Normal intracranial pressure ranges from

• A. 5 to 15 mm Hg
• B. 10 to 20 mm Hg
• C. 0 to 5 mm Hg
• D. 15 to 25 mm Hg

Answer: (A)

Normal intracranial pressure is the pressure inside the skull that keeps brain tissue, blood, and CSF in balance to maintain adequate cerebral perfusion. For adults, this normal range is about 5 to 15 mmHg. Keeping ICP in this window helps ensure cerebral perfusion pressure stays sufficient; CPP is mean arterial pressure minus ICP, so when ICP is within 5–15 mmHg, perfusion to the brain remains adequate. If ICP rises toward the higher end of normal or above (commonly considered elevated above about 20 mmHg), CPP can fall and brain tissue may become ischemic or at risk for herniation. Very low pressures (near 0–5 mmHg) are not typical baseline values and can indicate abnormal conditions or measurement issues, while ranges like 15–25 mmHg indicate intracranial hypertension and are not normal.