Normal Pressure Hydrocephalus Medical Slides

Describe the procedure: remove 30-50 mL of CSF and assess gait (timed 10-meter walk, TUG test) before and at 1, 4, and 24 hours after drainage. A positive response (>20% improvement in gait speed) has high positive predictive value (73-100%) for shunt response but poor negative predictive value (42-54%). This means a negative tap test does not rule out NPH, and extended lumbar drainage (150-200 mL over 72 hours) should be considered in clinically suspicious cases.

Teach the DESH (disproportionately enlarged subarachnoid-space hydrocephalus) pattern: ventriculomegaly (Evans index >0.3) with tight high-convexity sulci but widened Sylvian fissures, callosal angle <90° on coronal MRI. This contrasts with ex vacuo ventriculomegaly of atrophy, where sulci are proportionally enlarged throughout. MRI CSF flow studies showing elevated aqueductal stroke volume (>42 μL/cycle) provide additional supportive evidence.

Present realistic outcome expectations: 60-80% of well-selected patients improve, with gait showing the best and most durable response, cognition showing moderate improvement (especially attention and processing speed), and urinary symptoms showing the least consistent improvement. Complication rates include shunt malfunction (20-30% over 5 years), subdural hematoma (2-17%), and infection (3-6%). Programmable valves allow non-invasive pressure adjustment and have reduced revision rates.