SAHIn Wednesday’s post about the Colorado Compendium, Graham mentioned a new 2010 BMJ article on the high-risk signs suggestive of subarachnoid hemorrhage by the gurus in clinical prediction rules in Canada.

We excessively work-up patients for a subarachnoid hemorrhage with a nonspecific headache and no neurologic deficitis. This is because it’s difficult to predict who is high, medium, and low risk for such a bleed. So we throw a wider net so that we don’t miss such a devastating diagnosis. This usually means a CT and LP for many patients with a headache.

In this 5-year multicenter study, the investigators identified clinical decision rules to help identify the higher-risk groups for a subarachnoid hemorrhage. They derived 3 models, based on recursive partitioning. Each has a negative predictive value of 100%.

Before thinking about seeing if your headache patient has any of these high-risk features, pay special attention to see if s/he would have met the inclusion and exclusion criteria of this study.

Inclusion criteria:

  • Neurologically intact adults (age ≥ 16 years) with a non-traumatic headache peaking within an hour.

Exclusion criteria:

  • History of ≥3 recurrent HA’s of same character/intensity
  • Referred from another hospital with confirmed SAH
  • Returned for reassessment of same HA which was already evaluated for SAH
  • Papilledema
  • New focal neurologic deficits
  • Previous dx of cerebral aneurysm or SAH
  • Previous dx of brain neoplasm
  • Known hydrocephalus

Although none of the models are validated as of yet, the cumulative list of clinical characteristics from these 3 models may be able to help you understand who may be at higher risk:

  • Age ≥ 40 years
  • Witnessed loss of consciousness
  • Neck pain or stiffness
  • Onset of HA with exertion
  • Arrival by ambulance
  • Vomiting
  • DBP ≥ 100 mmHg or SBP ≥ 160 mmHg

PV Card: Subarachnoid Hemorrhage – High Risk Characteristics

Adapted from 1
Go to the ALiEM Cards site for more resources.

Perry J, Stiell I, Sivilotti M, et al. High risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: prospective cohort study. BMJ. 2010;341:c5204. [PubMed]
Michelle Lin, MD
ALiEM Editor-in-Chief
Professor and Digital Innovation Lab Director
Department of Emergency Medicine
University of California, San Francisco
Michelle Lin, MD


Professor of Emerg Med at UCSF-Zuckerberg San Francisco General. Founder of ALiEM @aliemteam #PostitPearls
Michelle Lin, MD