A 70-year-old man presents with progressive gait apraxia, urinary incontinence, and cognitive decline over 6 months. MRI shows enlarged ventricles with transependymal edema and a callosal angle of 45 degrees on coronal view. What is the most appropriate diagnostic test to predict shunt responsiveness?
- A Lumbar puncture with removal of 30-50 ml CSF (tap test) ✓
- B Intracranial pressure monitoring for 24 hours
- C Radionuclide cisternography
- D CT perfusion study
Correct answer: A. Lumbar puncture with removal of 30-50 ml CSF (tap test)
Explanation
Normal pressure hydrocephalus (NPH) presents with the classic triad of gait apraxia, dementia, and urinary incontinence. The CSF tap test, removing 30-50 ml via lumbar puncture with pre- and post-assessment of gait, is the best predictor of shunt responsiveness. Improvement in gait after the tap predicts favorable outcome of ventriculoperitoneal shunting. Radionuclide cisternography has poor predictive value and is not recommended routinely.
Reference: Bailey and Love's Short Practice of Surgery, 28th ed.
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Written and medically reviewed by the StethoPrep medical team.