• Several conditions cause increased intracranial pressure (ICP), requiring lumbar puncture (LP) with opening pressure (OP) measurement for diagnostic and therapeutic management.

• Examples of such include:  pseudotumor cerebri, (cryptococcal) meningitis, intracranial mass, and intracranial hemorrhage.

• In order to ensure an accurate measurement, OP should be assessed while the patient is in the lateral decubitus position with the neck and legs in a neutral position.

• Normal OP ranges from 10 to 100 mm H₂0 in children, 60 to 200 mm H₂0 after age 8, and up to 250 mm H₂0 in the obese.  OP > 250 = intracranial hypertension.

• OP (the meniscus level) can fluctuate by 2 to 5 mm H20 with patient's pulse and by 4 to 10 mm H20 with patient's respirations.

• A patient's symptoms of headache and/or neurologic deficit is often relieved by lowering the ICP through slow removal of CSF during LP.  The pressure level should not be lowered by any more than 50% of the initial OP.

References

1. Conly JM, Ronald AR. Cerebrospinal fluid as a diagnostic body fluid. Am J Med 1983;75(1B):102-8.
2. Fishman RA. Cerebrospinal fluid in diseases of the nervous system. 2d ed. Philadelphia: Saunders, 1992.
3. Lyons MK, Meyer FB. Cerebrospinal fluid physiology and the management of increased intracranial pressure. Mayo Clin Proc 1990;65:684-707.