Subarachnoid hemorrhage is a rare but potentially catastrophic cause of headache. While headaches are common, patients with subarachnoid hemorrhage typically experience a rapidly peaking and severe headache, often described as a "thunderclap.” They are frequently over 40 years of age and present with other distinct signs and symptoms, such as a brief loss of consciousness, vomiting, and neck pain or stiffness. Healthcare provider and team situational awareness are often key to the effective diagnosis and management of this emergency situation.
The CMPA reviewed 60 medical-legal cases, closed between 2009 and 2019, in which the diagnosis of non-traumatic subarachnoid hemorrhage was alleged to have been missed or delayed. Over half of these cases were legal actions (33 [55%]), followed by regulatory authority (College) complaints (22 [37%]), and hospital investigations (5 [8%]). Reflecting the fact that subarachnoid hemorrhage has a mortality rate approaching 50%,1 death or severe injury was the most common category of patient outcome in these cases. However, slightly more than half of all cases (32 [53%]) had favourable medical-legal outcomes for the members involved. This was likely owing to factors such as atypical presentations, involvement of non-physician healthcare providers that contributed to the negative patient outcome, and expert opinion stating that misdiagnosis did not affect the patient’s outcome. The specialties most commonly involved were family or emergency medicine physicians (48 [59%]), neurosurgeons or neurologists (15 [18%]), and radiologists (6 [7%]). Five cases (6%) involved a resident.
Diagnosis of subarachnoid hemorrhage can be challenging, and one study found that about one in 20 patients are misdiagnosed during their first assessment in the emergency department (ED).2 According to CMPA data, diagnostic error occurred in 39 of 60 subarachnoid hemorrhage cases. In the remainder of these cases peer experts determined that the standard of care in reaching a diagnosis had been met.
Contributing factors in diagnostic error cases
A major theme in cases with diagnostic error was patients presenting on more than one occasion with the same or worsening symptoms (22/39 cases). These return visits can present opportunities for reassessing these patients and potentially identifying cognitive biases or broadening the differential diagnosis. Records from recent visits to other healthcare professionals might also point to a potentially missed subarachnoid hemorrhage diagnosis.
Clinical decision-making in subarachnoid hemorrhage
As expected, diagnostic error most often concerned the physician’s clinical decision-making process. Examples included the following: not ordering the appropriate investigations for a patient presenting with symptoms consistent with subarachnoid hemorrhage, such as severe headache accompanied by vomiting or neurological symptoms; and failing to reconsider the differential diagnosis when a patient returns with the same complaint. Some physicians anchored on another cause for the patient’s symptoms, such as neck muscle strain. Indeed, the risk of cognitive biases such as anchoring can be elevated in a busy emergency department.
Close to one-third of cases (28%) involved a lack of situational awareness, including choosing observation over immediate investigation when subarachnoid hemorrhage was high in the differential diagnosis. Research shows that unenhanced CT is highly sensitive in identifying subarachnoid hemorrhage when performed within six hours of the headache’s onset, after which time imaging alone can be less reliable.3 Decision support tools such as the Ottawa Subarachnoid Hemorrhage Rule4, 5 can aid in situational awareness and in evaluating the need for further investigation for certain patients who present with sudden onset headache.
Case example: Return visit offers opportunity to reassess
A woman in her 60s arrives by ambulance at the ED with severe occipital pain. It is the second time she has attended this ED in the last three days. The pain first occurred while she was doing heavy yard work and returned during physical activity two days later. On her first visit, the ED physician who examined her suspected that her pain was musculoskeletal and administered an opioid analgesic before eventually discharging her.
On the second visit, the patient rates her pain at 6 out of 10 and tells the ED physician that she vomited twice the previous day and has since felt nauseated. She has a history of chronic neck pain from an old injury. During the physical examination, the physician finds no neurological deficit or photophobia. Mindful of the fact that the patient also complains of an acute increase in her chronic neck pain, the physician notes tenderness along the patient’s trapezius to the occiput, but no neck stiffness. The patient is given IV fluids, ketorolac, and metoclopramide. The patient begins to feel better, with only minor residual occipital pain. The ED physician discharges the patient with instructions to see her family physician within a few days and to try massage therapy for her neck pain. She is also advised to return immediately if her headache does not improve or if she develops new symptoms.
A few days later, the patient, still unwell, attends at another ED. Here, she receives a CT scan that shows evidence of a subarachnoid hemorrhage. The patient is immediately transferred to another facility where she undergoes coiling of a cerebral artery aneurysm. The patient recovers but is left with right-sided weakness. The patient files a College complaint alleging that, on her second visit to the ED the physician failed to diagnose the subarachnoid hemorrhage. The College committee cautions this physician that when a patient returns to the ED with a persistent or worsening headache, the physician should focus on ruling out the possibility that it could be a serious condition such as a subarachnoid hemorrhage.
Diagnosis and coordination of care
Communication and coordination of care was an issue in 11 of the 39 diagnostic error cases (28%). These situations included return visits to different facilities or providers, resulting in a lack of coordination of care; miscommunication between providers, including issues related to the follow-up of imaging results; triage issues that led to delayed assessment of patients in the ED; and other breakdowns in communication between providers and with patients. Coordination of care can be influenced by system issues such as crowded EDs, lack of procedures for flagging or communicating urgent results, and the unavailability of diagnostic imaging. These challenges highlight the importance of coordination of care and team situational awareness when diagnosing and managing subarachnoid hemorrhage, especially in resource-constrained environments.
The bottom line
Although subarachnoid hemorrhage is an uncommon cause of severe headache, it is a medical emergency that carries a high mortality rate. A return visit for the same or worsening complaint—present in over half of CMPA diagnostic error cases—sometimes offers a second chance to avoid a potentially catastrophic outcome. Individual provider and team situational awareness, which can be enhanced with clinical decision support tools, are key to effective diagnosis and management of non-traumatic subarachnoid hemorrhage.
- Singer RJ, Ogilvy CS, Rordorf G. Clinical manifestations and diagnosis of aneurysmal subarachnoid hemorrhage. UpToDate.com [Internet]. 2017 Nov 1 [cited on 2019 May 24]. Available from: https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-aneurysmal-subarachnoid-hemorrhage.
- Vermeulen MJ, Schull MJ. Missed diagnosis of subarachnoid hemorrhage in the emergency department. Stroke. 2007 Apr;38(4):1216-21. Epub 2007 Feb 22
- Perry JJ, Stiell IG, Sivilotti ML, et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011;343:d4277.a
- Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013 Sep 25;310(12):1248-55. doi: 10.1001/jama.2013.278018
- Perry JJ, Sivilotti MLA, Sutherland J, et al. Validation of the Ottawa Subarachnoid Hemorrhage Rule in patients with acute headache. CMAJ. 2017 Nov 13;189(45):E1379-85