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