH features but prominent early memory loss and hippocampal atrophy on MRI.

— Counseling: Shunt may still help gait, but expect limited cognitive improvement; consider amyloid biomarkers before surgery.

— Severely demented, bedbound, frail patient with NPH features.

— Best answer: Supportive care, PT, fall prevention, goals-of-care discussion — not shunt.

— Older patient with proportionate ventricular and sulcal enlargement ("ex vacuo") and Alzheimer-pattern atrophy.

— Diagnosis: Alzheimer disease with hydrocephalus ex vacuo — not NPH, do not shunt.

— Patient 4 months after aneurysmal SAH develops gait + cognitive decline.

— Diagnosis: post-SAH (secondary) NPH; high shunt response rate — proceed with workup.

— Patient with mild NPH features also on oxybutynin, diphenhydramine PRN, lorazepam.

— Best initial step: Deprescribe anticholinergics and sedatives, reassess before invasive testing.

Stem 1 — Classic triad recognition:

Stem 2 — Differential trap:

Stem 3 — Cervical myelopathy mimic:

Stem 4 — Post-shunt complication:

Stem 5 — Shunt infection:

Stem 6 — Coexisting Alzheimer:

Stem 7 — Poor surgical candidate:

Stem 8 — Imaging pitfall:

Stem 9 — Secondary NPH:

Stem 10 — Medication review:

Board pearl: Step 3 stems reward the stepwise pathway: recognize triad → MRI → exclude mimics → tap test → neurosurgery referral → shunt → structured follow-up. Skipping steps or going directly to surgery is almost always wrong.

One-Line Recap

One-liner: Normal pressure hydrocephalus is a potentially reversible communicating hydrocephalus of older adults defined by the Hakim–Adams triad of gait apraxia, urinary incontinence, and frontal-subcortical cognitive impairment with ventriculomegaly disproportionate to atrophy and normal CSF opening pressure, diagnosed clinically and confirmed with a large-volume tap test, and treated definitively with a ventriculoperitoneal shunt in well-selected patients.

Triad: wet (urinary incontinence with frontal indifference), wobbly (magnetic, broad-based gait — first to appear, first to improve), wacky (frontal-subcortical dementia — last to appear, least to improve).

Diagnose: MRI showing Evans index >0.3, callosal angle <90°, DESH pattern, then lumbar puncture with normal opening pressure (70–245 mm H₂O) and large-volume tap test (30–50 mL) with pre- and post-tap TUG and gait speed; consider extended lumbar drainage if single tap negative but suspicion high.

Treat: Ventriculoperitoneal shunt with programmable valve for appropriate candidates (gait-dominant, short duration, positive tap, limited Alzheimer overlap); best predictor of benefit is gait response to tap; expected outcome is gait > cognition > continence improvement.

Watch for and prevent: Subdural hematoma (overdrainage), shunt infection (coag-neg staph; vancomycin + cefepime, externalize), shunt malfunction (recurrence of symptoms — shunt series + CT), valve reprogramming after MRI; structure follow-up at 2 weeks, 1 month, 3 and 6 months, with PT, fall prevention, medication deprescribing, vaccinations, and goals-of-care conversations, and always revisit the diagnosis (Alzheimer, vascular, PD, cervical myelopathy) when response is poor.

Step 3 management: Recognize the triad early in any outpatient dementia evaluation — gait-first dementia in an older adult mandates an MRI and, if ventriculomegaly is disproportionate, a tap test before committing to a diagnosis of irreversible dementia.