Subarachnoid Hemorhage

Dr. Holly Ryan

Editor: Omar Lopez MS3


1. Headache is a very common complaint in the ED, up to 2% of patients that walk into the emergency department have the CC of HA.

2. SAH is a stroke

  3. Patient Population has a broad age range 

4.  Life-threatening and can be fatal.





Presentation Work-Up

Buzzwords: thunderclap headache, worst HA of my life

Signs & Symptoms: 

ACEP Clinical Guidelines and Policies

1. Risk stratification for emergent imaging in ED patients with headache?

2. Further workup necessary in adult ED patient with normal noncon CT Head within 6 hours of HA onset?

3. Is CTA as effective as LP to r/o SAH?

Lumbar Puncture

CT Angiography





Literature Review

Objective: To measure the sensitivity of modern third generation computed tomography in emergency patients being evaluated for possible subarachnoid haemorrhage, especially when carried out within six hours of headache onset.

Design: Prospective cohort study.

Setting: 11 tertiary care emergency departments across Canada, 2000-9.

Participants: Neurologically intact adults with a new acute headache peaking in intensity within one hour of onset in whom a computed tomography was ordered by the treating physician to rule out subarachnoid haemorrhage.

Main outcome measures: Subarachnoid haemorrhage was defined by any of subarachnoid blood on computed tomography, xanthochromia in cerebrospinal fluid, or any red blood cells in final tube of cerebrospinal fluid collected with positive results on cerebral angiography.

Results: Of the 3132 patients enrolled (mean age 45.1, 2571 (82.1%) with worst headache ever), 240 had subarachnoid haemorrhage (7.7%). The sensitivity of computed tomography overall for subarachnoid haemorrhage was 92.9% (95% confidence interval 89.0% to 95.5%), the specificity was 100% (99.9% to 100%), the negative predictive value was 99.4% (99.1% to 99.6%), and the positive predictive value was 100% (98.3% to 100%). For the 953 patients scanned within six hours of headache onset, all 121 patients with subarachnoid haemorrhage were identified by computed tomography, yielding a sensitivity of 100% (97.0% to 100.0%), specificity of 100% (99.5% to 100%), negative predictive value of 100% (99.5% to 100%), and positive predictive value of 100% (96.9% to 100%).

Conclusion: Modern third generation computed tomography is extremely sensitive in identifying subarachnoid haemorrhage when it is carried out within six hours of headache onset and interpreted by a qualified radiologist.

Results: 91% of cases had a completely negative LP with absolutely no xanthochromia present. Only 4% were positive and 5% were equivocal. Completed CT angiography in the positive or equivicol patient population and found that only 4% had a cerebral aneurysm. Which led to conclude that in suspected SAH cases where CT scan in negative, the rate of detection for cerebral aneurysm with LP is 0.4%.

Management and Disposition


DISPO = ICU, neurosurgery

Controversies in Care: Seizure PPX

Increased risk: