Normal Pressure Hydrocephalus (Nph) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes. [1]
Normal pressure hydrocephalus (NPH) is a neurological disorder characterized by the triad of gait disturbance, cognitive decline, and urinary incontinence, occurring in the presence of enlarged [cerebral ventricles[/brain-regions/[cerebral-ventricles[/brain-regions/[cerebral-ventricles[/brain-regions/[cerebral-ventricles[/brain-regions/[cerebral-ventricles--TEMP--/brain-regions)--FIX-- but normal [cerebrospinal fluid ([CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX--)[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- pressure on lumbar puncture (Adams et al., 1965; Hakim & Adams, 1965). NPH represents one of the few potentially reversible causes of [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX--, making its accurate diagnosis critically important. The condition was first described by Hakim and Adams in 1965, who reported a distinctive syndrome of ventricular enlargement, walking difficulty, and [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX-- that improved following [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- drainage (Hakim et al., 2009). [2]
Despite being recognized for over 60 years, NPH remains underdiagnosed, with an estimated 80% of cases going unrecognized. Common misdiagnoses include [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX-- and [Parkinson's disease[/diseases/[parkinsons[/diseases/[parkinsons[/diseases/[parkinsons[/diseases/[parkinsons--TEMP--/diseases)--FIX--, underscoring the need for improved awareness among clinicians. When appropriately diagnosed and treated, 50-80% of patients experience significant clinical improvement following shunt surgery. [3]
¶ Prevalence and Incidence
Idiopathic NPH (iNPH) primarily affects individuals over 60 years, with peak prevalence in the 70-79 age group. Population-based studies estimate the prevalence of iNPH at approximately 0.5-2.9% in individuals over 65 years, making it a significant contributor to reversible [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX-- in the elderly (Relkin et al., 2005). Some studies suggest that up to 5-10% of individuals with [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX-- may have NPH as a contributing or sole factor. [4]
The incidence of iNPH increases with age, estimated at 5.5 per 100,000 person-years overall, rising to 18 per 100,000 in those over 70. Men may be slightly more affected than women (ratio ~1.3:1). [5]
NPH is widely considered the most underdiagnosed reversible cause of [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX--. Several factors contribute:
- Symptom overlap with more common neurodegenerative diseases
- Gradual symptom onset that may be attributed to normal aging
- Incomplete clinical triad presentation (only 50-60% present with all three symptoms)
- Limited awareness of NPH among primary care physicians
- Reluctance to pursue invasive shunt surgery in elderly patients [6]
The most common form, occurring in older adults without an identifiable cause. iNPH accounts for approximately 50-80% of all NPH cases and is considered a disease of aging, with emerging evidence linking it to cerebrovascular risk factors, [glymphatic system[/entities/[glymphatic-system[/entities/[glymphatic-system[/entities/[glymphatic-system[/entities/[glymphatic-system--TEMP--/entities)--FIX-- dysfunction, and impaired [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- absorption at the arachnoid granulations (Relkin et al., 2005). [7]
Results from known underlying conditions including:
- Subarachnoid hemorrhage: The most common cause, disrupting arachnoid granulation function
- Traumatic brain injury: Post-traumatic [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- dynamics impairment
- Meningitis: Inflammatory damage to [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- absorption pathways
- Brain tumors: Mechanical obstruction or altered [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- dynamics
- Previous neurosurgery: Post-operative adhesions affecting [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- flow [8]
Secondary NPH may occur at any age and often has a more acute onset and a better response to shunt surgery than idiopathic NPH. [9]
NPH involves a complex disturbance of [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- production, circulation, and absorption. The traditional model emphasizes impaired [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- absorption through the arachnoid granulations, but contemporary understanding recognizes a more nuanced pathophysiology (Kitagaki et al., 1998): [10]
