Home › Conditions › Normal Pressure Hydrocephalus

Normal Pressure Hydrocephalus

A potentially reversible cause of dementia characterized by enlarged brain ventricles, gait disturbance, cognitive decline, and urinary incontinence, treatable with shunt surgery.

Overview

Normal pressure hydrocephalus (NPH) is a neurological disorder caused by the buildup of cerebrospinal fluid (CSF) in the brain's ventricles, leading to their enlargement despite normal or only slightly elevated intracranial pressure. This condition primarily affects older adults, typically those over 60 years of age, and is one of the few potentially reversible causes of dementia. The term "normal pressure" can be misleading, as the pressure may fluctuate and can be elevated at times, particularly during sleep.

NPH is characterized by a classic triad of symptoms: gait disturbance, cognitive impairment, and urinary incontinence. However, not all patients present with all three symptoms, and the onset is typically gradual over months to years. The condition affects approximately 700,000 Americans, though it's believed to be significantly underdiagnosed. Many cases are mistakenly attributed to Alzheimer's disease, Parkinson's disease, or simply aging.

What makes NPH particularly important in the field of neurology is its potential for treatment. Unlike most other causes of dementia, NPH symptoms can often be improved or even reversed with appropriate surgical intervention, typically involving the placement of a ventriculoperitoneal shunt. Early recognition and treatment are crucial, as prolonged symptoms may become irreversible due to permanent brain damage. This reversibility makes accurate diagnosis essential, though distinguishing NPH from other neurodegenerative conditions remains challenging.

Symptoms

The symptoms of normal pressure hydrocephalus typically develop gradually over months to years, often beginning so subtly that they're initially attributed to normal aging. The classic triad of symptoms—gait disturbance, cognitive decline, and urinary incontinence—may not all be present initially, and their severity can vary considerably among patients. Understanding the progression and characteristics of these symptoms is crucial for early recognition and treatment.

Warning Signs

Seek immediate medical attention if symptoms rapidly worsen, especially if accompanied by severe headache, vomiting, vision changes, or decreased consciousness, as these may indicate acute hydrocephalus requiring emergency treatment.

Primary Symptoms

Problems with Movement
Headache
Depressive or Psychotic Symptoms
Palpitations

The Classic Triad

Symptom Characteristics Typical Onset
Gait Disturbance Magnetic gait, shuffling, wide-based, difficulty initiating steps Usually first symptom
Cognitive Impairment Memory loss, slowed thinking, apathy, difficulty with attention Months after gait changes
Urinary Incontinence Urgency, frequency, eventual loss of control Often last to appear

Gait and Movement Problems

The gait disturbance in NPH is often the first and most prominent symptom:

  • Magnetic gait: Feet appear stuck to the floor, difficulty lifting feet
  • Shuffling steps: Short, slow steps with reduced foot clearance
  • Wide-based stance: Increased distance between feet for stability
  • Start hesitation: Difficulty initiating walking, "freezing"
  • Turning difficulty: Multiple small steps needed to turn
  • Postural instability: Increased fall risk, backward leaning
  • Preserved arm swing: Unlike Parkinson's disease

Cognitive Symptoms

Cognitive decline in NPH has specific characteristics:

  • Psychomotor slowing: Delayed responses, slow information processing
  • Memory impairment: Difficulty with recall more than recognition
  • Executive dysfunction: Problems with planning, organization, multitasking
  • Apathy: Loss of initiative, reduced spontaneous activity
  • Attention deficits: Difficulty concentrating, easily distracted
  • Preserved language: Speech typically remains intact early on

Urinary Symptoms

Bladder dysfunction follows a typical progression:

  • Increased frequency: Need to urinate more often
  • Urgency: Sudden, compelling need to urinate
  • Nocturia: Multiple nighttime bathroom trips
  • Urge incontinence: Inability to reach bathroom in time
  • Complete incontinence: Loss of bladder control awareness

Associated Symptoms

Additional symptoms may include:

  • Headaches - Often worse in morning or with position changes
  • Dizziness or vertigo
  • Visual disturbances - Difficulty looking up
  • Depression and anxiety
  • Sleep disturbances
  • Behavioral changes - Irritability, personality changes
  • Seizures (rare)

Symptom Timeline

Symptoms typically evolve over 6 months to several years. Gait problems usually appear first, followed by cognitive changes, with urinary symptoms often developing last. However, this sequence can vary, and some patients may present with only one or two components of the triad.

