Overview
Normal Pressure Hydrocephalus
1. Overview
Normal Pressure Hydrocephalus (NPH) is a potentially reversible cause of dementia characterized by ventricular enlargement with normal or intermittently elevated CSF pressure. It accounts for approximately 5% of all dementia cases and is uniquely treatable with CSF shunting.
The Hakim-Adams Triad
The classic clinical presentation includes three cardinal features:
-
Gait Disturbance (earliest and most responsive to treatment)
- Magnetic gait - feet appear "stuck to the floor"
- Broad-based, shuffling steps
- Reduced stride length and height
- Difficulty initiating walking
- Postural instability with frequent falls
-
Cognitive Impairment (subcortical pattern)
- Psychomotor slowing
- Executive dysfunction
- Memory impairment (less prominent than Alzheimer's)
- Apathy and inattention
-
Urinary Incontinence (latest to appear)
- Initially urinary urgency and frequency
- Progresses to frank incontinence
- May have fecal incontinence in advanced cases
Mnemonic: "Wet, Wacky, Wobbly"
- Wet = Urinary incontinence
- Wacky = Cognitive impairment
- Wobbly = Gait disturbance
Key Epidemiology
| Factor | Details |
|---|---|
| Age | Peak incidence >0 years |
| Prevalence | 1-2% of those >5 years |
| Gender | Males slightly more affected |
| Types | Idiopathic (iNPH) most common in elderly |
2. Pathophysiology
┌─────────────────────────────────────────────────────────────────────────────┐
│ NPH PATHOPHYSIOLOGY FLOWCHART │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ TRIGGERING FACTORS │ │
│ │ • Prior SAH, Meningitis, Head Trauma (Secondary NPH) │ │
│ │ • Age-Related Changes in CSF Dynamics (Idiopathic NPH) │ │
│ │ • Reduced CSF Absorption at Arachnoid Granulations │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ VENTRICULAR DILATION │ │
│ │ • CSF accumulation with pressure transmission │ │
│ │ • Stretching of periventricular white matter fibers │ │
│ │ • Corpus callosum and corona radiata affected │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ PERIVENTRICULAR WHITE MATTER DAMAGE │ │
│ │ • Descending motor fibers to legs (gait) │ │
│ │ • Frontal lobe connections (cognition) │ │
│ │ • Sacral motor fibers (bladder control) │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌──────────────────────┬──────────────────┬────────────────────┐ │
│ ↓ ↓ ↓ │ │
│ ┌─────────┐ ┌─────────────┐ ┌───────────────┐ │ │
│ │ GAIT │ │ COGNITIVE │ │ URINARY │ │ │
│ │APRAXIA │ │ IMPAIRMENT │ │ INCONTINENCE │ │ │
│ └─────────┘ └─────────────┘ └───────────────┘ │ │
│ │ │
└─────────────────────────────────────────────────────────────────────────────┘
Key Pathophysiological Concepts
- Normal Opening Pressure: Unlike obstructive hydrocephalus, CSF pressure is within normal range (10-18 cmH2O)
- Intermittent Pressure Waves: B-waves may occur during sleep causing transient elevation
- Ventricular Compliance: Progressive ventricular dilation compresses periventricular structures
- Leg Motor Fibers: Located close to ventricles, hence early gait involvement
Idiopathic vs Secondary NPH
| Feature | Idiopathic NPH | Secondary NPH |
|---|---|---|
| Cause | Unknown | Prior meningitis, SAH, trauma |
| Age | Elderly (>0) | Any age |
| Onset | Insidious | Months after insult |
| Shunt Response | 60-80% | Often better if early |
3. Clinical Features
History Taking
Essential Questions:
- When did gait problems begin? (usually first symptom)
- Has walking pattern changed? (shuffling, falls)
- Memory or concentration problems?
- Urinary urgency or accidents?
- Any prior meningitis, head injury, or brain surgery?
- Family history of dementia?
