Normal Pressure Hydrocephalus

DIAGNOSIS: Normal Pressure Hydrocephalus (NPH) ICD-10: G91.2 (Normal pressure hydrocephalus); G91.0 (Communicating hydrocephalus); R41.0 (Disorientation, unspecified); R26.0 (Ataxic gait); R32 (Unspecified urinary incontinence)

CPT CODES: 85025 (CBC with differential), 80048 (BMP), 85610 (Coagulation panel - PT/INR, PTT), 85730 (Coagulation panel - PT/INR, PTT), 84443 (TSH), 82607 (Vitamin B12), 81001 (Urinalysis with culture), 87086 (Urinalysis with culture), 83036 (Hemoglobin A1c), 82746 (Folate), 86592 (RPR or VDRL), 86701 (HIV antibody), 85652 (ESR, CRP), 86140 (ESR, CRP), 80076 (Hepatic panel), 84153 (PSA - males), 86255 (Paraneoplastic antibody panel), 86235 (Anti-neuronal antibodies - NMDA-R, LGI1, CASPR2), 81405 (Genetic testing for APP, PSEN1, PSEN2), 70551 (MRI Brain without contrast), 70450 (CT Head non-contrast), 70553 (MRI Brain with volumetric analysis), 76390 (MR spectroscopy), 78816 (FDG-PET Brain), 61210 (Intracranial pressure monitoring - continuous), 62270 (Infusion testing - CSF outflow resistance), 78630 (Radionuclide cisternography), 89051 (Cell count - tubes 1 and 4), 84157 (Protein), 82947 (Glucose with serum glucose), 83519 (CSF Abeta-42, total tau, p-tau) SYNONYMS: NPH, idiopathic NPH (iNPH), Hakim-Adams syndrome, communicating hydrocephalus, chronic hydrocephalus, occult hydrocephalus, adult-onset hydrocephalus, secondary NPH, low-pressure hydrocephalus SCOPE: Comprehensive evaluation of suspected NPH, diagnostic workup including high-volume lumbar puncture (tap test), prediction of shunt responsiveness, neurosurgical referral, and post-shunt monitoring. Covers idiopathic NPH (most common) and secondary NPH. Does not cover acute obstructive hydrocephalus or pediatric hydrocephalus.

VERSION: 1.1 CREATED: January 27, 2026 REVISED: January 30, 2026

STATUS: Approved

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PRIORITY KEY: STAT = Immediate | URGENT = Within hours | ROUTINE = Standard | EXT = Extended/atypical cases | - = Not applicable to this setting

CLINICAL PEARL: The classic triad of NPH is "wet, wacky, wobbly" - urinary incontinence, cognitive impairment, and gait disturbance. Gait is typically the first and most prominent symptom, and responds best to shunt surgery. The presence of all three symptoms is not required for diagnosis.

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SECTION A: ACTION ITEMS

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1. LABORATORY WORKUP

1A. Essential/Core Labs

Test (CPT)	ED	HOSP	OPD	ICU	Rationale	Target Finding
CBC with differential (85025)	STAT	ROUTINE	ROUTINE	-	Pre-surgical screening; rule out infection	Normal
BMP (80048)	STAT	ROUTINE	ROUTINE	-	Electrolyte assessment; pre-surgical renal function	Normal electrolytes, BUN, Cr
Coagulation panel - PT/INR, PTT (85610, 85730)	STAT	ROUTINE	ROUTINE	-	Pre-procedural assessment for LP and surgery	INR <1.5, PTT <40
TSH (84443)	-	ROUTINE	ROUTINE	-	Hypothyroidism can cause cognitive impairment	0.4-4.0 mIU/L
Vitamin B12 (82607)	-	ROUTINE	ROUTINE	-	B12 deficiency causes reversible dementia and gait ataxia	>300 pg/mL
Urinalysis with culture (81001, 87086)	STAT	ROUTINE	ROUTINE	-	Rule out UTI as cause of incontinence or confusion	Negative for infection
Hemoglobin A1c (83036)	-	ROUTINE	ROUTINE	-	Diabetes contributes to small vessel disease and neuropathy	<7%

