Scenario: The images from your patient’s non-contrast head CT are finally uploaded and it looks negative. Unfortunately, your patient has been having severe symptoms for almost 24 hours and you know this single study is not sensitive enough to rule-out a SAH. Have you ever informed your patient about the need for LP and have him or her steadfastly refuse? Have you ever then looked at your patient with a BMI of 40 at 3pm on a Monday when you have several other critically ill patients to care for and thought it is not in the best interest of any of your patients to attempt an LP at this time?

How would you proceed? Perhaps this is an appropriate case to employ shared decision making and discuss the option of CT angiography in place of an LP. The sensitivity of CTA following NCHCT for SAH is reported to be greater than 99%. While there are drawbacks to CT angiography of the brain (radiation exposure, incidental discovery of benign aneurysms), this alternative paradigm can offer patients a painless, non-invasive approach to ruling-out SAH that they might prefer.

References:

1) McCormack RF, Hutson A. “Can computed tomography angiography of the brain replace lumbar puncture in the evaluation of acute-onset headache after a negative non contrast cranial computed tomography scan?” Acad Emerg Medicine. 2010; 17: 444-451

2) Probst, Marc & Hoffman, Jerome. “Computed Tomography Angiography of the Head Is a Reasonable Next Test After a Negative Noncontrast Head Computed Tomography Result in the Emergency Department Evaluation of Subarachnoid Hemorrhage” Annals of Emergency Medicine. June 2016 Volume 67, Issue 6, Pages 773–774