Headache is one of the most common presenting complaints in Canadian emergency departments. The vast majority of headache presentations have benign or self-limited causes (tension headache, migraine, viral illness, dehydration). A small but important proportion are caused by serious conditions that require urgent diagnosis and intervention (subarachnoid hemorrhage, meningitis, cerebral venous sinus thrombosis, stroke, mass lesions). The framework for distinguishing between the benign and the dangerous causes is one of the most carefully developed areas of emergency medicine. The standard of care turns on careful history-taking, focused examination, and judicious use of investigations. Where the clinical picture is consistent with a benign cause and the warning features for dangerous causes are absent, the framework supports symptomatic management and discharge with return precautions. Where the warning features are present, the framework supports immediate investigation including computed tomography of the head and, in selected cases, lumbar puncture.
Ricottone v Long, 2025 BCSC 1388, released by the Supreme Court of British Columbia on July 21, 2025, is a recent application of the framework. The plaintiff was a 54-year-old man who presented to two different emergency departments in early August 2018 with headache complaints. A CT scan performed during the first visit was negative. At his second presentation three days later, the emergency physician diagnosed a migraine and discharged him with return precautions. Four days after that, the plaintiff returned to the same emergency department with new symptoms, and a subarachnoid hemorrhage was diagnosed. The plaintiff brought an action against the emergency physician from the second visit, alleging that adequate investigation at that point would have identified the developing subarachnoid hemorrhage. The court dismissed the action on both standard of care and causation grounds.
The case is doctrinally important for several reasons. It is a recent articulation of the standard of care for emergency department evaluation of headache, including the central role of the “thunderclap” headache framework. It illustrates the practical application of the differential diagnostic framework where the clinical picture is consistent with a common diagnosis and the warning features for the rare but serious diagnosis are absent. It is one of the cleanest recent examples of a counterfactual causation defeat in a delayed-diagnosis case: the court found that even if the alleged investigation had been performed, the result would not have changed because the underlying pathology had not yet developed in a form that the investigation would have detected. And it includes a useful illustration of the court’s approach to damages assessment in cases where the primary defence prevails but the court provides an alternative finding on damages.
The clinical context — headache, SAH, and emergency department workup
A brief clinical overview is useful for the analysis.
Subarachnoid hemorrhage. Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space, the area between the arachnoid membrane and the pia mater that covers the brain. The most common cause of non-traumatic SAH is the rupture of a cerebral aneurysm, although SAH can also be caused by arteriovenous malformations, perimesencephalic hemorrhage of unclear origin, and other vascular abnormalities. SAH is a life-threatening condition: untreated SAH has high mortality rates from the initial bleed and from subsequent re-rupture, vasospasm, hydrocephalus, and other complications. Modern treatment includes securing the bleeding source (typically by endovascular coiling or surgical clipping) and managing the secondary complications. Early diagnosis is critical because the trajectory of outcomes is closely tied to the time between rupture and treatment.
The thunderclap headache. The thunderclap headache is the classic clinical presentation of SAH. It is described as a sudden onset severe headache, reaching peak intensity within seconds or at most a few minutes. Patients often describe it as “the worst headache of my life” or “like being hit on the head with a baseball bat.” The thunderclap pattern is highly suggestive of SAH and warrants urgent investigation regardless of other clinical features. Modern emergency medicine teaching emphasizes the thunderclap pattern as the principal clinical signal for SAH, and the practical reality is that an emergency physician confronted with a thunderclap headache will order CT and (where CT is negative) lumbar puncture to rule out SAH as part of the workup.
The gradual onset headache. A gradual onset headache, by contrast, has a much broader differential. Tension headache, migraine, sinus pressure, viral illness, and similar benign causes typically present with a gradual onset over minutes to hours rather than the sudden peak intensity of the thunderclap pattern. SAH can rarely present with a gradual headache, but the modal presentation is the thunderclap. The gradual-onset presentation is therefore not a clinical signal for SAH in the same way the thunderclap is.
The severity scale. Patients with SAH typically rate their headache severity at the highest end of the scale (10 out of 10 or “worse than 10”). The severity is part of the pattern recognition. A patient who rates their headache at 7 out of 10 has reported a “moderate” headache by most clinical conventions. The combination of severity rating and onset pattern informs the differential.
Other warning signs for SAH. Beyond the thunderclap onset and severity, other warning signs include:
- Neck stiffness or photophobia (meningismus from blood irritating the meninges)
- Brief loss of consciousness or syncope at the time of the headache onset
- Focal neurological symptoms (vision changes, weakness, speech disturbance)
- Vomiting accompanying the headache
- Seizure
- Sentinel bleed history (a previous severe headache that resolved on its own, sometimes called a warning leak)
The absence of these warning signs, combined with a gradual onset and a moderate severity rating, weighs against SAH on the differential.
The role of CT. Modern CT scanners can detect the majority of acute SAH within the first 24 to 48 hours after the bleed. The sensitivity is highest in the first 6 hours and declines over time as the blood is metabolized. A negative CT performed during the appropriate time window has substantial reassurance value. A negative CT performed outside the time window has less reassurance value, and additional investigation (lumbar puncture for xanthochromia, CT angiography, or MRI) may be considered if the clinical suspicion remains.
The role of lumbar puncture. Lumbar puncture (LP) involves insertion of a needle into the lumbar subarachnoid space to obtain a sample of cerebrospinal fluid. In the context of SAH workup, LP is used to detect blood breakdown products (xanthochromia) that indicate prior bleeding. The investigation is typically reserved for patients with high clinical suspicion of SAH and a negative CT scan. LP is invasive, has its own risks (post-LP headache, infection, rare neurological complications), and is not performed routinely.
