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Normal-pressure hydrocephalus — ABIM Board MCQ

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HardNeurologyNormal-pressure hydrocephalusABIM Board

A 74-year-old man has gait initiation failure, urinary urgency, cognitive slowing and ventriculomegaly out of proportion to cortical atrophy. Before committing to shunt surgery, which test most directly estimates the likelihood of gait benefit?

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Correct answer: C — Perform a large-volume CSF tap with standardized timed gait assessment

The best answer is “Perform a large-volume CSF tap with standardized timed gait assessment”. Objective improvement in timed gait measures after removal of a substantial CSF volume supports shunt responsiveness in suspected normal-pressure hydrocephalus. A negative single tap does not absolutely exclude benefit, and prolonged external lumbar drainage may be considered when suspicion remains high, but the listed alternatives do not test CSF-responsive gait physiology.

Reference: AAN Practice Guideline: Idiopathic Normal Pressure Hydrocephalus: https://pmc.ncbi.nlm.nih.gov/articles/PMC4676757/