Definition

A form of chronic communicating hydrocephalus that primarily affects adults > 60 years of age
Characterized by a distinct clinical triad (gait apraxia, dementia, and urinary incontinence) and normal or only mildly elevated ICP

Etiology

Idiopathic (iNPH, most common in adults > 60 years of age)

↓ CSF absorption → CSF accumulation → enlargement of the ventricle → stretching the descending cortical fibers (corona radiata) and compression of cortex and basal ganglia
ICP: normal or only mildly elevated because ventricular dilation compensates for the slow accumulation of CSF

A classic triad of:

Gait abnormalities: frequent falls, broad-based gait with short shuffling steps (gait apraxia, also known as magnetic gait)
Dementia: short attention span, loss of motivation, disturbances of spatial orientation
Urinary incontinence

Tip

Normal pressure hydrocephalus does not manifest with signs of increased ICP (e.g., headache, papilledema).

Mnemonic

Patients present with the classic triad of the 3 Ws: Wet (urinary incontinence), Wacky (dementia), and Wobbly (gait apraxia).

Definitive / First-line: Surgical CSF Diversion (Ventriculoperitoneal [VP] Shunt).
- Indicated in pts with classic clinical triad, supportive MRI, and positive response to high-volume CSF tap test.
- Gait improves the most; dementia is least likely to fully reverse.
Second-line / Alternative:
- Ventriculoatrial (VA) or Ventriculopleural Shunt: Used if VP shunt is contraindicated (e.g., extensive abdominal adhesions, recurrent peritonitis).
Refractory / Non-Surgical Candidates:
- Physical therapy, fall prevention measures, timed voiding/urinary catheterization.
- Note: Serial therapeutic LPs are not recommended long-term due to infection risk and transient relief.
Acetazolamide has no effect because its mechanism is to decrease CSF production, whereas the problem in NPH is impaired CSF absorption. c

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