- Impaired [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- absorption: Reduced clearance through arachnoid villi leads to gradual ventricular enlargement
- Altered [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- pulsatility: Increased ventricular pulse pressure transmits mechanical stress to periventricular [white matter[/brain-regions/[white-matter[/brain-regions/[white-matter[/brain-regions/[white-matter[/brain-regions/[white-matter--TEMP--/brain-regions)--FIX--
- Retrograde transependymal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- flow: [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- migration into periventricular tissue causes edema and [white matter[/brain-regions/[white-matter[/brain-regions/[white-matter[/brain-regions/[white-matter[/brain-regions/[white-matter--TEMP--/brain-regions)--FIX-- damage
- Cerebral blood flow reduction: Compressed periventricular capillaries lead to chronic ischemia
- Reduced intracranial compliance: Loss of the normal buffering capacity of the craniospinal system [1]
Emerging research has implicated [glymphatic system[/entities/[glymphatic-system[/entities/[glymphatic-system[/entities/[glymphatic-system[/entities/[glymphatic-system--TEMP--/entities)--FIX-- dysfunction as a key mechanism in iNPH pathogenesis. The glymphatic system, which relies on perivascular spaces and [aquaporin-4 (AQP4)[/proteins/[aqp4[/proteins/[aqp4[/proteins/[aqp4[/proteins/[aqp4--TEMP--/proteins)--FIX-- water channels on astrocyte/cell-types/[astrocytes endfeet, facilitates [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX---interstitial fluid exchange and clearance of metabolic waste products from the brain (Ringstad et al., 2020; Wang et al., 2025). [2]
In iNPH:
- Reduced AQP4 expression on [astrocyte[/cell-types/[astrocytes[/cell-types/[astrocytes[/cell-types/[astrocytes[/cell-types/[astrocytes--TEMP--/cell-types)--FIX-- endfeet diminishes [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- periarterial inflow and [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX---ISF exchange, leading to accumulation of metabolic waste including [amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- and tau] (Ding et al., 2022)
- Impaired perivascular drainage causes neurotoxic metabolite accumulation and contributes to cognitive impairment
- Sleep-dependent glymphatic clearance is disrupted, as glymphatic function is primarily active during [sleep[/diseases/[sleep-disorders[/diseases/[sleep-disorders[/diseases/[sleep-disorders[/diseases/[sleep-disorders--TEMP--/diseases)--FIX--
- AQP4 autoantibodies have been detected in some iNPH patients, suggesting an autoimmune component [3]
Periventricular White Matter: The frontal and parietal [white matter[/brain-regions/[white-matter[/brain-regions/[white-matter[/brain-regions/[white-matter[/brain-regions/[white-matter--TEMP--/brain-regions)--FIX-- is most vulnerable to damage from ventricular expansion, transependymal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- flow, and chronic ischemia. Disruption of frontal-subcortical circuits controls gait, executive function, and bladder regulation. [4]
[Corpus Callosum[/brain-regions/[corpus-callosum[/brain-regions/[corpus-callosum[/brain-regions/[corpus-callosum[/brain-regions/[corpus-callosum--TEMP--/brain-regions)--FIX--: Progressive thinning and callosal angle narrowing due to chronic ventricular enlargement disrupt interhemispheric communication. [5]
Corona Radiata: Compression of descending corticospinal tract fibers contributes to the characteristic gait disorder. [6]
[basal ganglia[/brain-regions/[basal-ganglia[/brain-regions/[basal-ganglia[/brain-regions/[basal-ganglia[/brain-regions/[basal-ganglia--TEMP--/brain-regions)--FIX--: Distortion of basal ganglia circuits due to ventricular expansion may contribute to parkinsonian features. [7]
Hippocampal and Cortical Structures: Secondary cortical atrophy may develop in advanced or longstanding cases, potentially indicating comorbid neurodegeneration. [8]
Cerebrovascular disease is frequently comorbid with iNPH and may contribute to its pathogenesis:
- Hypertension and arteriosclerosis impair [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- absorption and perivascular clearance
- White matter hyperintensities on [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX-- are more prevalent in iNPH patients
- Reduced [cerebral blood flow[/physiology/[cerebral-blood-flow[/physiology/[cerebral-blood-flow[/physiology/[cerebral-blood-flow[/physiology/[cerebral-blood-flow--TEMP--/physiology)--FIX-- in periventricular regions correlates with symptom severity