1B. Extended Workup (Second-line)

Test (CPT)	ED	HOSP	OPD	ICU	Rationale	Target Finding
Folate (82746)	-	ROUTINE	ROUTINE	-	Deficiency contributes to cognitive impairment	>3 ng/mL
RPR or VDRL (86592)	-	ROUTINE	ROUTINE	-	Neurosyphilis can cause dementia and gait abnormalities	Nonreactive
HIV antibody (86701)	-	ROUTINE	ROUTINE	-	HIV-associated neurocognitive disorder in at-risk patients	Negative
ESR, CRP (85652, 86140)	STAT	ROUTINE	ROUTINE	-	Inflammatory or infectious causes of meningitis/encephalitis	Normal
Hepatic panel (80076)	-	ROUTINE	ROUTINE	-	Hepatic encephalopathy in patients with liver disease	Normal
PSA - males (84153)	-	-	ROUTINE	-	Prostate disease contributing to urinary symptoms	Normal for age

1C. Rare/Specialized (Refractory or Atypical)

Test (CPT)	ED	HOSP	OPD	ICU	Rationale	Target Finding
Paraneoplastic antibody panel (86255)	-	EXT	EXT	-	Autoimmune etiology if subacute presentation	Negative
Anti-neuronal antibodies - NMDA-R, LGI1, CASPR2 (86235)	-	EXT	EXT	-	Autoimmune encephalitis causing cognitive/behavioral changes	Negative
Genetic testing for APP, PSEN1, PSEN2 (81405)	-	-	EXT	-	Early-onset dementia with family history	No pathogenic variants

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2. DIAGNOSTIC IMAGING & STUDIES

2A. Essential/First-line

Study (CPT)	ED	HOSP	OPD	ICU	Timing	Target Finding	Contraindications
MRI Brain without contrast (70551)	URGENT	ROUTINE	ROUTINE	-	Initial evaluation	Ventriculomegaly with Evans index >0.3; callosal angle <90 degrees; DESH pattern; periventricular edema (transependymal flow); absence of cortical atrophy proportionate to ventricular size	MRI-incompatible devices; claustrophobia
CT Head non-contrast (70450)	STAT	STAT	ROUTINE	-	If MRI unavailable or emergent presentation	Ventriculomegaly out of proportion to sulcal enlargement; Evans index >0.3	Pregnancy (relative)

2B. Extended

Study (CPT)	ED	HOSP	OPD	ICU	Timing	Target Finding	Contraindications
MRI Brain with volumetric analysis (70553)	-	-	ROUTINE	-	Detailed assessment	Quantify ventricular volume; hippocampal volume preservation (unlike AD); tight high-convexity sulci	MRI contraindications
MRI with CSF flow study - phase-contrast (70553)	-	-	ROUTINE	-	Assess aqueductal CSF flow	Hyperdynamic aqueductal flow; increased stroke volume (>42 microL)	MRI contraindications
MR spectroscopy (76390)	-	-	EXT	-	Atypical cases to differentiate from AD	Normal NAA/Cr ratio (reduced in AD); no significant metabolic abnormality	MRI contraindications
FDG-PET Brain (78816)	-	-	EXT	-	Differentiate NPH from AD or FTD	Preserved metabolism (unlike AD temporoparietal hypometabolism)	None

2C. Rare/Specialized

Study (CPT)	ED	HOSP	OPD	ICU	Timing	Target Finding	Contraindications
Intracranial pressure monitoring - continuous (61210)	-	EXT	-	-	Diagnostic uncertainty after tap test	B-waves present (indicates impaired CSF dynamics)	Coagulopathy; skin infection
Infusion testing - CSF outflow resistance (62270)	-	EXT	EXT	-	Research settings; predict shunt response	Elevated Rout >12-18 mmHg/mL/min suggests shunt responsiveness	Coagulopathy
Radionuclide cisternography (78630)	-	-	EXT	-	Rarely used; assesses CSF flow patterns	Delayed clearance over convexities; ventricular reflux	None

