Synopsis
Recognise gait-led possible normal-pressure hydrocephalus, interpret ventriculomegaly in clinical context, and use objective drainage testing and neurosurgical selection rather than the triad alone.
- Idiopathic normal-pressure hydrocephalus is a chronic syndrome of gait dysfunction, cognitive impairment and urinary symptoms associated with communicating ventriculomegaly and potentially responsive to CSF diversion.
- Gait impairment is usually earliest and most prominent: short shuffling steps, broad base, poor initiation, freezing and difficulty turning despite relatively preserved leg power.
- Cognition often shows psychomotor slowing, reduced attention and executive dysfunction rather than the isolated early encoding failure typical of Alzheimer disease.
- Urinary urgency and frequency generally precede incontinence; faecal incontinence is late and non-specific and should not be used to complete a textbook triad.
- Ventriculomegaly alone is common with cerebral atrophy; imaging must assess whether ventricular enlargement is disproportionate and whether alternative structural disease exists.
- An Evans index above 0.3 supports ventriculomegaly but is not diagnostic; callosal angle and disproportionately enlarged subarachnoid-space features can add specialist context.
- Use timed gait measures before and after a large-volume lumbar tap or external drainage when selecting for shunt; subjective recollection is less reliable.
- Failure to improve after one tap reduces confidence but does not absolutely exclude shunt responsiveness, particularly when phenotype and imaging are strong.
- Ventriculoperitoneal shunting can improve gait most reliably, but infection, subdural collection, overdrainage, obstruction and revision risk require careful shared selection.
Key red flags
Rapid headache, vomiting, drowsiness, papilloedema or focal change is not idiopathic NPH and requires emergency imaging for acute pressure or another intracranial event.
Investigation priorities
Characterise the gait syndrome and create objective baseline measures for drainage testing and postoperative review.
Management branches
Progressive initiation and turning difficulty occurs with cognitive slowing or urinary urgency.
- Observe gait directly and record onset order, falls, aids, parkinsonian signs, pyramidal features, sensation and spinal symptoms.
- Obtain collateral cognitive and bladder history, review medicines and screen common metabolic, urological and neurodegenerative alternatives.
- Arrange structural brain imaging and compare ventricular size with sulci and CSF pathways rather than reporting ventriculomegaly in isolation.
- Refer a coherent gait-led phenotype to a specialist hydrocephalus or neurosurgical pathway before disability becomes irreversible.