The role of the recent prior negative CT. Where a patient has had a recent negative CT for the same complaint, the clinical decision-making for a subsequent presentation is informed by that earlier investigation. A patient with a documented negative CT performed within an appropriate time window has had a meaningful component of the SAH workup completed. The framework does not require the CT to be repeated unless the clinical picture has materially changed or the time window has elapsed.
The Ottawa SAH Rule. Modern emergency medicine practice increasingly applies the Ottawa SAH Rule, a clinical decision tool developed at the University of Ottawa for risk stratification of headache patients. The rule identifies criteria that warrant SAH investigation: age 40 or older, neck pain or stiffness, witnessed loss of consciousness, onset during exertion, thunderclap headache (instantly peaking pain), or limited neck flexion on examination. Patients meeting one or more of these criteria warrant investigation. The framework does not displace clinical judgment but provides a structured approach to risk stratification.
The facts
The patient. The plaintiff was a 54-year-old man. He attended two different emergency departments three times in the first week of August 2018 with headache complaints.
The first visit. On August 1, 2018, the plaintiff presented to the first emergency department. He was assessed by two emergency physicians. A CT scan of the head was performed and was negative. He was treated for his headache, the headache reportedly improved with medication, and he was discharged.
The second visit. On August 4, 2018, three days after the first visit, the plaintiff presented to a second emergency department with similar headache complaints. He was assessed by Dr. Neil Long, an emergency medicine physician. Dr. Long took a focused history including specifically confirming with the plaintiff that the headache had developed gradually rather than suddenly. The distinction between gradual and sudden onset is doctrinally important: a gradual onset is consistent with the broad differential of benign headache causes, while a sudden onset (thunderclap) is the classical clinical signal for SAH.
Dr. Long diagnosed migraine and provided treatment. The plaintiff’s symptoms improved after the treatment. He was discharged with advice to return if the headache recurred or worsened. The plaintiff rated his headache severity at 7 out of 10 during the August 1 and August 4 presentations.
The third visit. On August 8, 2018, four days after the August 4 visit and seven days after the initial presentation, the plaintiff returned to the same emergency department. The clinical picture had changed: this time, a CT scan revealed a subarachnoid hemorrhage requiring neurosurgical intervention. The plaintiff was hospitalized until August 23.
The action. The plaintiff brought a civil action against Dr. Long alleging that adequate investigation on August 4 (specifically a CT scan and, if negative, a lumbar puncture) would have identified the developing SAH. The plaintiff’s theory was that the August 4 headache was already a manifestation of the developing aneurysmal pathology, and that earlier diagnosis would have permitted earlier intervention and better outcome.
The expert evidence
Both sides called expert evidence on the standard of care and on causation.
The plaintiff’s expert. An expert in emergency medicine testified for the plaintiff. The expert’s opinion proceeded from the premise that the plaintiff had experienced a thunderclap headache at the August 4 presentation. On that premise, the expert concluded that the standard of care required CT and (if necessary) lumbar puncture to rule out SAH, and that Dr. Long’s failure to order these investigations fell below the standard. The expert emphasized that patients presenting with thunderclap headaches are almost always correctly diagnosed when the appropriate investigation pathway is followed.
The defence experts. Three experts testified for the defence on different aspects of the case.
On the standard of care for Dr. Long’s specific assessment. An expert in emergency medicine concluded that Dr. Long’s assessment and treatment were appropriate and not unusual for any adult patient presenting with an acute headache in the emergency department. The expert noted that Dr. Long thoroughly documented the gradual onset of the headache, followed a standard treatment plan, observed improvement after medication, and provided proper discharge instructions to return if symptoms continued. Given the recent negative CT from three days earlier, managing the symptoms and discharging the plaintiff was reasonable.
On the standard of care framework more broadly. A second emergency medicine expert addressed the framework for headache investigation. The expert noted that not all headache patients require CT or lumbar puncture, and that even the plaintiff’s own expert limited these investigations to cases with a thunderclap headache. The expert noted that the plaintiff did not have a thunderclap headache during the August 1 or August 4 visits and that the typical warning signs of SAH (neck stiffness, loss of consciousness, focal neurological signs) were absent. Given the available information, the decision not to perform a lumbar puncture was reasonable.
On the severity of the headaches and the statistical differential. A neurologist addressed the severity of the headaches. The plaintiff had rated his headache at 7 out of 10 on August 1 and August 4. The expert noted that SAH patients typically rate their headache at 10 or 11 out of 10, well above the moderate range. The 7 out of 10 rating was characterized as inconsistent with the intense pain usually associated with SAH. While the expert acknowledged that a first migraine after age 50 is uncommon, the expert testified that on the available clinical picture it was statistically much more likely that the plaintiff was experiencing a migraine rather than an SAH.
The structure of expert disagreement. The expert disagreement was not primarily about the underlying medical principles. Both sides accepted the framework that a thunderclap headache is the principal clinical signal for SAH and that CT and (where indicated) LP are the appropriate investigations when the framework supports that pathway. The disagreement was about whether the plaintiff had experienced a thunderclap headache on August 4 and, relatedly, whether the clinical picture warranted the more extensive investigation pathway.
The court’s analysis
The court found in favour of the defendant. The reasoning proceeded along two principal axes: standard of care and causation.