Causes

Normal pressure hydrocephalus occurs when cerebrospinal fluid (CSF) accumulates in the brain's ventricles, causing them to enlarge and compress surrounding brain tissue. Despite the name, intracranial pressure readings may be normal or only slightly elevated, though pressure can fluctuate, particularly during sleep. The exact mechanisms leading to CSF accumulation and symptom development are not fully understood, making NPH a complex condition to study and treat.

CSF Circulation and Dysfunction

Understanding normal CSF dynamics helps explain NPH pathophysiology:

  • Normal production: CSF is produced by choroid plexus at ~500mL/day
  • Circulation path: Through ventricles to subarachnoid space
  • Absorption: Via arachnoid granulations into venous system
  • NPH mechanism: Imbalance between production and absorption
  • Ventricular enlargement: Gradual expansion compresses brain tissue

Types of NPH

Idiopathic NPH (iNPH)

The most common form with no identifiable cause:

  • Accounts for about 50% of cases
  • Typically affects adults over 60
  • May involve age-related changes in CSF dynamics
  • Possible genetic predisposition
  • Gradual onset over months to years

Secondary NPH

Results from known conditions affecting CSF circulation:

  • Head trauma: Even mild injuries can trigger NPH
  • Subarachnoid hemorrhage: Blood irritates absorption pathways
  • Meningitis: Inflammation damages CSF absorption sites
  • Brain tumors: Can obstruct CSF flow
  • Previous brain surgery: Scarring affects CSF dynamics
  • Intraventricular hemorrhage: Common in premature infants

Pathophysiological Mechanisms

CSF Absorption Impairment

  • Reduced function of arachnoid granulations
  • Increased resistance to CSF outflow
  • Fibrosis of subarachnoid space
  • Venous drainage abnormalities

Brain Compliance Changes

  • Decreased brain elasticity with aging
  • Altered viscoelastic properties
  • Reduced ability to accommodate CSF fluctuations
  • White matter changes from chronic compression

Vascular Factors

Emerging evidence suggests vascular involvement:

  • Cerebrovascular disease: Often coexists with NPH
  • Reduced cerebral blood flow: Particularly in periventricular regions
  • Arterial pulsations: May contribute to ventricular enlargement
  • Venous compliance: Changes affect CSF absorption
  • Blood-brain barrier: Dysfunction may play a role

Why Symptoms Occur

Anatomical Compression

  • Motor fibers: Compression causes gait disturbance
  • Frontal regions: Leads to cognitive and behavioral changes
  • Bladder control centers: Results in urinary symptoms
  • White matter tracts: Disruption affects multiple functions

Metabolic Changes

  • Reduced blood flow to affected areas
  • Impaired waste removal
  • Altered neurotransmitter function
  • Oxidative stress from chronic compression

Risk Factors

Understanding the risk factors for normal pressure hydrocephalus helps identify individuals who may be more susceptible to developing this condition. While NPH can occur without any identifiable risk factors (idiopathic NPH), certain conditions and characteristics increase the likelihood of developing the disorder. Recognition of these factors is important for early detection and appropriate screening.

Age-Related Factors

  • Advanced age: Most common in people over 60 years
  • Peak incidence: Between 70-80 years of age
  • Rare before 40: Should prompt search for secondary causes
  • Age-related brain changes: Decreased compliance, vascular changes

Medical Conditions

Neurological Conditions

  • Previous head trauma: Even mild injuries increase risk
  • History of meningitis: Bacterial or viral
  • Subarachnoid hemorrhage: From aneurysm or trauma
  • Brain tumors: Particularly those near ventricles
  • Previous neurosurgery: Can affect CSF dynamics
  • Aqueductal stenosis: Narrowing of CSF pathways

Vascular Risk Factors

  • Hypertension: Associated with small vessel disease
  • Diabetes: Vascular complications may contribute
  • Cardiovascular disease: Affects cerebral blood flow
  • Cerebrovascular disease: Often coexists with NPH
  • Atrial fibrillation: May affect venous drainage

Demographic Factors

  • Gender: Slightly more common in men
  • Race: No clear racial predisposition identified
  • Geographic location: No specific geographic clustering
  • Socioeconomic status: May affect diagnosis rates

Genetic Factors

While most NPH is sporadic, genetic factors may play a role:

  • Rare familial cases reported
  • Possible genetic susceptibility
  • APOE ε4 allele association unclear
  • Family history of dementia may increase risk

Environmental and Lifestyle Factors

  • Occupational head trauma: Contact sports, military service
  • Alcohol abuse: May affect brain compliance
  • Sedentary lifestyle: Possible indirect effect
  • Sleep disorders: May affect CSF dynamics

Conditions That May Mimic or Coexist

Risk Assessment

Having risk factors doesn't guarantee developing NPH. However, individuals with multiple risk factors, especially those over 60 with gait changes, cognitive decline, or urinary symptoms, should be evaluated for NPH, as early diagnosis and treatment can significantly improve outcomes.