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LUMBAR PUNCTURE

Indication: Diagnostic and prognostic - high-volume lumbar puncture ("tap test") to assess for clinical improvement predicting shunt responsiveness Timing: ROUTINE during outpatient evaluation; can be done in hospital if inpatient Volume Required: 30-50 mL (high-volume therapeutic tap) - remove CSF until opening pressure is halved or symptoms of low pressure develop

Study (CPT)	ED	HOSP	OPD	ICU	Rationale	Target Finding
Opening pressure (62270)	URGENT	ROUTINE	ROUTINE	-	Confirm normal or mildly elevated pressure in NPH	5-18 cm H2O (typically normal or low-normal in NPH)
Cell count - tubes 1 and 4 (89051)	URGENT	ROUTINE	ROUTINE	-	Rule out infection or inflammation	WBC <5, RBC 0
Protein (84157)	URGENT	ROUTINE	ROUTINE	-	Rule out infectious/inflammatory causes	Normal 15-45 mg/dL
Glucose with serum glucose (82947)	URGENT	ROUTINE	ROUTINE	-	Rule out infectious meningitis	>60% of serum glucose
CSF Abeta-42, total tau, p-tau (83519)	-	ROUTINE	ROUTINE	-	Differentiate from Alzheimer's disease (optional)	Normal in NPH; low Abeta-42 with high tau in AD

Tap Test Protocol: 1. Record baseline gait assessment (timed 10-meter walk, steps to walk 10 meters, Tinetti gait score) 2. Record baseline cognitive testing (MoCA or MMSE) 3. Remove 30-50 mL CSF 4. Repeat gait assessment at 30 min, 4 hours, 24 hours, and 72 hours post-LP 5. Repeat cognitive testing at 24-72 hours 6. Positive tap test: Improvement in gait (>20% faster walk time or >10% fewer steps) predicts shunt response

Special Handling: Standard CSF handling; freeze sample if sending for biomarkers Contraindications: Coagulopathy (INR >1.5, platelets <50k); posterior fossa mass; skin infection at site; anticoagulation (hold appropriately)

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EXTENDED LUMBAR DRAIN TRIAL

Indication: Diagnostic uncertainty after single tap test; equivocal tap test results; more sensitive predictor of shunt response Setting: Inpatient (requires admission for continuous drainage and monitoring)

Component	Protocol	Target	ED	HOSP	OPD	ICU
Lumbar drain placement	Neurosurgery places external lumbar drain	Secure placement	-	ROUTINE	-	-
CSF drainage rate	10-15 mL/hour continuously for 3-5 days	Drain 200-400 mL/day	-	ROUTINE	-	-
Serial gait assessment	Daily timed walk and Tinetti score	>30% improvement in walk time or gait score	-	ROUTINE	-	-
Serial cognitive assessment	Daily MoCA or appropriate testing	Improvement in score	-	ROUTINE	-	-
Monitoring for overdrainage	Headache, subdural hematoma, drain displacement	No complications	-	ROUTINE	-	-

Extended Drain Sensitivity: 80-90% sensitive for predicting shunt response (more sensitive than single tap test at 50-60%) Duration: Typically 3-5 days of continuous drainage with serial assessments