The standard of care analysis. The court accepted Dr. Long’s evidence that he had specifically taken steps to determine whether the plaintiff’s headache had a sudden onset. The medical records did not describe a sudden onset headache. The plaintiff’s own description, as documented at the time, was of a gradual onset. The court was satisfied that Dr. Long had taken adequate steps to assess whether the headache was sudden onset (the determination being important to the possible diagnosis of SAH) and that he had reasonably concluded it was not. The court could not conclude that Dr. Long had failed to meet the standard of care by any failure to take this step.
The standard of care analysis is significant because it engages two distinct frameworks. First, it engages the “documented history-taking” framework: Dr. Long’s contemporaneous documentation of his inquiry into onset pattern supported the standard of care finding. Second, it engages the “expert opinion built on rejected factual premise” framework: the plaintiff’s expert had premised the opinion on the existence of a thunderclap headache, but the court rejected that factual premise. With the premise rejected, the expert opinion built on it could not support the standard of care finding the plaintiff sought.
The causation analysis. The court found that even if Dr. Long had breached the standard of care by failing to order CT and lumbar puncture on August 4, the breach would not have caused the plaintiff’s injuries. The reasoning was that:
- The August 4 headache was most likely a migraine, not the manifestation of a developing SAH
- A CT scan on August 4, if performed, would not have detected a bleed because the bleed had not yet occurred (or had not occurred in a form detectable by CT)
- A lumbar puncture on August 4, if performed, would not have detected xanthochromia for the same reason
- Without a positive investigation, no surgical intervention would have been planned
- The eventual SAH on or around August 8 would have followed the same trajectory regardless of the investigations on August 4
The causation analysis is one of the cleanest recent examples of the counterfactual reasoning framework in delayed-diagnosis litigation. The framework asks what would have happened on the balance of probabilities had the alleged breach not occurred. Where the answer is “the same outcome would have followed,” causation is not established regardless of whether the standard of care was met or not.
The alternative damages finding. The court provided an alternative finding on damages even though it dismissed the action. The framework reflects the common judicial practice of addressing all the issues that have been litigated, so that an appellate court can address damages without remitting if the appellate court were to reverse on liability. The court considered $50,000 to be fair compensation for the plaintiff’s pain and suffering attributable to the alleged delay. The court then reduced this figure by half to $25,000 to reflect that a portion of the harm would have occurred regardless of any alleged negligence. The framework is the apportionment of damages where part of the injury is attributable to the original condition and part to the alleged delay or negligent care.
The doctrinal anchors
Several doctrinal anchors emerge from the case.
The “thunderclap headache” framework. The thunderclap headache is the principal clinical signal for SAH in modern emergency medicine practice. The framework requires careful inquiry into the onset pattern as a routine element of headache assessment. Where the thunderclap pattern is present, the framework supports CT and (where indicated) lumbar puncture as part of the workup. Where the pattern is absent, the framework supports a broader differential consistent with the patient’s specific clinical picture.
The “gradual onset” history-taking framework. Active inquiry by the physician into the onset pattern of a headache is a recognized element of the standard of care. The framework recognizes that patients may not spontaneously volunteer the timing details, and that the physician’s structured questioning is what surfaces the relevant clinical information. The contemporaneous documentation of the inquiry and the patient’s response supports the standard of care analysis.
The “recent prior negative CT as reassurance” framework. Where a patient has had a recent negative CT for the same complaint and presents again within an appropriate time window without material change in the clinical picture, the recent negative CT is relevant to the subsequent decision-making. The framework does not categorically displace the need for additional investigation, but it informs the analysis of whether further investigation is required.
The “severity rating scale” framework. Patient-reported severity ratings on the standard 10-point scale provide one data point in the headache differential. SAH patients typically rate their headache at the high end of the scale (10 out of 10 or “worse than 10”). A patient who rates their headache at 7 out of 10 has reported a moderate headache, which is less consistent with the typical SAH presentation. The framework uses the severity rating in combination with other clinical features rather than as a standalone determinant.
The “statistical likelihood / base rate” framework. The differential diagnosis for headache includes both common diagnoses (migraine, tension headache, viral illness) and rare diagnoses (SAH, meningitis, mass lesion). The framework requires the physician to consider the base rate of each diagnosis along with the specific clinical features. A clinical picture consistent with a common diagnosis and without warning features for a rare diagnosis supports the common diagnosis on the differential.
The “warning signs absent” framework. The absence of the typical warning signs for SAH (neck stiffness, loss of consciousness, focal neurological signs, vomiting, seizure) weighs against SAH on the differential. The framework recognizes that a positive finding of these warning signs would increase suspicion for SAH; their absence reduces suspicion.
The “expert opinion built on rejected factual premise” framework. Where an expert opinion proceeds from a factual premise that the court rejects, the expert opinion built on the rejected premise loses its evidentiary weight. The framework is generalizable across medical malpractice cases. The implication for case evaluation is that the factual premises of expert opinions need to be carefully assessed for whether they will hold up at trial.
The “counterfactual causation in delayed-diagnosis” framework. Where the alleged breach is a failure to investigate at an earlier time, the causation analysis asks what the investigation would have shown had it been performed. Where the underlying pathology had not yet developed in a form detectable by the proposed investigation, the investigation would not have changed the trajectory. The framework defeats the case at the causation stage regardless of whether the standard of care was met.