Diagnosis

Diagnosing normal pressure hydrocephalus is challenging because its symptoms overlap with many other conditions affecting older adults, including Alzheimer's disease, Parkinson's disease, and vascular dementia. The diagnosis requires a combination of clinical assessment, neuroimaging, and often diagnostic CSF drainage tests. No single test can definitively diagnose NPH, making it crucial to use a systematic approach that considers all available evidence.

Clinical Assessment

Detailed History

  • Symptom onset: Gradual progression over months to years
  • Symptom order: Typically gait, then cognitive, then urinary
  • Medical history: Previous head trauma, infections, hemorrhage
  • Medication review: Rule out drug-induced symptoms
  • Family observations: Often provide crucial timeline information

Physical Examination

  • Gait assessment: Observe for magnetic gait, shuffling
  • Neurological exam: Usually normal reflexes, no focal deficits
  • Cognitive testing: Mini-Mental State Exam, Montreal Cognitive Assessment
  • Balance tests: Romberg test, pull test
  • Continence assessment: Bladder diary may be helpful

Neuroimaging

MRI Brain (Preferred)

Key findings suggestive of NPH:

  • Ventriculomegaly: Enlarged ventricles out of proportion to sulci
  • Evans index >0.3: Ratio of ventricular to skull width
  • Callosal angle <40°: On coronal images
  • Periventricular changes: White matter hyperintensities
  • Aqueductal flow void: Increased CSF flow
  • DESH pattern: Disproportionately enlarged subarachnoid space hydrocephalus

CT Scan

Alternative when MRI unavailable:

  • Shows ventricular enlargement
  • Less sensitive for subtle changes
  • Cannot assess CSF flow
  • Useful for ruling out other pathology

CSF Diagnostic Tests

Large Volume Lumbar Puncture (Tap Test)

  • Procedure: Remove 30-50 mL of CSF
  • Timing: Assess symptoms before and after (hours to days)
  • Positive response: Temporary improvement in gait or cognition
  • Sensitivity: 26-61%
  • Specificity: 33-100%
  • Opening pressure: Usually normal (70-245 mm H2O)

External Lumbar Drainage (ELD)

  • Procedure: Continuous CSF drainage for 3-5 days
  • Volume: 10 mL/hour or 150-200 mL/day
  • Hospital admission: Required for monitoring
  • Higher sensitivity: 50-100%
  • Better predictor: Of shunt response than tap test

CSF Infusion Test

  • Measures resistance to CSF outflow
  • Specialized centers only
  • Can help confirm diagnosis
  • Risk of headache, infection

Additional Testing

Neuropsychological Testing

  • Detailed cognitive assessment
  • Helps differentiate from other dementias
  • Baseline for monitoring treatment response
  • Focus on executive function, processing speed

Gait Analysis

  • Quantitative gait assessment
  • Video analysis
  • Timed walking tests
  • Dual-task assessment

Differential Diagnosis

Conditions to consider and exclude:

Diagnostic Criteria

Guidelines suggest probable NPH with:

  1. Ventriculomegaly on imaging
  2. At least 2 of the classic triad symptoms
  3. Symptoms not better explained by other conditions
  4. Normal or slightly elevated CSF pressure
  5. Improvement with CSF drainage (supportive)

Diagnostic Challenges

NPH can coexist with other neurodegenerative diseases, complicating diagnosis. Up to 75% of NPH patients may have Alzheimer's pathology. A positive response to CSF drainage doesn't guarantee long-term shunt success, but lack of response strongly predicts poor shunt outcome.

Treatment Options

The primary treatment for normal pressure hydrocephalus is surgical placement of a shunt system to divert excess cerebrospinal fluid. While this represents one of the few opportunities to potentially reverse dementia symptoms, patient selection is crucial as not everyone benefits from surgery. Treatment decisions must balance potential benefits against surgical risks, particularly in elderly patients with multiple comorbidities.