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3. TREATMENT

3A. Acute/Emergent

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
Acetazolamide	PO	Temporizing measure while awaiting surgery; reduces CSF production	250 mg :: PO :: BID :: Start 250 mg BID; titrate to 250 mg TID or 500 mg BID; max 2 g/day	Sulfa allergy; severe hepatic/renal disease; hypokalemia; metabolic acidosis	BMP for potassium, bicarbonate; paresthesias	-	ROUTINE	ROUTINE	-
Serial therapeutic LP	LP	Temporizing measure; confirm continued benefit; bridge to surgery	30-50 mL :: LP :: q1-4 weeks :: Remove 30-50 mL every 1-4 weeks based on symptom recurrence	Coagulopathy; anticoagulation; skin infection	Post-LP symptoms; duration of benefit	-	ROUTINE	ROUTINE	-

3B. Symptomatic Treatments

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
Memantine	PO	Cognitive symptoms; may provide modest benefit pending surgery	5 mg :: PO :: daily :: Start 5 mg daily; increase by 5 mg/week; target 10 mg BID	Severe renal impairment (adjust dose if CrCl <30)	Confusion, dizziness	-	ROUTINE	ROUTINE	-
Donepezil	PO	Cognitive symptoms if AD component suspected	5 mg :: PO :: qHS :: Start 5 mg qHS x 4-6 weeks; increase to 10 mg qHS	Sick sinus syndrome; GI bleeding; COPD	Bradycardia, GI symptoms	-	ROUTINE	ROUTINE	-
Oxybutynin	PO	Urinary urgency/incontinence	5 mg :: PO :: BID :: Start 5 mg BID; may increase to 5 mg TID; or use ER 10-30 mg daily	Uncontrolled narrow-angle glaucoma; urinary retention; GI obstruction	Anticholinergic effects; cognitive worsening	-	ROUTINE	ROUTINE	-
Mirabegron	PO	Urinary urgency if anticholinergics contraindicated or cause cognitive worsening	25 mg :: PO :: daily :: Start 25 mg daily; may increase to 50 mg daily	Severe uncontrolled hypertension	Blood pressure	-	ROUTINE	ROUTINE	-
Tamsulosin	PO	Urinary retention (males with BPH component)	0.4 mg :: PO :: daily :: Start 0.4 mg daily; may increase to 0.8 mg daily	Orthostatic hypotension; planned cataract surgery (IFIS)	Orthostatic hypotension	-	ROUTINE	ROUTINE	-
Trazodone	PO	Sleep disturbance; sundowning	25 mg :: PO :: qHS :: Start 25-50 mg qHS; titrate to 50-150 mg qHS	Concurrent MAOIs; QT prolongation	Orthostatic hypotension	-	ROUTINE	ROUTINE	-
Physical therapy	-	Gait training and fall prevention	Per PT evaluation :: - :: - :: Initial evaluation plus ongoing therapy for gait training, balance, strength	None	Fall risk assessment	-	ROUTINE	ROUTINE	-

3C. Definitive Treatment (Shunt Surgery)

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
Ventriculoperitoneal (VP) shunt	Surgical	Definitive treatment for NPH; positive tap test or extended drain trial	Programmable valve :: Surgical :: - :: Valve pressure setting adjusted based on symptoms; typical starting setting 120-180 mmH2O	Active peritoneal infection; peritoneal adhesions; recent abdominal surgery; ascites	Post-op neuro checks; shunt series imaging; valve setting verification	-	ROUTINE	ROUTINE	-
Ventriculoatrial (VA) shunt	Surgical	Alternative if peritoneum unsuitable (adhesions, peritonitis history)	Programmable valve :: Surgical :: - :: Catheter tip in right atrium; valve adjusted as VP shunt	Active bacteremia; severe cardiac disease; pulmonary hypertension	Post-op neuro checks; shunt series imaging; valve setting verification; cardiac monitoring; watch for shunt nephritis	-	EXT	-	-
Lumboperitoneal (LP) shunt	Surgical	Alternative approach; avoids cranial surgery	Programmable valve :: Surgical :: - :: Catheter from lumbar subarachnoid space to peritoneum	Spinal stenosis; arachnoiditis; Chiari malformation	Post-op neuro checks; shunt series imaging; valve setting verification; watch for overdrainage with positional changes	-	EXT	-	-
Endoscopic third ventriculostomy (ETV)	Surgical	Secondary NPH with aqueductal stenosis	N/A :: Surgical :: - :: Create opening between third ventricle and interpeduncular cistern	Communicating hydrocephalus (most iNPH); scarred prepontine cistern	Post-op neuro checks; repeat imaging	-	EXT	-	-