The “documented history-taking” framework. Contemporaneous documentation of the physician’s inquiry into the patient’s clinical features is the primary evidence of the physician’s reasoning. Where the documentation is detailed and consistent with the clinical record, the framework supports the standard of care finding. Where the documentation is sparse or inconsistent, the framework supports a more critical analysis.
The “ED headache differential” framework. Emergency department evaluation of headache requires a structured approach to the differential including the relevant warning features and the role of imaging and lumbar puncture. The framework operates as a working clinical algorithm rather than a categorical rule.
The “alternative damages finding” pattern. Trial courts often provide alternative findings on damages even where they have dismissed the liability claim, to facilitate appellate review without remand. The framework is a procedural feature that becomes substantive when the alternative finding becomes the basis for an appellate reversal. The framework also includes the principle of apportionment where part of the harm is attributable to the underlying condition rather than to the alleged breach.
The “defendant-favourable trial outcome in ED missed diagnosis” pattern. Several recent trial-level outcomes have favoured defendants in cases involving alleged ED missed diagnoses (appendicitis, stroke, aortic dissection, aneurysm, and now SAH). The pattern is consistent with the framework that the standard of care does not require perfect diagnostic accuracy in every presentation, particularly where the clinical picture is consistent with a common diagnosis and the warning features for the rare diagnosis are absent.
Why this case matters
For prospective plaintiffs and families. The case is a useful illustration of the structure of delayed-diagnosis claims in ED missed diagnosis cases.
Some practical observations:
The clinical features documented at the time matter. Where the physician’s contemporaneous documentation describes a clinical picture that is consistent with a benign diagnosis, the case becomes much harder to advance. Where the documentation describes the warning features for the more serious diagnosis (sudden onset, severe severity rating, accompanying symptoms), the case has a more sustainable foundation. The contemporaneous record is the principal evidence of what the physician was confronted with at the time.
Expert opinion needs a factual foundation. Expert opinion built on a factual premise that the court rejects does not support the case. The factual foundation must be sustainable on the contemporaneous record. Where the plaintiff’s account of the clinical features differs from the contemporaneous record, the court is typically required to resolve the factual question, and the expert opinion built on the disputed premise depends on that resolution.
Counterfactual causation is a major hurdle in delay cases. The framework asks what would have happened on the balance of probabilities had the investigation been performed at the earlier time. Where the underlying pathology had not yet developed in a form detectable by the investigation, the case fails on causation regardless of standard of care. The framework is one of the most consequential defendant-favourable doctrines in delayed-diagnosis litigation.
The recognized profile of the dangerous diagnosis matters. Where the dangerous diagnosis (SAH, here) has a recognized clinical profile (thunderclap onset, severity at the top of the scale, accompanying warning features) and the patient’s actual presentation does not match that profile, the case becomes harder. The framework does not require the dangerous diagnosis to always manifest with the classic profile, but it does require the plaintiff to explain why the case warrants the more extensive investigation pathway despite the absence of the typical signals.
For more on the general framework for evaluating delayed-diagnosis cases, see Why Many Medical Malpractice Cases Are Declined in Ontario and Suing for Medical Malpractice in Ontario: What You Need to Know.
For clinicians and emergency department teams. A few practical observations:
Document the inquiry into onset. Where a headache patient is being evaluated, the physician’s structured inquiry into the onset pattern is part of the standard of care. The contemporaneous documentation of the inquiry and the patient’s response provides the primary evidence of the workup at trial. Detailed and specific documentation supports the analysis.
Document the warning signs analysis. Where the warning signs for the dangerous diagnoses are absent, the documentation should reflect that the physician considered them. The framework treats the absent-but-considered warning signs as part of the reasoned differential.
The Ottawa SAH Rule is a useful structured approach. Where the framework supports it, the Ottawa SAH Rule or similar structured tools can support the reasoned differential analysis. The framework does not replace clinical judgment but provides a documented basis for the approach.
Recent prior CT is relevant but not categorical. Where a recent CT has been negative, the framework supports its consideration in the subsequent decision-making, but does not categorically displace the need for further investigation if the clinical picture has materially changed.
Decision Date: July 21, 2025
Jurisdiction: Supreme Court of British Columbia
Citation: Ricottone v Long, 2025 BCSC 1388 (CanLII)
Outcome: Judgment in favour of the defendant emergency medicine physician. The court found that the defendant had not breached the standard of care on his August 4, 2018 assessment of the plaintiff, who had presented with a headache that the contemporaneous documentation described as gradual in onset and moderate in severity (7 out of 10). The defendant had specifically inquired into whether the headache was sudden onset (the principal clinical signal for subarachnoid hemorrhage) and had reasonably concluded that it was not. The court further found that even if a breach of the standard of care had been established, causation would not have been established: the August 4 headache was most likely a migraine rather than the manifestation of a developing SAH, and a CT scan or lumbar puncture on August 4 would not have detected a bleed that had not yet occurred. The court provided an alternative finding on damages of $50,000 for pain and suffering reduced by half to $25,000 to reflect the portion of the harm that would have occurred regardless of any alleged negligence.
Key authorities: Wilson v Swanson, [1956] SCR 804 (specialist standard); Crits v Sylvester, [1956] OR 132 (medical practitioner standard); ter Neuzen v Korn, [1995] 3 SCR 674 (specialist standard); Snell v Farrell, [1990] 2 SCR 311 (robust and pragmatic causation); Clements v Clements, 2012 SCC 32 (but-for causation framework); Athey v Leonati, [1996] 3 SCR 458 (multiple causes / apportionment); the Ottawa SAH Rule (clinical decision tool for risk stratification of headache patients).
