October 24, 2018

Background: Headache is a common presentation to the emergency department  (ED) accounting for 2% of all visits [1].  Of the patients that present with headache,1 – 3% will be due to a subarachnoid hemorrhage (SAH) [1]. SAH is a true diagnostic dilemma as delays in diagnosis can lead to significant morbidity and mortality. Further complicating matters, almost half of patients will be alert and neurologically intact at first presentation [3].  Non-Contrast Head CT (NCHCT) is very sensitive when performed soon after headache. However, we don’t want to order unnecessary NCHCTs as that increase cost and radiation exposure. Invasive testing such as lumbar puncture, which in itself can be a painful procedure, can also cause headache.  The Ottawa SAH Clinical Decision Rule was designed to help facilitate the identification of SAH in alert, neurologically intact adults presenting to the ED with acute, non-traumatic headache, while minimizing expensive and invasive over testing.  This post will serve as a review of the current literature in the derivation and validation of the Ottawa SAH Clinical Decision Rule.

February 11, 2016

Background: Headache accounts for approximately 2% of all ED visits. One of the most serious etiologies of headache is aneurysmal subarachnoid hemorrhage (SAH), which accounts for 4 – 12% of ED patients with thunderclap headache. There have been several studies in the past few years suggesting that in neurologically intact patients, the sensitivity of modern CT scanners for SAH approaches 100% if performed within 6 hours of headache onset and interpreted by qualified radiologists. If true this data suggests that an LP may not be necessary to rule out SAH and an initial negative CT can be considered a rule-out test.

January 25, 2016

Background: Although non-contrast head CT (NCHCT) has near perfect sensitivity (98-100%) in detecting aneurysmal subarachnoid hemorrhage (SAH) when performed within 6 hours of headache onset, sensitivity declines after 6 hours. As a result of declining sensitivity, lumbar puncture (LP) continues to be part of the workup in suspected SAH. An LP gives providers the ability to perform CSF analysis for red blood cells and detect xanthochromia by visual inspection or spectrophotometry. In most of the world, including the United States, the predominant approach to identifying xanthochromia is visual detection. However, this technique is subjective and considered unreliable by many. Spectrophotometry is a more objective test but, has lower specificity, carries a higher cost and is unavailable in the majority of hospitals. In patients with SAH diagnosed by NCHCT or suspected based on LP results, angiography (CTA or MRA) is typically performed to investigate for an aneurysm that requires neurosurgical intervention. Angiography is considered to be the “gold standard” test for looking for aneurysmal SAH although it is not without it’s own limitations (a small minority of the population will have benign aneurysms and these increase with age).

January 7, 2016

Background: The traditional standard workup for ruling out subarachnoid hemorrhage (SAH) has been a non-contrast head CT and, if negative, a lumbar puncture. The thought behind this is that the sensitivity of head CT to rule out SAH is not 100% and declines over time and missing a SAH is potentially devastating. There has been a series of studies published in the past few years looking at the value of a negative head CT scan performed within 6 hours of headache onset in ruling out SAH. I have heard many say that if they have a negative Head CT at 6 hours or less in a neurologically intact patient they would not perform a lumbar puncture.