Idiopathic Normal Pressure Hydrocephalus (iNPH) is a treatable cause of gait disturbance, cognitive decline, and urinary incontinence in older adults. Emerging evidence demonstrates that iNPH frequently coexists with neurodegenerative movement disorders, particularly Progressive Supranuclear Palsy (PSP), Parkinson Disease, and Multiple System Atrophy. This page synthesizes the current evidence regarding the clinical, imaging, and pathological overlap between PSP and iNPH, with implications for diagnosis and management.
The coexistence of iNPH with neurodegenerative disorders is more common than previously recognized:
The presence of both conditions presents diagnostic challenges:
Both PSP and iNPH involve dysfunction of periventricular and subcortical structures:
Commonly Affected Regions:
Shared vascular risk factors may contribute to comorbidity:
The glymphatic system plays a role in both conditions:
Patients with PSP-iNPH comorbidity may present with:
Gait Disturbance — The hallmark of iNPH (magnetic gait) may coexist with PSP's postural instability and falls. Gait may show a combination of shuffling (iNPH) and broad-based stance (PSP).
Cognitive Impairment — Cognitive impairment in PSP includes frontal executive dysfunction, while iNPH produces a subcortical dysexecutive syndrome. The combination may lead to more severe cognitive decline.
Urinary Symptoms — PSP can cause urinary frequency and urgency through autonomic dysfunction, while iNPH produces urinary incontinence. Differentiating the contributions of each condition can be challenging.
Ocular Motor Signs — Vertical supranuclear gaze palsy is pathognomonic for PSP and helps distinguish PSP from isolated iNPH.
Clinical features suggesting PSP-iNPH overlap include:
Imaging findings that suggest comorbid PSP-iNPH:
| Finding | PSP Component | iNPH Component |
|---|---|---|
| Ventricular enlargement | Moderate (from atrophy) | Severe (out of proportion) |
| Midbrain atrophy | Present (hummingbird sign) | Absent or mild |
| Periventricular hyperintensities | Variable | Prominent |
| Callosal angle | Normal | <90° (supine) |
| Disproportionate enlargement of Sylvian fissures | No | Yes |
Key features distinguishing PSP from iNPH:
Management of PSP-iNPH comorbidity requires a multimodal approach:
Ventriculoperitoneal Shunting
PSP-Specific Treatments
Monitoring for Disease Progression
The presence of comorbid PSP-iNPH affects prognosis:
Shimada et al. (2025) — "Idiopathic normal pressure hydrocephalus concomitant with progressive supranuclear palsy" (PMID: 39826491)[1:2]
Agerskov et al. (2024) — Pathological study of iNPH and comorbid neurodegeneration[2:1]
Mestre et al. (2023) — iNPH in Parkinsonian disorders[5]
Related pages in NeuroWiki:
#PSP #normal-pressure-hydrocephalus #comorbidity #neurodegeneration #iNPH #movement-disorders #clinical-overlap
Shimada T et al. Idiopathic normal pressure hydrocephalus concomitant with progressive supranuclear palsy (2025). 2025. ↩︎ ↩︎ ↩︎
Agerskov C et al. Neuropathology of iNPH and comorbid neurodegeneration (2024). 2024. ↩︎ ↩︎
Moretti JE et al. Vascular risk factors in PSP and iNPH (2024). 2024. ↩︎
Litvan I et al. Diagnostic criteria for PSP (2024). 2024. ↩︎
Mestre TA et al. iNPH in Parkinsonian disorders: a systematic review (2023). 2023. ↩︎