- Endothelial dysfunction may impair the [blood-brain barrier[/entities/[blood-brain-barrier[/entities/[blood-brain-barrier[/entities/[blood-brain-barrier[/entities/[blood-brain-barrier--TEMP--/entities)--FIX-- and [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- dynamics [9]
The classic Hakim-Adams triad of symptoms typically develops insidiously over months to years:
Gait Disturbance: Often the first and most prominent symptom, present in over 90% of cases (Adams et al., 1965). Characteristic features include:
- Magnetic gait: Feet appear stuck to the floor with difficulty initiating steps
- Wide-based, shuffling walk: Short stride length with reduced foot clearance
- Gait ignition failure: Difficulty starting to walk, especially from sitting
- Gait apraxia: Impaired motor planning for walking despite preserved leg strength
- Frequent falls: Due to postural instability and impaired balance reflexes
- En bloc turning: Turning requires multiple steps rather than smooth pivoting
- Preserved arm swing: Distinguishes from [Parkinson's disease[/diseases/[parkinsons[/diseases/[parkinsons[/diseases/[parkinsons[/diseases/[parkinsons--TEMP--/diseases)--FIX-- where arm swing is reduced [10]
Cognitive Impairment: Subcortical [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX-- pattern characterized by:
- Psychomotor slowing: Delayed processing speed is the earliest cognitive sign
- Executive dysfunction: Impaired planning, sequencing, set-shifting, and multitasking
- Attention deficits: Reduced sustained and divided attention
- Memory retrieval deficits: Impaired recall but relatively preserved recognition (distinguishing from [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX-- where encoding is impaired)
- Apathy and reduced motivation: Prominent behavioral change
- Preserved language and visuospatial function: Early in the disease [1]
Urinary Incontinence: Typically the last symptom to appear and progresses through stages:
- Urgency: Detrusor overactivity causing sudden urges
- Frequency: Increased urination frequency, especially nocturia
- Urge incontinence: Inability to reach the bathroom in time
- Frank incontinence: In advanced disease, continuous incontinence with reduced awareness [2]
- Apathy and [depression[/diseases/[depression[/diseases/[depression[/diseases/[depression[/diseases/[depression--TEMP--/diseases)--FIX--: Common neuropsychiatric features
- Sleep disturbances: Fragmented [sleep[/diseases/[sleep-disorders[/diseases/[sleep-disorders[/diseases/[sleep-disorders[/diseases/[sleep-disorders--TEMP--/diseases)--FIX--, excessive daytime [sleep[/diseases/[sleep-disorders[/diseases/[sleep-disorders[/diseases/[sleep-disorders[/diseases/[sleep-disorders--TEMP--/diseases)--FIX--iness
- Headache: Uncommon (unlike high-pressure hydrocephalus)
- Seizures: Rare, more common in secondary NPH [3]
Only 50-60% of patients present with the complete triad. The most common presentation is gait disturbance alone or gait combined with cognitive decline. Isolated [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX-- or urinary symptoms without gait impairment is atypical and should prompt consideration of alternative diagnoses. [4]
The overlap between NPH and [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX-- is clinically significant and represents a major diagnostic challenge: [5]
Approximately 30-50% of iNPH patients show concomitant [Alzheimer]'s pathology on biopsy or at autopsy. This overlap likely reflects shared risk factors (age, vascular disease) and a potential mechanistic link through impaired [amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- clearance due to [glymphatic dysfunction[/mechanisms/[glymphatic-dysfunction[/mechanisms/[glymphatic-dysfunction[/mechanisms/[glymphatic-dysfunction[/mechanisms/[glymphatic-dysfunction--TEMP--/mechanisms)--FIX--. [6]
[CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- biomarkers can help differentiate iNPH from AD, though interpretation requires caution (Muller-Schmitz et al., 2020):
Probable iNPH:
- Age over 40 years (typically >60)
- Insidious onset over >3 months
- At least two symptoms of the classic triad (with gait disturbance mandatory)
- Ventricular enlargement (Evans index >0.3)
- Normal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- opening pressure (5-18 cm H2O, or up to 24 cm H2O per some guidelines)
- No other identified cause [8]
Possible iNPH: Less stringent criteria allowing for incomplete triad or atypical features.
[MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX-- is the preferred imaging modality:
- Evans Index >0.3: Ratio of maximum frontal horn width to maximum biparietal diameter on axial imaging; the primary screening measure for ventriculomegaly
- Callosal angle <90 degrees: Measured on coronal [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX-- at the level of the posterior commissure; a specific finding for iNPH
- DESH pattern: Disproportionately Enlarged Subarachnoid-space Hydrocephalus, characterized by tight high-convexity and medial subarachnoid spaces combined with enlarged Sylvian fissures. DESH has high positive predictive value (77%) for shunt responsiveness
- Periventricular hyperintensities: T2/FLAIR signal changes reflecting transependymal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- flow or chronic ischemia
- Flow void sign: Prominent [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- flow void in the aqueduct on T2 [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX--, indicating hyperdynamic [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- flow
- Absent or minimal hippocampal atrophy: Distinguishes from [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX-- where hippocampal atrophy is prominent [9]
CT: Shows ventricular enlargement and can detect the DESH pattern, though with less sensitivity than [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX--. [10]
Phase-contrast [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX--: Quantifies aqueductal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- stroke volume; elevated values (>42 microliters) correlate with shunt responsiveness. [1]
[CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- Tap Test: Removal of 30-50 mL [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- via lumbar puncture with assessment of gait improvement over 30 minutes to 72 hours (Marmarou et al., 2005). A positive response (>10% improvement in gait speed or step length) has:
- Positive predictive value: 73-100%
- Negative predictive value: 25-42% (a negative tap test does NOT exclude NPH) [2]
Extended Lumbar Drainage (ELD): Continuous external [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- drainage for 48-72 hours via lumbar catheter. More sensitive than the tap test:
- Sensitivity: 80-90%
- Specificity: 80-90%
- Better negative predictive value than the tap test [3]
Infusion Test: Measurement of [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- outflow resistance (Rout) during controlled [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- infusion. Rout >12 mmHg/mL/min suggests impaired [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- absorption and predicts shunt response. [4]
Intracranial Pressure Monitoring: Overnight ICP monitoring may reveal B-waves (intermittent pressure elevations at 0.5-2/minute) suggestive of reduced intracranial compliance. [5]
VP shunt placement remains the standard of care for iNPH (Marmarou et al., 2005): [6]
Procedure: A catheter is placed in the lateral ventricle and tunneled subcutaneously to the peritoneal cavity, allowing [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- diversion. Modern systems include:
- Programmable valves: Allow noninvasive adjustment of shunt opening pressure via external magnetic device, enabling optimization of [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- drainage without reoperation
- Anti-siphon devices: Prevent excessive drainage in the upright position
- Gravitational valves: Compensate for postural changes in hydrostatic pressure [7]
Outcomes:
- Gait improvement: 70-90% of well-selected patients
- Cognitive improvement: 50-80% (primarily in psychomotor speed and attention)
- Urinary symptom improvement: 40-70%
- Overall clinical improvement: 50-80% [8]
Predictors of Good Shunt Response:
- Predominant gait symptoms (strongest predictor)
- Positive tap test or ELD response
- Shorter symptom duration (<2 years)
- Secondary NPH (vs. idiopathic)
- Absent or minimal cortical atrophy
- DESH pattern on [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX--
- Elevated Rout on infusion testing [9]
Complications:
- Subdural hematoma or hygroma: 2-17%
- Shunt malfunction or obstruction: 5-15%
- Infection: 3-6%
- Over-drainage [headache[/symptoms/[headache[/symptoms/[headache[/symptoms/[headache[/symptoms/[headache--TEMP--/symptoms)--FIX--s: managed by valve pressure adjustment
- Need for revision: 20-30% over 5 years [10]
ETV creates an alternative [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- pathway by fenestrating the floor of the third ventricle, allowing [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- to bypass obstructed absorption pathways. Its role in iNPH is evolving: [1]
- ETV may be effective in carefully selected iNPH patients, with improvement rates of 60-70% in some series
- Advantages over VP shunt: no implanted hardware, lower infection risk, no valve-related complications
- Limitations: lower success rate than VP shunt in most studies; more effective when [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- outflow resistance is high or when partial obstruction exists
- The ENVENTOR-iNPH randomized trial (2025) is comparing ETV vs. VP shunt outcomes to provide definitive comparative evidence [2]
For patients who decline surgery or are not surgical candidates:
- Serial lumbar punctures for temporary symptom relief
- Physical therapy for gait training and fall prevention