Shunt Valve Selection: - Programmable valves (Codman, Medtronic, Sophysa) preferred - allow non-invasive pressure adjustment - Anti-siphon devices reduce positional overdrainage - Gravitational valves help prevent overdrainage in upright position

3D. Post-Shunt Complication Management

Treatment	Route	Indication	Dosing	Contraindications	Monitoring	ED	HOSP	OPD	ICU
Valve pressure adjustment (overdrainage)	External	Overdrainage symptoms (headache, subdural hematoma)	Increase setting :: External programming :: - :: Increase opening pressure by 20-30 mmH2O increments; recheck in 1-2 weeks	None	Symptom response; repeat imaging	-	ROUTINE	ROUTINE	-
Valve pressure adjustment (underdrainage)	External	Underdrainage (persistent or worsening NPH symptoms)	Decrease setting :: External programming :: - :: Decrease opening pressure by 20-30 mmH2O increments; recheck in 1-2 weeks	None	Symptom response; repeat imaging	-	ROUTINE	ROUTINE	-
Vancomycin	IV	Shunt infection (empiric)	15-20 mg/kg :: IV :: q8-12h :: 15-20 mg/kg IV q8-12h; adjust for renal function; target trough 15-20 mcg/mL	Vancomycin allergy	Vancomycin trough; renal function	STAT	STAT	-	STAT
Cefepime	IV	Shunt infection (empiric gram-negative coverage)	2 g :: IV :: q8h :: 2 g IV q8h; adjust for renal function	Cephalosporin allergy	Renal function	STAT	STAT	-	STAT
Shunt revision surgery	Surgical	Shunt malfunction, obstruction, or infection	Per neurosurgery :: Surgical :: - :: Shunt externalization if infected; revision for mechanical failure	Active systemic infection	Post-op monitoring; infection clearance	-	URGENT	-	-

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4. OTHER RECOMMENDATIONS

4A. Referrals & Consults

Recommendation	ED	HOSP	OPD	ICU
Neurology for comprehensive evaluation, differential diagnosis, and coordination of diagnostic workup	-	ROUTINE	ROUTINE	-
Neurosurgery for shunt candidacy evaluation after positive tap test or extended drain trial	-	ROUTINE	ROUTINE	-
Neuropsychology for baseline cognitive assessment and differentiation from other dementias (AD, vascular)	-	-	ROUTINE	-
Physical therapy for gait assessment, fall prevention, and baseline measurement for tap test comparison	-	ROUTINE	ROUTINE	-
Occupational therapy for ADL assessment, home safety evaluation, and cognitive strategies	-	ROUTINE	ROUTINE	-
Urology for evaluation if urinary symptoms prominent or atypical for NPH	-	-	ROUTINE	-
Social work for caregiver support, community resources, and care planning	-	ROUTINE	ROUTINE	-
Geriatrics or geriatric psychiatry for complex older patients with multiple comorbidities	-	ROUTINE	ROUTINE	-

4B. Patient Instructions

Recommendation	ED	HOSP	OPD
Return immediately if sudden severe headache, new weakness, or altered consciousness develops (may indicate shunt malfunction or complication)	STAT	STAT	ROUTINE
Report fever, incision redness, or drainage after shunt surgery (may indicate shunt infection)	STAT	STAT	ROUTINE
Keep scheduled follow-up appointments for shunt valve pressure adjustments and monitoring	-	ROUTINE	ROUTINE
Use assistive devices (walker, cane) as recommended by physical therapy to prevent falls	-	ROUTINE	ROUTINE
Do not drive until cleared by physician due to cognitive impairment and fall risk	-	ROUTINE	ROUTINE
Avoid MRI without confirming shunt valve is MRI-conditional and checking valve setting afterward	-	ROUTINE	ROUTINE
Carry shunt information card with valve type and current pressure setting	-	ROUTINE	ROUTINE

