What is the normal intracranial pressure range in adults?

• A. Approximately 5 to 15 mmHg.
• B. Approximately 30 to 40 mmHg.
• C. Approximately 0 to 5 mmHg.
• D. Approximately 20 to 25 cm H2O.

Answer: (A)

The main idea here is understanding what level of pressure inside the skull is considered normal in an adult. Intracranial pressure (ICP) stays within a tight range because it balances brain tissue, cerebrospinal fluid, and cerebral blood volume. In healthy adults, the baseline ICP is about 5 to 15 mmHg. Small, normal fluctuations occur with breathing and posture, but values outside this range guide us toward concern: sustained pressures above roughly 20 mmHg indicate intracranial hypertension and risk of impaired brain perfusion or herniation, requiring intervention.

If a reading falls in the 30–40 mmHg range, that is clearly elevated and unsafe, needing urgent evaluation. A value of 0–5 mmHg is unrealistically low for a normal adult and would suggest either over-drainage, measurement artifact, or other issues rather than a true baseline. The option expressed as 20–25 cm H2O translates to about 14–18 mmHg, which is at the upper end of normal or slightly above, depending on the source; it is not considered a normal baseline in most references.

So, the normal adult ICP range is approximately 5 to 15 mmHg.