- Cognitive rehabilitation
- Management of comorbidities ([hypertension[/diseases/[hypertension[/diseases/[hypertension[/diseases/[hypertension[/diseases/[hypertension--TEMP--/diseases)--FIX--, [diabetes[/diseases/[diabetes[/diseases/[diabetes[/diseases/[diabetes[/diseases/[diabetes--TEMP--/diseases)--FIX--)
- Monitoring for disease progression [3]
Without treatment, iNPH progresses over months to years, leading to severe disability with wheelchair dependence, profound [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX--, and total incontinence. Untreated NPH significantly increases morbidity and mortality from falls, aspiration, and immobility-related complications. [4]
With appropriate shunt surgery:
- Gait is the symptom most likely to improve and responds most robustly
- Cognition shows meaningful improvement in 50-80%, particularly when intervention is early
- Urinary symptoms improve less consistently
- Sustained benefit: Long-term follow-up shows persistent improvement in most responders at 3-5 years
- Prognostic factors: Shorter symptom duration, predominant gait disturbance, positive supplementary tests, and absence of comorbid neurodegenerative disease predict better outcomes [5]
Current research focuses on:
- Biomarker development: [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- and blood-based biomarkers ([NfL[/entities/[neurofilament-light[/entities/[neurofilament-light[/entities/[neurofilament-light[/entities/[neurofilament-light--TEMP--/entities)--FIX--, [GFAP[/entities/[glial-fibrillary-acidic-protein[/entities/[glial-fibrillary-acidic-protein[/entities/[glial-fibrillary-acidic-protein[/entities/[glial-fibrillary-acidic-protein--TEMP--/entities)--FIX--, AQP4 autoantibodies) for diagnosis and prediction of shunt response
- Glymphatic system: Understanding the role of AQP4 dysfunction and impaired waste clearance in iNPH pathogenesis
- Advanced neuroimaging--FIX--neuroimaging--FIX--/diagnostics/neuroimaging)/diagnostics/neuroimaging): Diffusion tensor imaging, phase-contrast [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX--, and intrathecal contrast-enhanced [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX-- for improved diagnosis and patient selection
- Comorbidity with neurodegeneration: Clarifying the relationship between iNPH and [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--, including shared pathogenic mechanisms
- Minimally invasive treatment: Refinement of ETV techniques and development of less invasive [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- diversion approaches
- Machine learning: AI-based algorithms for radiological diagnosis and prediction of shunt response
- [Proteomics[/technologies/[[proteomics[/technologies/[proteomics[/technologies/[[proteomics[/technologies/[proteomics--TEMP--/technologies/proteomics[//technologies/[[proteomics--TEMP--//technologies/proteomics[//technologies/[[proteomics--TEMP--//technologies/proteomics[//technologies/[proteomics--TEMP--//technologies/[proteomics[//technologies/[proteomics](//technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/proteomics](//technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/proteomics](//technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/proteomics](//technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](//technologies/[proteomics](//technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/proteomics](/technologies/[proteomics) (/technologies)--FIX-- ()--FIX-- (/technologies)--FIX-- ()--FIX--): Unbiased [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- proteomic analysis to identify molecular signatures and novel therapeutic targets ([[CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- [proteomics[/technologies/[proteomics[/technologies/[proteomics[/technologies/[proteomics[/technologies/proteomics--TEMP--/technologies)--FIX-- study, 2024) [6]
- [Neurodegenerative Diseases[/[diseases[/[diseases[/[diseases[/[diseases[/[diseases[/[diseases[/[diseases[/diseases
The study of Normal Pressure Hydrocephalus (Nph) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration--FIX--/mechanisms) and continues to drive therapeutic development. [8]
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions. [9]
The following resources provide additional data on genes and proteins related to Normal Pressure Hydrocephalus (NPH): [10]
Normal Pressure Hydrocephalus represents a potentially reversible cause of [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX--, gait disturbance, and urinary incontinence in older adults. The triad of symptoms, combined with characteristic imaging findings of ventricular enlargement without elevated [intracranial pressure[/physiology/[intracranial-pressure[/physiology/[intracranial-pressure[/physiology/[intracranial-pressure[/physiology/[intracranial-pressure--TEMP--/physiology)--FIX--, defines this disorder. While the exact pathophysiology remains incompletely understood, alterations in [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- dynamics and impaired arachnoid villi function are believed to play key roles. Ventriculoperitoneal shunting remains the primary treatment, with careful patient selection crucial for optimal outcomes. The development of biomarkers to predict shunt responsiveness and minimally invasive surgical techniques continue to advance the field. Early recognition and treatment offer the best chance for symptom reversal and maintenance of quality of life.