4C. Lifestyle & Prevention

Recommendation	ED	HOSP	OPD
Fall precautions including removal of throw rugs, adequate lighting, grab bars in bathroom due to gait instability	-	ROUTINE	ROUTINE
Regular physical activity within safe limits to maintain strength and mobility	-	ROUTINE	ROUTINE
Cognitive stimulation through reading, puzzles, and social engagement to support cognitive reserve	-	-	ROUTINE
Blood pressure optimization (target <130/80) to reduce vascular contribution to cognitive impairment	-	ROUTINE	ROUTINE
Adequate hydration to maintain optimal CSF dynamics; avoid dehydration	-	ROUTINE	ROUTINE
Bladder training program in conjunction with physical therapy for urinary symptoms	-	ROUTINE	ROUTINE

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SECTION B: REFERENCE

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5. DIFFERENTIAL DIAGNOSIS

Alternative Diagnosis	Key Distinguishing Features	Tests to Differentiate
Alzheimer's disease	Memory impairment predominant; insidious progression; no significant gait disturbance early; no improvement with LP	MRI shows hippocampal atrophy >ventricular enlargement; CSF low Abeta-42, high tau; no tap test response
Vascular dementia	Stepwise decline; focal neurological signs; executive dysfunction; vascular risk factors	MRI shows extensive white matter disease, strategic infarcts; ventriculomegaly less prominent
Parkinson's disease	Rest tremor; rigidity; bradykinesia; shuffling gait differs from NPH magnetic gait; no incontinence early	DaTscan abnormal; no tap test response; no ventriculomegaly disproportionate to atrophy
Dementia with Lewy bodies	Visual hallucinations; fluctuating cognition; parkinsonism; REM sleep behavior disorder	DaTscan abnormal; no ventricular enlargement out of proportion to atrophy
Progressive supranuclear palsy	Vertical gaze palsy; postural instability with falls backward; axial rigidity	MRI midbrain atrophy ("hummingbird sign"); no tap test response
Cervical spondylotic myelopathy	Upper motor neuron signs in legs; hyperreflexia; Babinski; sensory level	Cervical MRI shows cord compression; EMG findings
Peripheral neuropathy	Sensory loss distally; reduced reflexes; no cognitive or urinary symptoms	EMG/NCS confirms peripheral nerve involvement
Obstructive hydrocephalus	Acute onset; headache; papilledema; elevated opening pressure on LP	MRI shows obstructive lesion; elevated ICP; requires emergent intervention
Spinal stenosis	Neurogenic claudication; leg pain with walking relieved by rest/leaning forward	Lumbar MRI shows stenosis; normal brain imaging
Frontotemporal dementia	Behavioral changes prominent; personality changes; language impairment	MRI frontal/temporal atrophy; FDG-PET frontal hypometabolism