Gait Assessment
The gait disturbance in NPH is characteristic:
| Feature | Description |
|---|---|
| Magnetic gait | Feet appear glued to floor |
| Broad-based | Wide stance for stability |
| Short stride | Reduced step length |
| Shuffling | Minimal foot clearance |
| Turn difficulty | Multiple steps to turn |
| Postural instability | Impaired balance |
Timed Up-and-Go (TUG) Test:
- Patient rises from chair, walks 3 meters, turns, returns, sits
- Normal: <10 seconds
- NPH: Often >20 seconds
- Useful for monitoring treatment response
Cognitive Profile
- Subcortical pattern (unlike Alzheimer's cortical pattern)
- Psychomotor slowing predominates
- Executive dysfunction (planning, organization)
- Frontal release signs may be present
- Relatively preserved language and visuospatial skills
Physical Examination Findings
| System | Findings |
|---|---|
| Gait | Magnetic, broad-based, shuffling |
| Tone | Paratonic rigidity (gegenhalten) |
| Reflexes | May have brisk lower limb reflexes |
| Frontal signs | Grasp reflex, palmomental reflex |
| Cognition | Poor attention, slow processing |
4. Diagnosis
Diagnostic Criteria (International NPH Guidelines)
Probable iNPH:
- Insidious onset after age 40
- Duration >3-6 months
- Gait disturbance + at least one other triad feature
- Ventricular enlargement (Evans' index >0.3)
- No other condition explaining symptoms
- Positive CSF drainage test
Imaging Studies
MRI Brain (Gold Standard):
| Finding | Significance |
|---|---|
| Ventriculomegaly | Evans' index >.3 (frontal horn width/biparietal diameter) |
| DESH sign | Disproportionately Enlarged Subarachnoid-space Hydrocephalus |
| Callosal angle | <90° suggests NPH |
| Periventricular caps | T2/FLAIR hyperintensity around ventricles |
| Aqueductal flow void | Hyperdynamic CSF flow on MRI |
Evans' Index Calculation:
- Maximum width of frontal horns ÷ Maximum internal diameter of skull
- Normal: <0.3
- NPH: >0.3
CSF Dynamics Testing
Lumbar Puncture:
- Opening pressure typically normal (10-18 cmH2O)
- CSF analysis normal (rule out infection, hemorrhage)
Large Volume Lumbar Puncture (Tap Test):
- Remove 30-50 mL CSF
- Assess gait before and 1-4 hours after
- Improvement suggests shunt-responsive NPH
- Sensitivity ~50-60%, Specificity ~80%
Extended Lumbar Drainage (ELD):
- External lumbar drain for 3-5 days
- 10 mL/hour continuous drainage
- More sensitive than single tap test
- Sensitivity 80-90%
Infusion Test:
- Measures CSF outflow resistance (Rout)
- Rout >18 mmHg/mL/min suggests NPH
- Requires specialized equipment
5. Management Algorithm
┌─────────────────────────────────────────────────────────────────────────────┐
│ NPH MANAGEMENT ALGORITHM │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ SUSPECTED NPH (Hakim Triad + Ventricular Enlargement) │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ INITIAL WORKUP │ │
│ │ • MRI Brain: Confirm ventriculomegaly, Evans' index >0.3 │ │
│ │ • Exclude other causes: Alzheimer's, Parkinson's, vascular │ │
│ │ • Cognitive testing: MMSE, MoCA │ │
│ │ • Gait assessment: Timed Up-and-Go test │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ LARGE VOLUME TAP TEST │ │
│ │ • Remove 30-50 mL CSF via LP │ │
│ │ • Assess gait at 1 hour and 24 hours │ │
│ │ • Repeat TUG test │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌──────────────────────────────────────┐ │
│ │ IMPROVEMENT? │ │
│ └──────────────────────────────────────┘ │
│ ↓ YES ↓ NO │
│ ┌──────────────────────────┐ ┌──────────────────────────────────────┐ │
│ │ SHUNT RESPONSIVE │ │ EXTENDED LUMBAR DRAINAGE (ELD) │ │
│ │ High probability │ │ • 3-5 day continuous drainage │ │
│ │ Proceed to shunt │ │ • If improves → Shunt candidate │ │
│ │ surgery │ │ • If no improvement → Poor candidate │ │
│ └──────────────────────────┘ └──────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ VENTRICULOPERITONEAL SHUNT │ │
│ │ • Programmable valve preferred (adjustable pressure) │ │
│ │ • Gravitational/anti-siphon device reduces overdrainage │ │
│ │ • Post-op: Valve adjustments as needed │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ ↓ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ FOLLOW-UP & MONITORING │ │
│ │ • Gait, cognition assessment at 3, 6, 12 months │ │
│ │ • CT Head if new symptoms (subdural, shunt malfunction) │ │
│ │ • Valve pressure adjustments as needed │ │
│ │ • Watch for complications: Subdural hematoma, infection │ │
│ └─────────────────────────────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────────────────┘
Surgical Treatment: VP Shunt
Ventriculoperitoneal (VP) Shunt:
- Most common surgical intervention
- Diverts CSF from lateral ventricle to peritoneal cavity
- Programmable valves allow non-invasive pressure adjustments
Shunt Outcomes:
- 60-80% show improvement
- Gait improves most reliably
- Cognition and continence less predictable
- Best outcomes with early intervention
Shunt Complications
| Complication | Incidence | Management |
|---|---|---|
| Subdural hematoma/hygroma | 2-17% | Adjust valve to higher pressure |
| Infection | 5-10% | Antibiotics ± shunt revision |
| Shunt malfunction | 20-30% over 10 years | Shunt revision |
| Overdrainage | Variable | Programmable valve adjustment |
Alternative: ETV (Endoscopic Third Ventriculostomy)
- May be considered in some cases
- Creates internal CSF pathway
- Avoids shunt hardware and its complications
- Less commonly used for iNPH
6. Differentiating from Similar Conditions
NPH vs Other Dementias
| Feature | NPH | Alzheimer's | Vascular Dementia | Parkinson's |
|---|---|---|---|---|
| Gait | Early, magnetic | Late | Variable | Festinating |
| Memory | Moderate | Severe, early | Variable | Moderate |
| Imaging | Ventriculomegaly | Atrophy | White matter changes | Normal/mild atrophy |
| Tremor | Absent | Absent | Absent | Present |
| Tap test | Positive | Negative | Negative | Negative |
NPH vs Parkinson's Disease
Both have gait disturbance but key differences:
| Feature | NPH | Parkinson's |
|---|---|---|
| Gait | Magnetic, broad-based | Festinating, narrow-based |
| Tremor | No | Yes (rest tremor) |
| Rigidity | Paratonic | Cogwheel |
| Levodopa response | No | Yes |
| Imaging | Ventriculomegaly | Normal/mild atrophy |
7. Prognosis
Factors Predicting Good Shunt Response
| Factor | Favorable | Unfavorable |
|---|---|---|
| Duration | <6 months | > years |
| Gait predominant | Yes | No |
| Cause | Secondary (known) | Idiopathic |
| Tap test | Positive | Negative |
| Comorbidities | Few | Extensive vascular disease |
Outcomes After Shunting
| Symptom | Improvement Rate |
|---|---|
| Gait | 70-90% |
| Cognition | 50-70% |
| Continence | 40-60% |
Key Point: Earlier diagnosis and treatment leads to better outcomes. Delayed treatment allows irreversible white matter damage.
8. Complications
Disease Complications
- Progressive immobility and falls
- Aspiration pneumonia from dysphagia
- Pressure ulcers
- Urinary tract infections
- Caregiver burden
Shunt Complications
| Complication | Presentation | Management |
|---|---|---|
| Subdural collection | Headache, neurological decline | Valve adjustment, rarely drainage |
| Shunt infection | Fever, wound erythema | Antibiotics, shunt removal |
| Shunt obstruction | Symptom recurrence | Shunt revision surgery |
| Seizures | Post-operative | Anticonvulsants |
9. Special Considerations
Elderly Patients
- Higher surgical risk but still benefit from shunting
- Careful pre-operative optimization
- Consider frailty assessment
- Involve family in decision-making
Coexisting Conditions
Vascular Dementia:
- May coexist with NPH
- More extensive white matter changes on MRI
- Shunt response less predictable
Parkinson's Disease:
- May coexist with NPH
- Differentiation important as treatments differ
- Both may coexist requiring combined management
Anesthetic Considerations
- Often elderly with comorbidities
- Cognitive impairment affects consent process
- Post-operative delirium risk
- May need geriatric medicine input
10. Key Clinical Pearls
Exam-Focused Points
- Classic Triad Recognition: Wet, Wacky, Wobbly - but gait is usually first and most responsive
- Evans' Index: >0.3 on CT/MRI suggests ventricular enlargement
- Tap Test: 30-50 mL CSF removal with gait improvement suggests shunt response
- Magnetic Gait: Distinctive pattern - feet appear stuck to floor
- Distinguishing from Parkinson's: No tremor, no levodopa response, broad-based not narrow gait
- Treatment: VP shunt with programmable valve is definitive treatment
- Best Outcome Predictor: Short duration, gait predominant, positive tap test
Common Exam Scenarios
- Elderly patient with progressive gait difficulty, urinary incontinence, and memory problems
- MRI showing ventriculomegaly out of proportion to cortical atrophy
- Gait improvement after large volume LP
- Shunt complications (subdural collection, infection)
11. Patient Explanation
What is Normal Pressure Hydrocephalus?
