How is cerebral perfusion pressure (CPP) calculated?

• A. ICP minus MAP
• B. MAP minus ICP
• C. CPP equals mean arterial pressure
• D. MAP plus ICP

Answer: (B)

Cerebral perfusion pressure is the pressure gradient that drives blood flow to the brain. It is determined by the difference between mean arterial pressure (MAP) and intracranial pressure (ICP). So the calculation is CPP = MAP − ICP.

If ICP increases, that gradient shrinks and cerebral blood flow can drop, risking ischemia. Conversely, increasing MAP or reducing ICP enlarges the gradient, improving perfusion (within safe limits). In practice, clinicians aim for a CPP typically around 60–70 mmHg in adults to maintain adequate brain perfusion, using methods to raise MAP or lower ICP as needed. The other formulations don’t reflect the actual driving pressure: subtracting ICP from MAP would misrepresent the gradient, and using MAP alone or adding the two pressures does not yield the perfusion pressure driving cerebral blood flow.