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6. MONITORING PARAMETERS

Parameter	Frequency	Target/Threshold	Action if Abnormal	ED	HOSP	OPD	ICU
Gait assessment (timed 10m walk, Tinetti)	Pre-LP, post-LP, each follow-up	Document baseline; track improvement	Positive change supports diagnosis; no change may indicate poor shunt candidacy	-	ROUTINE	ROUTINE	-
MoCA or MMSE	Baseline, post-LP, every 6 months	Track cognitive trajectory	Improvement suggests NPH; decline suggests alternative diagnosis or shunt failure	-	ROUTINE	ROUTINE	-
Post-shunt imaging (CT or MRI)	1-2 days post-op, 3 months, then PRN	Confirm ventricular decompression; rule out subdural hematoma	Repeat imaging if symptoms change; adjust valve	-	ROUTINE	ROUTINE	-
Shunt valve setting verification	After any MRI; at each clinic visit	Confirm setting unchanged (some valves reset in MRI)	Reprogram if reset; ensure appropriate setting	-	ROUTINE	ROUTINE	-
Neurological exam	Each clinic visit	Stable or improved gait, cognition, continence	Decline triggers workup for shunt malfunction or alternative diagnosis	-	ROUTINE	ROUTINE	-
Subdural hematoma surveillance	Post-shunt, especially if headache	No subdural collection	Adjust valve pressure higher; surgical evacuation if large/symptomatic	STAT	ROUTINE	ROUTINE	-
Signs of shunt infection	Post-operatively and ongoing	No fever, erythema, wound drainage	Blood/CSF cultures; shunt tap; IV antibiotics; possible shunt removal	STAT	ROUTINE	ROUTINE	-
Urinary symptom diary	Baseline and follow-up	Frequency, urgency, incontinence episodes	Adjust bladder medications; confirm NPH response	-	ROUTINE	ROUTINE	-
ADL/IADL function	Every 6 months	Stable or improved function	Increase support services; OT reassessment	-	ROUTINE	ROUTINE	-

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7. DISPOSITION CRITERIA

Disposition	Criteria
Discharge home	Stable symptoms; workup complete; awaiting outpatient tap test; caregiver support available
Admit to floor	Extended lumbar drain trial; post-shunt observation; shunt complication evaluation
Admit to ICU	Acute shunt malfunction with altered mental status; symptomatic overdrainage with large subdural; shunt infection with sepsis
Outpatient follow-up	Neurology 2-4 weeks after tap test to review results; Neurosurgery evaluation if positive tap test; post-shunt follow-up at 1-3 months, 6 months, then annually
Urgent neurosurgery referral	Positive tap test; positive extended drain trial; progressive symptoms with classic imaging findings

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8. EVIDENCE & REFERENCES

Recommendation	Evidence Level	Source
Evans index >0.3 diagnostic for ventriculomegaly	Class II, Level B	Relkin et al. Neurosurgery 2005 (iNPH Guidelines)
Callosal angle <90 degrees supports iNPH diagnosis	Class III, Level C	Virhammar et al. J Neurosurg 2014
DESH (disproportionately enlarged subarachnoid-space hydrocephalus) pattern	Class II, Level B	Hashimoto et al. AJNR 2010
High-volume LP (tap test) predicts shunt response	Class II, Level B	Marmarou et al. J Neurosurg 2005
Extended lumbar drainage more sensitive than single tap test	Class II, Level B	Walchenbach et al. J Neurol Neurosurg Psychiatry 2002
VP shunt improves symptoms in selected iNPH patients	Class II, Level B	Hebb et al. Can J Neurol Sci 2001
Programmable valves reduce revision surgery rates	Class II, Level B	Zemack et al. Eur J Neurol 2003
Gait improvement most responsive to shunting	Class II, Level B	Mori et al. Neurol Med Chir 2012
Short symptom duration predicts better shunt outcome	Class II, Level B	Relkin et al. Neurosurgery 2005
CSF biomarkers help differentiate NPH from AD	Class III, Level C	Tarnaris et al. Neurology 2011
Shunt infection rate 5-10%; requires shunt removal for treatment	Class III, Level C	McGirt et al. J Neurosurg 2003
Japanese iNPH Guidelines diagnostic criteria	Class II, Level B	Mori et al. Neurol Med Chir 2012

