A 68-year-old man develops a magnetic gait disturbance, urinary urgency, and progressive slowness of thought over six months. MRI shows ventricles enlarged out of proportion to sulcal atrophy. Lumbar CSF opening pressure is 14 cmH2O. The most likely diagnosis is:
- A Alzheimer disease
- B Vascular parkinsonism
- C Normal pressure hydrocephalus ✓
- D Idiopathic intracranial hypertension
Correct answer: C. Normal pressure hydrocephalus
Explanation
The classic triad of gait apraxia, urinary incontinence, and dementia with enlarged ventricles and normal opening pressure defines normal pressure hydrocephalus, caused by impaired CSF absorption at the arachnoid villi despite free communication between ventricles and subarachnoid space. Gait typically improves first after shunting. Alzheimer disease does not produce disproportionate ventriculomegaly, and IIH presents with raised opening pressure and headache.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.