title: Controversies in the Diagnosis of Subarachnoid Hemorrhage.
abstract: BACKGROUND
  Headache is a common chief complaint in emergency departments, accounting for 2% of visits, and subarachnoid hemorrhage (SAH) is a life-threating cause of headache. This deadly disease is most commonly due to aneurysmal rupture. Various approaches exist for diagnosis, with recent studies evaluating these approaches. A great deal of controversy exists about the optimal diagnosis strategy for SAH.
  
  
  OBJECTIVE
  This article in the Best Clinical Practice Series seeks to educate emergency physicians on the recent literature in the diagnosis of SAH and provide an evidence-based approach.
  
  
  CONCLUSIONS
  Various diagnostic strategies exist, including use of noncontrast head computed tomography (CT) alone, CT/lumbar puncture (LP) in combination, CT/CT angiography, and magnetic resonance imaging/magnetic resonance angiography. The use of clinical decision rules has also been espoused, and several contemporary studies have evaluated cerebrospinal fluid results of red blood cell count and xanthochromia in the diagnosis of SAH. Recent literature supports that a negative head CT done within 6 h of headache onset places the patient at a < 1% risk for SAH. With the complex literature, a shared decision-making model should be followed with options, risks, and benefits discussed with the patient.
  
  
  CONCLUSIONS
  Literature support exists for all of the diagnostic strategies. The American College of Emergency Physicians Clinical Policy supports CT and LP for definitive diagnosis. Risk stratification and a shared decision-making model with the patient should be followed, and a negative head CT within 6 h of headache onset places patient at a risk of < 1% for having SAH.
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, Fort Sam Houston, Texas.
authors.forename: Brit
authors.initials: B
authors.lastname: Long
authors.affiliation: Department of Emergency Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Alex
authors.initials: A
authors.lastname: Koyfman
mesh_terms: D003657:Decision Making; D004636:Emergency Service, Hospital / Q000458:organization & administration; D017408:Guidelines as Topic; D006261:Headache / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000592:standards; D012307:Risk Factors; D013129:Spinal Puncture / Q000379:methods / Q000592:standards; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards; D014474:Unconsciousness / Q000209:etiology; D014839:Vomiting / Q000209:etiology
keywords: head computed tomography; lumbar puncture; subarachnoid hemorrhage; xanthochromia