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CHANGE LOG

v1.1 (January 30, 2026) - Standardized lab tables (1A, 1B, 1C) to Test (CPT) | ED | HOSP | OPD | ICU | Rationale | Target Finding format with CPT codes - Standardized imaging tables (2A, 2B, 2C) to Study (CPT) | ED | HOSP | OPD | ICU | Timing | Target Finding | Contraindications format with CPT codes - Standardized LP studies table with CPT codes and standard column order - Fixed structured dosing first fields to starting_dose :: route :: frequency :: full_instructions format - Expanded "Same as VP" cross-references in VA and LP shunt monitoring columns - Added VERSION/CREATED/REVISED header block - Added additional clinical synonyms - Renamed CLINICAL SYNONYMS to SYNONYMS for consistency

v1.0 (January 27, 2026) - Initial template creation - Comprehensive diagnostic workup including imaging criteria (Evans index, callosal angle, DESH) - High-volume LP (tap test) protocol with detailed assessment criteria - Extended lumbar drain trial protocol - Shunt surgery options (VP, VA, LP, ETV) with valve selection guidance - Post-shunt complication management - Structured dosing format for symptomatic treatments - Differentiation from other dementias (AD, vascular, DLB, PSP) - PubMed citations with verified PMIDs

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APPENDIX A: NPH IMAGING CRITERIA

Evans Index Calculation

• Evans index = Maximum width of frontal horns / Maximum internal diameter of skull
• Positive: >0.3 (30%)

Callosal Angle

• Measured on coronal MRI at level of posterior commissure
• NPH: <90 degrees (acute angle from dilated ventricles)
• Atrophy: >90 degrees (wider angle)

DESH Pattern (Disproportionately Enlarged Subarachnoid-Space Hydrocephalus)

• Ventriculomegaly (Evans index >0.3)
• Tight high-convexity sulci (effaced sulci at vertex)
• Widened Sylvian fissures
• Focally dilated sulci

Additional Imaging Features

• Periventricular edema: Transependymal CSF flow seen as T2/FLAIR hyperintensity around ventricles
• Rounding of frontal horn angles: Suggests pressure effect
• Corpus callosum thinning: From stretching

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APPENDIX B: PREDICTORS OF SHUNT RESPONSE

Positive Predictors (Better Shunt Outcome)

Factor	Evidence
Gait disturbance as predominant symptom	Strong predictor
Short duration of symptoms (<6 months)	Moderate predictor
Known etiology (secondary NPH: SAH, meningitis, trauma)	Strong predictor
Positive tap test (>20% improvement in gait)	Moderate predictor
Positive extended lumbar drain trial (>30% improvement)	Strong predictor
Hyperdynamic aqueductal CSF flow on MRI	Weak predictor
Presence of B-waves on ICP monitoring	Moderate predictor

Negative Predictors (Poorer Shunt Outcome)

Factor	Evidence
Dementia predominant (gait normal)	Strong negative predictor
Long symptom duration (>2 years)	Moderate negative predictor
Severe cognitive impairment at baseline	Moderate negative predictor
Significant cortical atrophy	Moderate negative predictor
Negative tap test	Weak negative predictor
Comorbid Alzheimer's disease pathology	Strong negative predictor

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APPENDIX C: SHUNT COMPLICATION OVERVIEW

Complication	Incidence	Presentation	Management
Overdrainage (subdural hematoma)	2-17%	Headache worse when upright; new neurological deficits	Increase valve pressure; bed rest; surgical evacuation if large/symptomatic
Overdrainage (slit ventricle syndrome)	5-10%	Positional headaches; small ventricles on imaging	Increase valve pressure; anti-siphon device
Underdrainage	10-15%	Persistent or worsening NPH symptoms	Decrease valve pressure; evaluate for obstruction
Shunt infection	5-10%	Fever; wound erythema; mental status change	IV antibiotics; shunt externalization/removal
Shunt obstruction	5-15%	Symptom recurrence; inability to pump reservoir	Shunt revision surgery
Seizures	3-5%	New-onset seizures post-operatively	Antiepileptic medication
Abdominal complications (VP)	5-10%	Abdominal pain; pseudocyst; bowel perforation	Imaging evaluation; possible revision