Normal pressure hydrocephalus
Description
- Communicating hydrocephalus with ventriculomegaly and a normal CSF opening pressure, producing a characteristic triad
- "Normal pressure" is a misnomer - pressure fluctuates with intermittent B-wave elevations; it is simply normal at the moment you measure it
The triad - "wet, wacky, wobbly"
| Feature | Detail | |
|---|---|---|
| 1. Gait | Gait apraxia/ataxia - FIRST and most responsive | Magnetic, "feet stuck to the floor", wide-based, short shuffling steps, en-bloc turning, reduced step height with preserved arm swing |
| 2. Cognition | Subcortical frontal pattern | Psychomotor slowing, apathy, inattention, executive dysfunction. Memory storage relatively preserved - cueing helps, unlike Alzheimer |
| 3. Continence | Urinary urgency -> frequency -> incontinence | Appears last; indifference to incontinence is a late frontal sign |
- Gait comes first, responds best and responds most quickly. If gait is not affected, question the diagnosis
- Full triad present in only a minority at diagnosis
- No headache, no papilloedema, no reduced consciousness - those indicate raised pressure and a different diagnosis
Types
- Idiopathic (iNPH) - the classic elderly presentation
- Secondary - after subarachnoid haemorrhage, meningitis, head injury, intracranial surgery; younger, clearer cause, better shunt response
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