A 68-year-old man develops gait disturbance out of proportion to his cognitive decline, followed by urinary urgency. CT shows enlarged ventricles with sulci preserved. Lumbar puncture opening pressure is 15 cmH2O with normal CSF composition. The diagnosis and expected response to CSF drainage are:
- A Normal pressure hydrocephalus, symptoms improve after serial lumbar punctures or shunting ✓
- B Communicating hydrocephalus from prior meningitis, unresponsive to shunting
- C Hydrocephalus ex vacuo from Alzheimer disease, worsens after shunting
- D Idiopathic intracranial hypertension, improves after acetazolamide
Correct answer: A. Normal pressure hydrocephalus, symptoms improve after serial lumbar punctures or shunting
Explanation
The classic triad of wet, wobbly, and wacky with ventriculomegaly but normal opening pressure defines normal pressure hydrocephalus. It results from impaired CSF absorption despite normal pressure, and removal of 30 to 50 mL of CSF characteristically improves gait before cognition, predicting shunt benefit. Hydrocephalus ex vacuo also shows large ventricles, but it reflects cortical atrophy with widened sulci and does not improve with drainage.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.