A 30 year old obese female presents to the emergency department for a persistent headache. You have a high suspicion for idiopathic intracranial hypertension and perform a lumbar puncture. The opening pressure is 28 cm H2O. Approximately how much volume of CSF should be removed to reach a target CSF pressure of 20 cm H2O prior to removal of the spinal needle?
A: 4 mL
B: 8 mL
C: 16 mL
D: 20 mL
Answer: 8 mL
Part of the diagnostic criteria for idiopathic intracranial hypertension in adults includes an elevated opening pressure > 25 cm H2O on lumbar puncture. The feared complication is permanent vision loss from papilledema. Treatment includes removal of CSF which can also provide relief of headache symptoms. As a general rule, removal of 1 mL of CSF will lower the CSF pressure by about 1 mL H2O. It is recommended to remove the desired amount of CSF and then re-measure the CSF pressure prior to removal of the spinal needle. Excess removal of CSF can result in intracranial hypotension and a low pressure headache.
References:
Fiorito-Torres F, Rayhill M, Perloff M: Idiopathic intracerebral hypertension (IIH)/pseudotumor: removing less CSF is best (I9-1.006). Neurology 82 (10 Suppl): I9–1.006, 2014.
Koyfman A, Long B. Headache. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill Education; 2020.
Thurtell, Matthew & Bruce, Beau & Newman, Nancy & Biousse, Valérie. (2010). An Update on Idiopathic Intracranial Hypertension. Reviews in neurological diseases. 7. e56-68. 10.3909/rind0256.