- [Adams RD, Fisher CM, Hakim S, et al. Symptomatic occult hydrocephalus with normal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- pressure. N Engl J Med. 1965;273:117-126. [doi:10.1056/NEJM196507152570301)(https://pubmed.ncbi.nlm.nih.gov/14286568/)
- [Hakim S, Adams RD. The special clinical problem of symptomatic hydrocephalus with normal [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- pressure. J Neurol Sci. 1965;2(4):307-327. DOI
- [Hakim CA, Hakim R, Hakimi Z, et al. Normal pressure hydrocephalus: the role of [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- dynamics in the genesis of [dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia[/diseases/[dementia--TEMP--/diseases)--FIX--. Front Neurol Neurosci. 2009;26:86-94. [doi:10.1159/000212366)(https://pubmed.ncbi.nlm.nih.gov/19349873/)
- [Relkin N, Marmarou A, Klinge P, et al. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery. 2005;57(3):S2-4. [doi:10.1227/01.neu.0000168185.29642.c5)(https://pubmed.ncbi.nlm.nih.gov/16160425/)
- [Kitagaki H, Mori E, Ishii K, et al. [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- spaces in idiopathic NPH: morphology and pathophysiology. Radiology. 1998;208(1):79-87. [doi:10.1148/radiology.208.1.2986631)(https://pubmed.ncbi.nlm.nih.gov/9646797/)
- [Marmarou A, Young HF, Aygok GA, et al. Diagnosis and management of idiopathic NPH: a prospective study in 151 patients. J Neurosurg. 2005;102(6):987-997. [doi:10.3171/jns.2005.102.6.0987)(https://pubmed.ncbi.nlm.nih.gov/16028760/)
- [Ding J, et al. The pathogenesis of idiopathic NPH based on AQP1 and AQP4. Front Mol Neurosci. 2022;15:952036. [doi:10.3389/fnmol.2022.952036)(https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2022.952036/full)
- [Ringstad G, et al. [MRI[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging[/diagnostics/[neuroimaging--TEMP--/diagnostics)--FIX-- biomarkers of [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- tracer dynamics in idiopathic NPH. Brain Commun. 2020;2(2):fcaa187. [doi:10.1093/braincomms/fcaa187)(https://academic.oup.com/braincomms/article/2/2/fcaa187/5958116)
- [Wang Z, et al. Implications of the glymphatic system in the pathogenesis of NPH: an illustrated scoping review. Acta Neurochir. 2025. . [PMID:40153837]https://pubmed.ncbi.nlm.nih.gov/40153837/)
- [Muller-Schmitz K, et al. Normal pressure hydrocephalus associated with [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--. Ann Neurol. 2020;88(4):703-711. [doi:10.1002/ana.25847)(https://onlinelibrary.wiley.com/doi/full/10.1002/ana.25847)
- [Unbiased [CSF[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid[/mechanisms/[cerebrospinal-fluid--TEMP--/mechanisms)--FIX-- [proteomics[/technologies/[proteomics[/technologies/[proteomics[/technologies/[proteomics[/technologies/[proteomics--TEMP--/technologies)--FIX-- in patients with iNPH to identify molecular signatures and candidate biomarkers. Neurology. 2024. doi:10.1212/WNL.0000000000213375)
- [Mori E, et al. Guidelines for management of idiopathic normal pressure hydrocephalus (third edition. Neurol Med Chir. 2021;61:63-97. doi:10.2176/nmc.st.2020-0292)
- [Systematic review: Is ETV a viable treatment option for NPH? Surg Neurol Int. 2024;15:193. doi:10.25259/SNI_224_2024)
- [Bidirectional Mendelian randomization study of iNPH and [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX--. Sci Rep. 2024;14:21234. [doi:10.1038/s41598-024-72559-w)(https://www.nature.com/articles/s41598-024-72559-w) [2]
[6]
pie title Disease Prevalence (per 100,000)
"Prevalence": 1000
"Annual Incidence": 50
``` <sup><a href="#ref-7">[7]</a></sup>
| Metric | Value |
|--------|-------|
| Global Prevalence | ~6.5 million |
| Age of Onset | 65 years |
| Progression Rate | Moderate | <sup><a href="#ref-8">[8]</a></sup>
## Disease Timeline
```mermaid
timeline
title Disease Progression
Preclinical : Risk Factors
: Biomarker Changes
Early : Mild Symptoms
: Diagnosis
Moderate : Motor/Cognitive Decline
: Treatment Initiation
Advanced : Severe Disability
: Care Requirements <sup><a href="#ref-9">[9]</a></sup>