Ricottone v Long: Thunderclap Headache, SAH Differential, and Counterfactual Causation
BC court dismisses ED malpractice claim involving missed subarachnoid hemorrhage where patient lacked thunderclap headache and the bleed had not yet occurred.
Headache is one of the most common presenting complaints in Canadian emergency departments. The vast majority of headache presentations have benign or self-limited causes (tension headache, migraine, viral illness, dehydration). A small but important proportion are caused by serious conditions that require urgent diagnosis and intervention (subarachnoid hemorrhage, meningitis, cerebral venous sinus thrombosis, stroke, mass lesions). The framework for distinguishing between the benign and the dangerous causes is one of the most carefully developed areas of emergency medicine. The standard of care turns on careful history-taking, focused examination, and judicious use of investigations. Where the clinical picture is consistent with a benign cause and the warning features for dangerous causes are absent, the framework supports symptomatic management and discharge with return precautions. Where the warning features are present, the framework supports immediate investigation including computed tomography of the head and, in selected cases, lumbar puncture.
Ricottone v Long, 2025 BCSC 1388, released by the Supreme Court of British Columbia on July 21, 2025, is a recent application of the framework. The plaintiff was a 54-year-old man who presented to two different emergency departments in early August 2018 with headache complaints. A CT scan performed during the first visit was negative. At his second presentation three days later, the emergency physician diagnosed a migraine and discharged him with return precautions. Four days after that, the plaintiff returned to the same emergency department with new symptoms, and a subarachnoid hemorrhage was diagnosed. The plaintiff brought an action against the emergency physician from the second visit, alleging that adequate investigation at that point would have identified the developing subarachnoid hemorrhage. The court dismissed the action on both standard of care and causation grounds.
The case is doctrinally important for several reasons. It is a recent articulation of the standard of care for emergency department evaluation of headache, including the central role of the “thunderclap” headache framework. It illustrates the practical application of the differential diagnostic framework where the clinical picture is consistent with a common diagnosis and the warning features for the rare but serious diagnosis are absent. It is one of the cleanest recent examples of a counterfactual causation defeat in a delayed-diagnosis case: the court found that even if the alleged investigation had been performed, the result would not have changed because the underlying pathology had not yet developed in a form that the investigation would have detected. And it includes a useful illustration of the court’s approach to damages assessment in cases where the primary defence prevails but the court provides an alternative finding on damages.
The clinical context — headache, SAH, and emergency department workup
A brief clinical overview is useful for the analysis.
Subarachnoid hemorrhage. Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space, the area between the arachnoid membrane and the pia mater that covers the brain. The most common cause of non-traumatic SAH is the rupture of a cerebral aneurysm, although SAH can also be caused by arteriovenous malformations, perimesencephalic hemorrhage of unclear origin, and other vascular abnormalities. SAH is a life-threatening condition: untreated SAH has high mortality rates from the initial bleed and from subsequent re-rupture, vasospasm, hydrocephalus, and other complications. Modern treatment includes securing the bleeding source (typically by endovascular coiling or surgical clipping) and managing the secondary complications. Early diagnosis is critical because the trajectory of outcomes is closely tied to the time between rupture and treatment.
The thunderclap headache. The thunderclap headache is the classic clinical presentation of SAH. It is described as a sudden onset severe headache, reaching peak intensity within seconds or at most a few minutes. Patients often describe it as “the worst headache of my life” or “like being hit on the head with a baseball bat.” The thunderclap pattern is highly suggestive of SAH and warrants urgent investigation regardless of other clinical features. Modern emergency medicine teaching emphasizes the thunderclap pattern as the principal clinical signal for SAH, and the practical reality is that an emergency physician confronted with a thunderclap headache will order CT and (where CT is negative) lumbar puncture to rule out SAH as part of the workup.
The gradual onset headache. A gradual onset headache, by contrast, has a much broader differential. Tension headache, migraine, sinus pressure, viral illness, and similar benign causes typically present with a gradual onset over minutes to hours rather than the sudden peak intensity of the thunderclap pattern. SAH can rarely present with a gradual headache, but the modal presentation is the thunderclap. The gradual-onset presentation is therefore not a clinical signal for SAH in the same way the thunderclap is.
The severity scale. Patients with SAH typically rate their headache severity at the highest end of the scale (10 out of 10 or “worse than 10”). The severity is part of the pattern recognition. A patient who rates their headache at 7 out of 10 has reported a “moderate” headache by most clinical conventions. The combination of severity rating and onset pattern informs the differential.
Other warning signs for SAH. Beyond the thunderclap onset and severity, other warning signs include:
The absence of these warning signs, combined with a gradual onset and a moderate severity rating, weighs against SAH on the differential.
The role of CT. Modern CT scanners can detect the majority of acute SAH within the first 24 to 48 hours after the bleed. The sensitivity is highest in the first 6 hours and declines over time as the blood is metabolized. A negative CT performed during the appropriate time window has substantial reassurance value. A negative CT performed outside the time window has less reassurance value, and additional investigation (lumbar puncture for xanthochromia, CT angiography, or MRI) may be considered if the clinical suspicion remains.
The role of lumbar puncture. Lumbar puncture (LP) involves insertion of a needle into the lumbar subarachnoid space to obtain a sample of cerebrospinal fluid. In the context of SAH workup, LP is used to detect blood breakdown products (xanthochromia) that indicate prior bleeding. The investigation is typically reserved for patients with high clinical suspicion of SAH and a negative CT scan. LP is invasive, has its own risks (post-LP headache, infection, rare neurological complications), and is not performed routinely.
