What is the normal opening pressure range for cerebrospinal fluid in adults?

• A. 50–100 mm H2O
• B. 70–180 mm H2O
• C. 60–140 mm H2O
• D. 200–300 mm H2O

Answer: (B)

Opening pressure of cerebrospinal fluid is the measurement taken at the start of a lumbar puncture to assess intracranial pressure. In adults, the normal range is about 70–180 mm H2O (roughly 7–18 cm H2O). This value can vary a bit depending on how the procedure is done and the patient’s position, but 70–180 mm H2O is the standard reference range. Values higher than this suggest increased intracranial pressure, which can occur with mass effect, hydrocephalus, or meningitis with raised ICP; lower values may indicate CSF leakage, dehydration, or other conditions reducing CSF pressure. Among the options, 70–180 mm H2O best matches this established normal range, while the others are either too narrow or outside the expected range.