Cerebral perfusion pressure is calculated as which difference?

• A. MAP minus ICP
• B. ICP minus MAP
• C. MAP plus ICP
• D. MAP times ICP

Answer: (A)

Cerebral perfusion pressure is the pressure gradient that drives blood flow to the brain. It is calculated as mean arterial pressure minus intracranial pressure. MAP provides the arterial driving force, pushing blood into the brain, while ICP represents the pressure inside the skull that resists that inflow. The difference between the two determines how well blood can reach brain tissue. If ICP rises or MAP falls, CPP drops and brain perfusion can be compromised, potentially leading to ischemia. Conversely, increasing MAP raises CPP, up to limits set by autoregulation.

The other options don’t reflect a pressure gradient that drives perfusion: subtracting MAP from ICP would yield negative values most of the time, and adding or multiplying the pressures doesn’t describe the driving force for blood flow.