Surgical Treatment

Ventriculoperitoneal (VP) Shunt

The most common surgical treatment:

  • Procedure: Catheter placed from brain ventricle to peritoneal cavity
  • Shunt valve: Regulates CSF flow rate
  • Programmable valves: Allow non-invasive pressure adjustments
  • Surgery duration: Typically 60-90 minutes
  • Hospital stay: Usually 2-4 days
  • Success rate: 60-80% show improvement

Alternative Shunt Options

  • Ventriculoatrial (VA) shunt: Drains to right atrium of heart
  • Lumboperitoneal shunt: From lumbar spine to peritoneum
  • Ventriculopleural shunt: To pleural cavity (rare)
  • Choice depends on: Anatomy, previous surgeries, surgeon preference

Endoscopic Third Ventriculostomy (ETV)

  • Creates opening in third ventricle floor
  • No implanted hardware
  • Limited success in NPH
  • May be combined with shunt
  • Selected cases only

Patient Selection for Surgery

Good Surgical Candidates

  • Classic symptom triad present
  • Gait disturbance as primary symptom
  • Positive response to CSF drainage
  • Symptoms less than 2 years
  • Minimal comorbidities
  • Good functional status
  • Supportive imaging findings

Poor Surgical Candidates

  • Dementia as sole symptom
  • Severe cerebrovascular disease
  • Advanced Alzheimer's disease
  • Multiple medical comorbidities
  • Anticoagulation that cannot be stopped
  • Limited life expectancy

Post-Surgical Management

Immediate Post-operative Care

  • Monitor for complications
  • Gradual mobilization
  • Head CT to confirm placement
  • Antibiotics to prevent infection
  • Pain management

Shunt Adjustments

  • Programmable valves: Allow pressure changes without surgery
  • MRI precautions: May affect valve settings
  • Regular follow-up: Assess symptom response
  • Fine-tuning: May take several adjustments
  • Overdrainage signs: Headaches, subdural collections

Expected Outcomes

Symptom Improvement Timeline

  • Gait: Often improves within days to weeks
  • Urinary symptoms: May improve over weeks to months
  • Cognitive function: Variable, may take months
  • Best results: Within first 6 months
  • Continued improvement: Possible up to 1 year

Success Rates by Symptom

  • Gait improvement: 70-90%
  • Urinary improvement: 50-80%
  • Cognitive improvement: 50-70%
  • Overall improvement: 60-80%
  • Return to independent living: 40-60%

Non-Surgical Management

Conservative Measures

  • Physical therapy: Gait training, balance exercises
  • Occupational therapy: Daily living activities
  • Bladder management: Scheduled voiding, medications
  • Cognitive rehabilitation: Memory strategies
  • Fall prevention: Home safety modifications

Medications

Limited role but may help specific symptoms:

  • Acetazolamide: Reduces CSF production (limited evidence)
  • Diuretics: Theoretical benefit, not proven
  • Bladder medications: For urinary urgency
  • Depression treatment: If present
  • Avoid: Sedating medications that worsen cognition

Complications and Management

Shunt Complications

  • Infection (5-10%): Requires antibiotics, possibly shunt removal
  • Malfunction (25% at 1 year): Blockage or disconnection
  • Overdrainage: Headaches, subdural hematomas
  • Underdrainage: Persistent symptoms
  • Abdominal complications: Rare but may occur

Long-term Follow-up

  • Regular neurological assessments
  • Annual imaging if stable
  • Shunt series X-rays if symptoms recur
  • Neuropsychological testing
  • Quality of life assessments

Treatment Decision Making

The decision to proceed with shunt surgery should involve the patient, family, neurosurgeon, and neurologist. Consider the patient's overall health, symptom severity, potential for improvement, and surgical risks. A multidisciplinary approach ensures the best outcomes.

Prevention

While there is no guaranteed way to prevent normal pressure hydrocephalus, particularly the idiopathic form, certain measures may reduce the risk of developing secondary NPH or help maintain brain health as we age. Understanding preventable risk factors and implementing protective strategies may help reduce the likelihood of developing this condition.