The role of the recent prior negative CT. Where a patient has had a recent negative CT for the same complaint, the clinical decision-making for a subsequent presentation is informed by that earlier investigation. A patient with a documented negative CT performed within an appropriate time window has had a meaningful component of the SAH workup completed. The framework does not require the CT to be repeated unless the clinical picture has materially changed or the time window has elapsed.
The Ottawa SAH Rule. Modern emergency medicine practice increasingly applies the Ottawa SAH Rule, a clinical decision tool developed at the University of Ottawa for risk stratification of headache patients. The rule identifies criteria that warrant SAH investigation: age 40 or older, neck pain or stiffness, witnessed loss of consciousness, onset during exertion, thunderclap headache (instantly peaking pain), or limited neck flexion on examination. Patients meeting one or more of these criteria warrant investigation. The framework does not displace clinical judgment but provides a structured approach to risk stratification.
The facts
The patient. The plaintiff was a 54-year-old man. He attended two different emergency departments three times in the first week of August 2018 with headache complaints.
The first visit. On August 1, 2018, the plaintiff presented to the first emergency department. He was assessed by two emergency physicians. A CT scan of the head was performed and was negative. He was treated for his headache, the headache reportedly improved with medication, and he was discharged.
The second visit. On August 4, 2018, three days after the first visit, the plaintiff presented to a second emergency department with similar headache complaints. He was assessed by Dr. Neil Long, an emergency medicine physician. Dr. Long took a focused history including specifically confirming with the plaintiff that the headache had developed gradually rather than suddenly. The distinction between gradual and sudden onset is doctrinally important: a gradual onset is consistent with the broad differential of benign headache causes, while a sudden onset (thunderclap) is the classical clinical signal for SAH.
Dr. Long diagnosed migraine and provided treatment. The plaintiff’s symptoms improved after the treatment. He was discharged with advice to return if the headache recurred or worsened. The plaintiff rated his headache severity at 7 out of 10 during the August 1 and August 4 presentations.
The third visit. On August 8, 2018, four days after the August 4 visit and seven days after the initial presentation, the plaintiff returned to the same emergency department. The clinical picture had changed: this time, a CT scan revealed a subarachnoid hemorrhage requiring neurosurgical intervention. The plaintiff was hospitalized until August 23.
The action. The plaintiff brought a civil action against Dr. Long alleging that adequate investigation on August 4 (specifically a CT scan and, if negative, a lumbar puncture) would have identified the developing SAH. The plaintiff’s theory was that the August 4 headache was already a manifestation of the developing aneurysmal pathology, and that earlier diagnosis would have permitted earlier intervention and better outcome.
The expert evidence
Both sides called expert evidence on the standard of care and on causation.
The plaintiff’s expert. An expert in emergency medicine testified for the plaintiff. The expert’s opinion proceeded from the premise that the plaintiff had experienced a thunderclap headache at the August 4 presentation. On that premise, the expert concluded that the standard of care required CT and (if necessary) lumbar puncture to rule out SAH, and that Dr. Long’s failure to order these investigations fell below the standard. The expert emphasized that patients presenting with thunderclap headaches are almost always correctly diagnosed when the appropriate investigation pathway is followed.
The defence experts. Three experts testified for the defence on different aspects of the case.
On the standard of care for Dr. Long’s specific assessment. An expert in emergency medicine concluded that Dr. Long’s assessment and treatment were appropriate and not unusual for any adult patient presenting with an acute headache in the emergency department. The expert noted that Dr. Long thoroughly documented the gradual onset of the headache, followed a standard treatment plan, observed improvement after medication, and provided proper discharge instructions to return if symptoms continued. Given the recent negative CT from three days earlier, managing the symptoms and discharging the plaintiff was reasonable.
On the standard of care framework more broadly. A second emergency medicine expert addressed the framework for headache investigation. The expert noted that not all headache patients require CT or lumbar puncture, and that even the plaintiff’s own expert limited these investigations to cases with a thunderclap headache. The expert noted that the plaintiff did not have a thunderclap headache during the August 1 or August 4 visits and that the typical warning signs of SAH (neck stiffness, loss of consciousness, focal neurological signs) were absent. Given the available information, the decision not to perform a lumbar puncture was reasonable.
On the severity of the headaches and the statistical differential. A neurologist addressed the severity of the headaches. The plaintiff had rated his headache at 7 out of 10 on August 1 and August 4. The expert noted that SAH patients typically rate their headache at 10 or 11 out of 10, well above the moderate range. The 7 out of 10 rating was characterized as inconsistent with the intense pain usually associated with SAH. While the expert acknowledged that a first migraine after age 50 is uncommon, the expert testified that on the available clinical picture it was statistically much more likely that the plaintiff was experiencing a migraine rather than an SAH.
The structure of expert disagreement. The expert disagreement was not primarily about the underlying medical principles. Both sides accepted the framework that a thunderclap headache is the principal clinical signal for SAH and that CT and (where indicated) LP are the appropriate investigations when the framework supports that pathway. The disagreement was about whether the plaintiff had experienced a thunderclap headache on August 4 and, relatedly, whether the clinical picture warranted the more extensive investigation pathway.
The court’s analysis
The court found in favour of the defendant. The reasoning proceeded along two principal axes: standard of care and causation.
