Normal pressure hydrocephalus
Reversible cause of dementia in older adults marked by the triad of magnetic gait, urinary incontinence, and cognitive decline with ventriculomegaly on imaging; diagnosed by high-volume lumbar puncture with gait testing and treated with ventriculoperitoneal shunting.
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What this article covers
- Overview
Definition: normal pressure hydrocephalus (NPH) is a syndrome of communicating hydrocephalus in older adults, characterized by the clinical triad of gait apraxia, urinary incontinence, and cognitive…
- Epidemiology
Age group: NPH is a disease of older adults, most commonly diagnosed after age 60, with incidence rising further with advancing age.
- Risk factors
Advancing age: the dominant risk factor; idiopathic NPH is essentially a disease of later life.
- Pathophysiology
CSF dynamics: NPH is classified as a communicating hydrocephalus, meaning CSF flows freely between the ventricles and subarachnoid space, but net CSF absorption is impaired at the arachnoid granulations relative to production.
- Clinical features
Classic triad, in order of typical appearance: gait disturbance first, then urinary incontinence, then cognitive impairment, though presentation and order can vary.
- Differential diagnosis
Alzheimer disease: presents with prominent early episodic memory loss rather than gait disturbance as the initial symptom, and imaging shows disproportionate hippocampal and cortical atrophy rather than isolated ventriculomegaly.
- Diagnosis
What establishes the diagnosis: the combination of the clinical triad, ventriculomegaly on imaging, and objective gait improvement after high-volume CSF removal establishes the diagnosis; no single test alone is sufficient.
- Management
First step once the diagnosis is supported by a positive tap test: refer to neurosurgery for placement of a ventriculoperitoneal shunt, which is the definitive treatment for NPH.
- Complications
Shunt malfunction: obstruction, disconnection, or valve failure can cause recurrence of symptoms and requires shunt revision.
- Prognosis
Gait response: gait disturbance is the most shunt-responsive symptom, with many patients showing meaningful improvement within weeks of shunt placement.
- Prevention
No established primary prevention for idiopathic NPH: because the underlying cause of impaired CSF absorption in idiopathic disease is unknown, there is no proven strategy to prevent it.
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