"Your brain produces a fluid called cerebrospinal fluid (CSF) that normally flows around the brain and spinal cord and gets absorbed back into the bloodstream. In NPH, this fluid builds up in the ventricles - the hollow spaces inside the brain - causing them to enlarge and press on surrounding brain tissue.
This pressure causes three main problems:
- Walking difficulties - Your feet may feel 'stuck to the floor'
- Memory and thinking problems - Slowness in thinking and planning
- Bladder control problems - Urgency and sometimes incontinence
The good news is that NPH is one of the few treatable causes of these symptoms."
How is it Diagnosed?
"We diagnose NPH through:
- Brain scan (MRI) - Shows enlarged fluid spaces in the brain
- Lumbar puncture (tap test) - We remove some fluid and see if your walking improves
If you improve after the tap test, it's a good sign that permanently draining the fluid with a shunt will help."
What is the Treatment?
"The main treatment is a shunt - a thin tube placed under the skin that drains excess fluid from your brain to your abdomen where your body absorbs it naturally.
Modern shunts have adjustable valves that we can fine-tune without surgery using a special magnet if needed. About 70-80% of people see improvement, especially in walking."
12. Evidence & Guidelines
Key Guidelines
| Guideline | Organization | Year | Key Points |
|---|---|---|---|
| iNPH Guidelines | Japanese NPH Society | 2021 | Diagnostic criteria, tap test protocol |
| EAN-ESO Guidelines | European Academy of Neurology | 2023 | Imaging requirements, shunt indications |
| AAN Practice Parameter | American Academy of Neurology | 2005 | Diagnosis and management recommendations |
Landmark Studies
SINPHONI Trial (2010):
- Randomized trial of shunt surgery vs conservative management
- Demonstrated significant improvement in shunted patients
- Established basis for surgical intervention
SYGNAT Study (2023):
- Large multicenter study on shunt outcomes
- Confirmed long-term benefits of shunting
- Identified predictors of good response
Evidence-Based Recommendations
| Recommendation | Evidence Level |
|---|---|
| MRI for diagnosis | Strong |
| CSF tap test | Moderate |
| VP shunt for confirmed NPH | Moderate |
| Programmable valve use | Moderate |
| Extended lumbar drainage if tap test negative | Weak |
13. References
-
Williams MA, Relkin NR. Diagnosis and management of idiopathic normal-pressure hydrocephalus. Neurol Clin Pract. 2013;3(5):375-385.
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Mori E, et al. Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus: Second Edition. Neurol Med Chir (Tokyo). 2012;52(11):775-809.
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Hashimoto M, et al. Diagnosis of idiopathic normal pressure hydrocephalus is supported by MRI-based scheme: a prospective cohort study. Cerebrospinal Fluid Res. 2010;7:18.
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Relkin N, et al. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery. 2005;57(3 Suppl):S4-16.
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Kazui H, et al. Lumboperitoneal shunt surgery for idiopathic normal pressure hydrocephalus (SINPHONI-2): an open-label randomised trial. Lancet Neurol. 2015;14(6):585-594.
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European Association of Neurosurgery. Guidelines for the Diagnosis and Treatment of Idiopathic Normal Pressure Hydrocephalus. 2022.
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Israelsson H, et al. Vascular risk factors in INPH: A prospective case-control study. Neurology. 2017;88(6):577-585.