The standard of care analysis. The court accepted Dr. Long’s evidence that he had specifically taken steps to determine whether the plaintiff’s headache had a sudden onset. The medical records did not describe a sudden onset headache. The plaintiff’s own description, as documented at the time, was of a gradual onset. The court was satisfied that Dr. Long had taken adequate steps to assess whether the headache was sudden onset (the determination being important to the possible diagnosis of SAH) and that he had reasonably concluded it was not. The court could not conclude that Dr. Long had failed to meet the standard of care by any failure to take this step.
The standard of care analysis is significant because it engages two distinct frameworks. First, it engages the “documented history-taking” framework: Dr. Long’s contemporaneous documentation of his inquiry into onset pattern supported the standard of care finding. Second, it engages the “expert opinion built on rejected factual premise” framework: the plaintiff’s expert had premised the opinion on the existence of a thunderclap headache, but the court rejected that factual premise. With the premise rejected, the expert opinion built on it could not support the standard of care finding the plaintiff sought.
The causation analysis. The court found that even if Dr. Long had breached the standard of care by failing to order CT and lumbar puncture on August 4, the breach would not have caused the plaintiff’s injuries. The reasoning was that:
The causation analysis is one of the cleanest recent examples of the counterfactual reasoning framework in delayed-diagnosis litigation. The framework asks what would have happened on the balance of probabilities had the alleged breach not occurred. Where the answer is “the same outcome would have followed,” causation is not established regardless of whether the standard of care was met or not.
The alternative damages finding. The court provided an alternative finding on damages even though it dismissed the action. The framework reflects the common judicial practice of addressing all the issues that have been litigated, so that an appellate court can address damages without remitting if the appellate court were to reverse on liability. The court considered $50,000 to be fair compensation for the plaintiff’s pain and suffering attributable to the alleged delay. The court then reduced this figure by half to $25,000 to reflect that a portion of the harm would have occurred regardless of any alleged negligence. The framework is the apportionment of damages where part of the injury is attributable to the original condition and part to the alleged delay or negligent care.
The doctrinal anchors
Several doctrinal anchors emerge from the case.
The “thunderclap headache” framework. The thunderclap headache is the principal clinical signal for SAH in modern emergency medicine practice. The framework requires careful inquiry into the onset pattern as a routine element of headache assessment. Where the thunderclap pattern is present, the framework supports CT and (where indicated) lumbar puncture as part of the workup. Where the pattern is absent, the framework supports a broader differential consistent with the patient’s specific clinical picture.
The “gradual onset” history-taking framework. Active inquiry by the physician into the onset pattern of a headache is a recognized element of the standard of care. The framework recognizes that patients may not spontaneously volunteer the timing details, and that the physician’s structured questioning is what surfaces the relevant clinical information. The contemporaneous documentation of the inquiry and the patient’s response supports the standard of care analysis.
The “recent prior negative CT as reassurance” framework. Where a patient has had a recent negative CT for the same complaint and presents again within an appropriate time window without material change in the clinical picture, the recent negative CT is relevant to the subsequent decision-making. The framework does not categorically displace the need for additional investigation, but it informs the analysis of whether further investigation is required.
The “severity rating scale” framework. Patient-reported severity ratings on the standard 10-point scale provide one data point in the headache differential. SAH patients typically rate their headache at the high end of the scale (10 out of 10 or “worse than 10”). A patient who rates their headache at 7 out of 10 has reported a moderate headache, which is less consistent with the typical SAH presentation. The framework uses the severity rating in combination with other clinical features rather than as a standalone determinant.
The “statistical likelihood / base rate” framework. The differential diagnosis for headache includes both common diagnoses (migraine, tension headache, viral illness) and rare diagnoses (SAH, meningitis, mass lesion). The framework requires the physician to consider the base rate of each diagnosis along with the specific clinical features. A clinical picture consistent with a common diagnosis and without warning features for a rare diagnosis supports the common diagnosis on the differential.
The “warning signs absent” framework. The absence of the typical warning signs for SAH (neck stiffness, loss of consciousness, focal neurological signs, vomiting, seizure) weighs against SAH on the differential. The framework recognizes that a positive finding of these warning signs would increase suspicion for SAH; their absence reduces suspicion.
The “expert opinion built on rejected factual premise” framework. Where an expert opinion proceeds from a factual premise that the court rejects, the expert opinion built on the rejected premise loses its evidentiary weight. The framework is generalizable across medical malpractice cases. The implication for case evaluation is that the factual premises of expert opinions need to be carefully assessed for whether they will hold up at trial.
The “counterfactual causation in delayed-diagnosis” framework. Where the alleged breach is a failure to investigate at an earlier time, the causation analysis asks what the investigation would have shown had it been performed. Where the underlying pathology had not yet developed in a form detectable by the proposed investigation, the investigation would not have changed the trajectory. The framework defeats the case at the causation stage regardless of whether the standard of care was met.
The “documented history-taking” framework. Contemporaneous documentation of the physician’s inquiry into the patient’s clinical features is the primary evidence of the physician’s reasoning. Where the documentation is detailed and consistent with the clinical record, the framework supports the standard of care finding. Where the documentation is sparse or inconsistent, the framework supports a more critical analysis.
The “ED headache differential” framework. Emergency department evaluation of headache requires a structured approach to the differential including the relevant warning features and the role of imaging and lumbar puncture. The framework operates as a working clinical algorithm rather than a categorical rule.
