In VP shunt management, which statement is true about overdrainage?

• A. Overdrainage is protective against subdural hematoma.
• B. Infection is the only concern.
• C. Underdrainage causes subdural hematoma.
• D. Overdrainage can cause subdural hematomas.

Answer: (D)

Overdrainage lowers intracranial pressure by removing CSF faster than it’s produced, and the siphon effect with upright posture can pull CSF out of the ventricles. This causes brain sagging and stretching of the bridging veins, which can tear and lead to subdural hematomas (or hygromas). That’s why overdrainage can cause subdural hematomas—the risk arises from the mechanical effect of too-fast CSF removal, not from infection or prevention of bleeding. The other statements aren’t correct: overdrainage isn’t protective against subdural hematoma, infection isn’t the only concern, and underdrainage doesn’t classically cause subdural hematomas. In practice, preventing overdrainage with appropriate valve settings or anti-siphon devices helps minimize this risk.