14 Nov Thunderclap Headache: Ottawa Rule To Exclude Subarachnoid Bleeding
MedicalResearch.com Interview with:
Jeff Perry, MD, MSc, CCFP-EM
Professor, Department of Emergency Medicine
Senior Scientist, Ottawa Hospital Research Institute
Research Chair in Emergency Neurological Research, University of Ottawa
Emergency Physician and Epidemiology Program
The Ottawa Hospital
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Headache accounts for about 1-2% of all emergency department visits. One of the most feared diagnosis within these patients is subarachnoid hemorrhage. While investigations are clearly warranted for patients with a diminished level of consciousness or new focal neurological deficits, approximately 50% of patients with subarachnoid hemorrhage (SAH) have no focal or global neurological findings. Deciding whether to image headache patients with no deficits is difficult, especially since timely diagnosis and treatment results in substantially better outcomes.
The desire to never miss a subarachnoid hemorrhage, however, contributes to escalating neuroimaging rates and a dogmatic adherence to lumbar puncture, even if the scan is negative, despite the very high sensitivity of computed tomography. However, a recent population-based study suggested that over 5% of confirmed subarachnoid hemorrhages were missed at initial presentation, especially in smaller hospitals. Therefore, identifying which headache patients require investigations to rule-out SAH is of great importance.
We have previously derived (N=1,999) and refined (N=2,131) the Ottawa SAH Rule. In this study, we conducted an multicenter prospective cohort study at six tertiary care hospitals, and found that the Ottawa SAH Rule performed well, with an 100% sensitivity, and specificity of 13.6%.
MedicalResearch.com: What should readers take away from your report?
- Age >=40
- Neck pain or stiffness
- Witnessed loss of consciousness
- Onset during exertion
- Thunderclap headache (instantly peaking pain)
- Limited neck flexion on examination
This headache rule is for neurologically normal patients with a headache which peaks within 1 hour, with no trauma and are not known to have recurrent headaches (i.e. ≥3 similar headaches over a period of greater than 6 months). It is also not intended for patients with brain shunts, known brain tumors or previous subarachnoid hemorrhage. Headache patients with one or more of these high risk clinical variables require investigations for subarachnoid hemorrhage.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Subsequent research will assess how physicians use the Rule in actual clinical practice.
MedicalResearch.com: Is there anything else you would like to add?
Response: We suggest that the initial investigation for subarachnoid hemorrhage to be an unenhanced CT head. If the CT is done within 6 hours, we suggest no further testing for most patients. The optimal method to determine if further testing is to have a shared decision with the patient and their family. The risk of subarachnoid hemorrhage is less than 1% in this early imaging group. Patients deemed to be at exceptionally high risk (i.e. instant headache, age >40 and family history of SAH) may be considered for lumbar puncture (LP). CT should not be relied on in patients known to be moderate to severely anemic, as blood is not well distinguished from cerebrospinal fluid in this population. Patients presenting after 6 hours will need a LP.
We have previously identified that a normal CT and normal LP completely rules out a SAH. For LPs which are not completely normal, we have previously determined that cerebrospinal fluid results with <2000 red blood cells x 109/L and no visual xanthochromia is a low risk tap. Unless patients are at ultra-high-risk, it is reasonable to stop investigating. We recommend CT angiography when an LP is indicated but the patient has contraindications, the patient is a late presenter (i.e. >1 week after headache onset) or they have abnormal CT or high risk LP findings. Indiscriminate CT angiography will increase the number of incidental aneurysms identified (estimated to be present in 3% of the population). Many of these may be either coiled or clipped which may cause unnecessary morbidity or mortality for an aneurysm which would never have caused them harm.
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
Jeffrey J. Perry, Marco L.A. Sivilotti, Jane Sutherland, Corinne M. Hohl, Marcel Émond, Lisa A. Calder, Christian Vaillancourt, Venkatesh Thirganasambandamoorthy, Howard Lesiuk, George A. Wells, and Ian G. Stiell
Validation of the Ottawa Subarachnoid Hemorrhage Rule in patients with acute headache CMAJ November 13, 2017 189:E1379-E1385; doi:10.1503/cmaj.170072
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