Safety of care

Improving patient safety and reducing risks

When diagnosing subarachnoid hemorrhage, consider the possibilities

An article for physicians by physicians
Originally published March 2011

You are evaluating a 50-year-old male with a history of hypertension and nicotine dependence who noted the abrupt onset of a severe headache while playing squash. He volunteers that the headache is the worst he has ever experienced and also reports a transient episode of loss of consciousness, vomiting, and sensitivity to light. The physical exam reveals the presence of moderate nuchal rigidity, but there are no focal neurological findings. A brain CT scan reveals blood in the subarachnoid space.

Early diagnosis of subarachnoid hemorrhage (SAH) is important as early surgical or radiological intervention may reduce short-term complications such as cerebral vasospasm and rebleeding. However, even when patients present with symptoms typical of SAH, such as those described above, a diagnosis of SAH may sometimes be delayed.

In a review of its medico-legal cases involving SAH that closed between 1998 and 2010, and any that are currently open, the CMPA identified 44 cases of which 30 (68%) were legal actions. The remaining 14 were medical regulatory authority (College) complaints, hospital complaints, or threats.

The review reveals three recurring problem areas:

  1. Not considering the diagnosis.
  2. Difficulties or delays in obtaining, interpreting, or reporting diagnostic imaging.
  3. Not pursuing further investigations in situations where the clinical index of suspicion is high but initial investigations are negative.

Key points

When evaluating patients with acute headache, the following observations may be pertinent:

  1. The medical record should document, among other things, both the response to the therapy and timely reassessments.
  2. Courts view the formulation and documentation of a differential diagnosis as evidence of a physician's competence, prudence, and thoughtfulness.

Case: An atypical migraine

The following case illustrates a misstep in the diagnostic process.

At 1300 hours on a weekend afternoon, a 47-year-old female nurse with a past history of migraine headache was transported by ambulance to the emergency department of a community hospital. Her chief complaint was a headache of sudden onset without her usual preceding aura.

She noted visual disturbances, described as rainbows, which occurred simultaneously with the onset of the headache. The headache was diffuse, pounding in nature, and associated with mild photophobia, nausea, and multiple episodes of vomiting. The severity was described as being equal to her worst migraine. The ambulance report documented that the patient described her headache as "her worst ever." The presenting vital signs were normal. She was assessed by emergency physician A within 15 minutes of arrival. A detailed neurological examination including fundoscopy, assessment for meningeal signs, and motor function was normal. A review of her hospital chart revealed no previous visits to that emergency department for migraines. The initial diagnostic impression was complex migraine.

During the ensuing two hours she received the following intravenous medications in doses: dihydroergotamine (DHEA) 1.0 mg, metoclopramide (Maxeran) 20 mg, dimenhydrinate (Gravol) 50 mg, and chloropromazine 25 mg. Allergies or sensitivities to morphine, meperidine (Demerol), and prochlorperazine (Stemetil) precluded their use. At 1600 hours, the patient was noted to be drowsy but rousable. Based on this observation, physician A inferred that her pain had diminished. At 1630 hours the patient was discharged with a prescription for acetaminophen with an oral analgesic. Neither a clinical reassessment nor discharge instructions were documented at the time of discharge.

Six days later the patient returned to the emergency department with ongoing intermittent severe headaches associated with nausea and vomiting. Vital signs were normal except for a BP of 175/110 mm Hg. She was assessed by emergency physician B who documented that this was a typical migraine. Neurological examination was unremarkable. Metoclopramide and dimenhydrinate were administered intravenously. Two hours after admission, the patient stated her headache had almost completely resolved. She was discharged with instructions to follow up with her family physician.

Twenty-four hours after discharge, she was brought back to the emergency department with a Glasgow Coma Score (GCS) of 13/15 and a left hemiparesis. Physician B assessed her again. A CT scan showed subarachnoid blood and a mild hydrocephalus. She was transferred to a tertiary care centre for assessment by a neurosurgeon. An angiogram later that day showed diffuse vasospasm but no identifiable aneurysm. A lumbar puncture demonstrated xanthochromia. Medical management for vasospasm was initiated. A repeat angiogram three days later showed a small aneurysm of the anterior communicating artery which was subsequently clipped. Despite an aggressive rehabilitation program the patient was left with significant cognitive and motor impairment.

Litigation was commenced a year later. Counsel for the plaintiff (patient) obtained an expert report from an emergency physician practising in a community hospital. While acknowledging that the decision to order diagnostic imaging for a known migraine patient is a difficult one, the expert made the following comments:

The plaintiff's expert was critical of physician A for: 

  • Minimizing the significance of the abrupt onset of the headache.
  • Failing to characterize the nature of the patient's previous migraines with respect to the aura, location, and intensity.
  • Not clarifying whether the patient had ever previously sought treatment in an emergency department.  
  • Inferring the patient's drowsiness after large doses of intravenous sedative agents indicated a reduction in the intensity of the headache.
  • Inferring that a favourable response to migraine treatment made the diagnosis more likely.
  • Not documenting either a reassessment or the discharge instructions.

The plaintiff's expert was critical of physician B for:

  • Assuming prematurely that this was a "typical migraine."
  • Not adequately characterizing the nature and frequency of the patient's symptoms over the previous six days.
  • Assuming that the response to medication excluded a more sinister diagnosis.
  • Not considering emergency diagnostic imaging in this case.

Expert support for both physicians was sought, but unqualified support for the defence could not be obtained. On this basis, the CMPA made a settlement to the patient on behalf of both physicians.

In hindsight, it appears that both physicians A and B firmly anchored to the diagnosis of migraine early in the clinical encounter without entertaining other possible etiologies. The initial diagnosis of migraine appears to have carried some momentum into the second clinical assessment.

Identifying risk

In this case, experts identified the following risk management considerations:

  • The sudden onset of, and the absence of, the usual aura argued against the diagnosis of typical migraine.
  • Clarification of the frequency of emergency visits for rescue medications would have been a useful surrogate marker for headache severity.


DISCLAIMER: The information contained in this learning material is for general educational purposes only and is not intended to provide specific professional medical or legal advice, nor to constitute a "standard of care" for Canadian healthcare professionals. The use of CMPA learning resources is subject to the foregoing as well as the CMPA's Terms of Use.