Primary Prevention

Head Injury Prevention

  • Vehicle safety: Always wear seatbelts, use appropriate car seats
  • Fall prevention: Remove home hazards, improve lighting
  • Sports safety: Wear helmets for cycling, skiing, contact sports
  • Workplace safety: Use protective equipment in hazardous jobs
  • Balance exercises: Reduce fall risk in older adults

Infection Prevention

  • Vaccinations: Stay current with recommended vaccines
  • Meningitis prevention: Vaccination for high-risk groups
  • Prompt treatment: Early treatment of CNS infections
  • Good hygiene: Reduce infection risk

Cardiovascular Health

Maintaining vascular health may reduce NPH risk:

  • Blood pressure control: Manage hypertension
  • Diabetes management: Keep blood sugar controlled
  • Cholesterol management: Healthy levels reduce vascular disease
  • Regular exercise: Improves cerebral blood flow
  • Heart-healthy diet: Mediterranean diet may be beneficial
  • Smoking cessation: Improves vascular health

Brain Health Maintenance

Cognitive Stimulation

  • Lifelong learning and education
  • Social engagement and activities
  • Mental challenges and puzzles
  • Learning new skills or languages
  • Reading and intellectual pursuits

Physical Activity

  • Regular aerobic exercise
  • Strength training
  • Balance and coordination exercises
  • Yoga or tai chi for flexibility
  • Dancing for coordination and social interaction

Early Detection and Monitoring

High-Risk Individuals

Those with risk factors should monitor for early signs:

  • Regular check-ups after age 60
  • Report gait changes to healthcare providers
  • Document cognitive changes
  • Keep bladder diary if symptoms develop
  • Annual cognitive screening if at risk

Post-Injury Monitoring

After head trauma or CNS infections:

  • Long-term neurological follow-up
  • Watch for delayed symptom onset
  • Report new neurological symptoms
  • Consider baseline imaging if severe injury

Lifestyle Modifications

  • Sleep hygiene: Quality sleep supports brain health
  • Stress management: Chronic stress affects brain function
  • Limit alcohol: Excessive use may affect brain compliance
  • Stay hydrated: Supports CSF production and circulation
  • Manage medications: Review drugs that affect cognition

Secondary Prevention

For those diagnosed with NPH:

  • Shunt maintenance: Regular follow-ups
  • Infection prevention: Careful wound care
  • Fall prevention: Reduce injury risk
  • Medication compliance: As prescribed
  • Lifestyle optimization: Support overall health

Prevention Limitations

While these measures may help reduce risk, idiopathic NPH often occurs without identifiable risk factors. The best strategy is maintaining overall brain health and seeking prompt evaluation if symptoms develop, as early treatment offers the best outcomes.

When to See a Doctor

Recognizing when to seek medical attention for symptoms that might indicate normal pressure hydrocephalus is crucial, as early diagnosis and treatment can significantly improve outcomes. Many people dismiss early symptoms as normal aging, but the combination of specific symptoms should prompt medical evaluation.

Seek Immediate Emergency Care If:

  • Sudden severe headache with vomiting
  • Rapid deterioration in consciousness
  • New onset seizures
  • Sudden inability to walk
  • Signs of shunt malfunction (if already treated)
  • High fever with headache and confusion

Schedule Urgent Appointment For:

  • Progressive difficulty walking over weeks to months
  • Frequent falls without clear cause
  • New urinary incontinence in older adults
  • Rapid cognitive decline
  • Combination of gait, memory, and bladder problems
  • Personality changes with walking difficulty

Consult Your Doctor If You Notice:

Gait Changes

  • Shuffling or magnetic gait
  • Difficulty initiating walking
  • Feeling unsteady or off-balance
  • Need to hold onto furniture while walking
  • Taking smaller steps than before

Cognitive Changes

  • Increased forgetfulness beyond normal aging
  • Difficulty concentrating or paying attention
  • Problems with planning or organization
  • Apathy or loss of interest in activities
  • Slowed thinking or responses

Urinary Symptoms

  • Sudden urgency to urinate
  • Inability to reach bathroom in time
  • Increased frequency, especially at night
  • New onset incontinence

For Those Already Diagnosed

Contact Your Neurosurgeon If:

  • Return of symptoms after initial improvement
  • New headaches, especially positional
  • Signs of infection (fever, wound redness)
  • Abdominal pain or swelling
  • Confusion or altered mental status
  • Vision changes