The “alternative damages finding” pattern. Trial courts often provide alternative findings on damages even where they have dismissed the liability claim, to facilitate appellate review without remand. The framework is a procedural feature that becomes substantive when the alternative finding becomes the basis for an appellate reversal. The framework also includes the principle of apportionment where part of the harm is attributable to the underlying condition rather than to the alleged breach.
The “defendant-favourable trial outcome in ED missed diagnosis” pattern. Several recent trial-level outcomes have favoured defendants in cases involving alleged ED missed diagnoses (appendicitis, stroke, aortic dissection, aneurysm, and now SAH). The pattern is consistent with the framework that the standard of care does not require perfect diagnostic accuracy in every presentation, particularly where the clinical picture is consistent with a common diagnosis and the warning features for the rare diagnosis are absent.
Why this case matters
For prospective plaintiffs and families. The case is a useful illustration of the structure of delayed-diagnosis claims in ED missed diagnosis cases.
Some practical observations:
The clinical features documented at the time matter. Where the physician’s contemporaneous documentation describes a clinical picture that is consistent with a benign diagnosis, the case becomes much harder to advance. Where the documentation describes the warning features for the more serious diagnosis (sudden onset, severe severity rating, accompanying symptoms), the case has a more sustainable foundation. The contemporaneous record is the principal evidence of what the physician was confronted with at the time.
Expert opinion needs a factual foundation. Expert opinion built on a factual premise that the court rejects does not support the case. The factual foundation must be sustainable on the contemporaneous record. Where the plaintiff’s account of the clinical features differs from the contemporaneous record, the court is typically required to resolve the factual question, and the expert opinion built on the disputed premise depends on that resolution.
Counterfactual causation is a major hurdle in delay cases. The framework asks what would have happened on the balance of probabilities had the investigation been performed at the earlier time. Where the underlying pathology had not yet developed in a form detectable by the investigation, the case fails on causation regardless of standard of care. The framework is one of the most consequential defendant-favourable doctrines in delayed-diagnosis litigation.
The recognized profile of the dangerous diagnosis matters. Where the dangerous diagnosis (SAH, here) has a recognized clinical profile (thunderclap onset, severity at the top of the scale, accompanying warning features) and the patient’s actual presentation does not match that profile, the case becomes harder. The framework does not require the dangerous diagnosis to always manifest with the classic profile, but it does require the plaintiff to explain why the case warrants the more extensive investigation pathway despite the absence of the typical signals.
For more on the general framework for evaluating delayed-diagnosis cases, see Why Many Medical Malpractice Cases Are Declined in Ontario and Suing for Medical Malpractice in Ontario: What You Need to Know.
For clinicians and emergency department teams. A few practical observations:
Document the inquiry into onset. Where a headache patient is being evaluated, the physician’s structured inquiry into the onset pattern is part of the standard of care. The contemporaneous documentation of the inquiry and the patient’s response provides the primary evidence of the workup at trial. Detailed and specific documentation supports the analysis.
Document the warning signs analysis. Where the warning signs for the dangerous diagnoses are absent, the documentation should reflect that the physician considered them. The framework treats the absent-but-considered warning signs as part of the reasoned differential.
The Ottawa SAH Rule is a useful structured approach. Where the framework supports it, the Ottawa SAH Rule or similar structured tools can support the reasoned differential analysis. The framework does not replace clinical judgment but provides a documented basis for the approach.
Recent prior CT is relevant but not categorical. Where a recent CT has been negative, the framework supports its consideration in the subsequent decision-making, but does not categorically displace the need for further investigation if the clinical picture has materially changed.
Decision Date: July 21, 2025
Jurisdiction: Supreme Court of British Columbia
Citation: Ricottone v Long, 2025 BCSC 1388 (CanLII)
Outcome: Judgment in favour of the defendant emergency medicine physician. The court found that the defendant had not breached the standard of care on his August 4, 2018 assessment of the plaintiff, who had presented with a headache that the contemporaneous documentation described as gradual in onset and moderate in severity (7 out of 10). The defendant had specifically inquired into whether the headache was sudden onset (the principal clinical signal for subarachnoid hemorrhage) and had reasonably concluded that it was not. The court further found that even if a breach of the standard of care had been established, causation would not have been established: the August 4 headache was most likely a migraine rather than the manifestation of a developing SAH, and a CT scan or lumbar puncture on August 4 would not have detected a bleed that had not yet occurred. The court provided an alternative finding on damages of $50,000 for pain and suffering reduced by half to $25,000 to reflect the portion of the harm that would have occurred regardless of any alleged negligence.
Key authorities: Wilson v Swanson, [1956] SCR 804 (specialist standard); Crits v Sylvester, [1956] OR 132 (medical practitioner standard); ter Neuzen v Korn, [1995] 3 SCR 674 (specialist standard); Snell v Farrell, [1990] 2 SCR 311 (robust and pragmatic causation); Clements v Clements, 2012 SCC 32 (but-for causation framework); Athey v Leonati, [1996] 3 SCR 458 (multiple causes / apportionment); the Ottawa SAH Rule (clinical decision tool for risk stratification of headache patients).
Paul Cahill
Partner, Davidson Cahill Morrison LLP | LSO Certified Specialist in Civil Litigation
Paul represents victims of medical malpractice across Ontario, with trial experience including a $11.5M jury verdict in a birth injury case. He is recognized in Best Lawyers in Canada and serves as trial counsel to other lawyers on complex medical negligence matters.
About PaulMore on medical malpractice in Ontario.
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