What to Tell Your Doctor

  • Timeline: When each symptom started
  • Progression: How symptoms have changed
  • Impact: Effect on daily activities
  • Medical history: Previous head injuries, infections
  • Medications: Current prescriptions and supplements
  • Family observations: Changes others have noticed

Which Specialist to See

  • Primary care physician: Initial evaluation and referral
  • Neurologist: Specialized evaluation and diagnosis
  • Neurosurgeon: If surgical treatment considered
  • Geriatrician: For older adults with multiple conditions

Don't Delay Evaluation

NPH is often misdiagnosed as Alzheimer's disease, Parkinson's disease, or normal aging. If you notice the characteristic triad of symptoms—walking problems, memory issues, and bladder control problems—insist on evaluation for NPH, especially if symptoms developed over months rather than years.

Frequently Asked Questions

What exactly is "normal pressure" in NPH?

The term "normal pressure" is somewhat misleading. While a single lumbar puncture may show normal CSF pressure (70-245 mm H2O), continuous monitoring reveals that pressure can fluctuate and may be elevated, particularly during sleep. The key feature is that ventricles are enlarged despite pressure readings that aren't consistently high.

How successful is shunt surgery for NPH?

Success rates vary but generally 60-80% of carefully selected patients show improvement after shunt surgery. Gait problems tend to improve most (70-90%), followed by bladder control (50-80%) and cognitive function (50-70%). Best results occur when surgery is performed early in the disease course.

Can NPH be cured?

While NPH cannot be "cured" in the traditional sense, symptoms can often be significantly improved or even reversed with shunt surgery. However, the shunt must remain in place permanently, and some patients may experience symptom recurrence over time due to shunt problems or disease progression.

How is NPH different from Alzheimer's disease?

Key differences include: NPH typically presents with gait problems first (Alzheimer's with memory loss), NPH progresses over months (Alzheimer's over years), NPH causes magnetic gait (Alzheimer's has normal gait early on), and NPH may improve with treatment (Alzheimer's progressively worsens). However, the two can coexist.

What happens if NPH is left untreated?

Untreated NPH typically progresses slowly, leading to worsening gait problems with increased fall risk, progressive cognitive decline potentially to severe dementia, complete urinary incontinence, and eventual inability to walk or care for oneself. Early treatment prevents this progression.

Can you prevent NPH from developing?

There's no guaranteed prevention for idiopathic NPH. However, preventing head injuries, promptly treating CNS infections, managing cardiovascular risk factors, and maintaining overall brain health may reduce risk. For secondary NPH, preventing the causative conditions is key.

How long does it take to see improvement after shunt surgery?

Improvement timeline varies: gait often improves within days to weeks, bladder control may take weeks to months, and cognitive improvement is more variable, potentially taking several months. Most improvement occurs within the first 6 months, though continued gains are possible up to a year.

What are the signs that a shunt is failing?

Return of original NPH symptoms, new headaches (especially positional), nausea or vomiting, changes in mental status, vision problems, or abdominal pain at the shunt site. Any of these symptoms warrant immediate medical evaluation.

Can NPH develop in younger people?

While NPH typically affects people over 60, it can rarely occur in younger individuals, usually as secondary NPH following head trauma, hemorrhage, or infection. Idiopathic NPH in people under 40 is extremely rare and should prompt thorough investigation for underlying causes.

Medical Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

References

  1. Nakajima M, Yamada S, Miyajima M, et al. Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus. Neurol Med Chir (Tokyo). 2021;61(2):63-97.
  2. Giordan E, Palandri G, Lanzino G, et al. Outcomes and complications of different surgical treatments for idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis. J Neurosurg. 2019;131(4):1024-1036.
  3. Andersson J, Rosell M, Kockum K, et al. Prevalence of idiopathic normal pressure hydrocephalus: A prospective, population-based study. PLoS One. 2019;14(5):e0217705.
  4. Espay AJ, Da Prat GA, Dwivedi AK, et al. Deconstructing normal pressure hydrocephalus: Ventriculomegaly as early sign of neurodegeneration. Ann Neurol. 2017;82(4):503-513.
  5. Ringstad G, Vatnehol SAS, Eide PK. Glymphatic MRI in idiopathic normal pressure hydrocephalus. Brain. 2017;140(10):2691-2705.
  6. Toma AK, Papadopoulos MC, Stapleton S, et al. Systematic review of the outcome of shunt surgery in idiopathic normal-pressure hydrocephalus. Acta Neurochir (Wien). 2013;155(10):1977-1980.