Dickson v Pinder: Chiropractic Informed Consent, the “Flippant Patient” Problem, and Whether Spinal Manipulative Therapy Caused a Stroke

Patricia Dickson had a knotted neck and a headache. A neighbour recommended his chiropractor, Dr. Ross Pinder, who had been practising in Fort Saskatchewan, Alberta for over 27 years. She went on February 14, 2002. Dr. Pinder performed spinal manipulative therapy on her neck. She heard a crack. The original pain eased. She went home, made a follow-up appointment, and went to play bingo that evening. In the small hours of February 15 she awoke with a searing pain behind her left eye, profound dizziness, and her left eye “jumping up and down.” Her husband drove her to the emergency room at Fort Saskatchewan’s hospital. She had suffered a stroke.

She sued Dr. Pinder. Her claim was that he had failed to obtain her informed consent before performing the cervical manipulation, and that he had performed it negligently. Four years of litigation and a five-week trial later, Justice K.D. Yamauchi found that Dr. Pinder had breached the informed consent standard, but that the breach hadn’t caused her injury because she would have consented anyway. He also found no negligence in the treatment itself, and concluded on the full causation analysis that the spinal manipulative therapy had not caused the stroke at all. The action was dismissed.

Dickson v Pinder is a significant case in the Canadian informed consent series for several reasons. It extends the Hopp v Lepp and Reibl v Hughes framework to chiropractic practice in detail. It provides one of the clearest judicial analyses of the “flippant patient” problem: the patient who dismisses a risk not because they have understood and accepted it, but because they have not truly understood it. It develops the law on the obligation to disclose alternative treatments. And it engages with a scientific question that continues to be debated in both courts and the medical literature: whether cervical spinal manipulative therapy can cause vertebrobasilar stroke.

The Parties

Patricia Dickson was 50 years old at trial and had lived a physically active working life in Alberta. She had completed grade nine and had some adult literacy upgrading. She acknowledged difficulties with reading comprehension and mathematics. She was obese, at five feet four inches and approximately 275 to 300 pounds. She was a smoker, though she disputed the quantity. Her medical charts recorded varying smoking levels; she testified she smoked one or two cigarettes per week while her charts recorded quantities ranging from one pack per day to one pack per two weeks. She had used birth control pills and hormone replacement therapy at various points in her life. She had a history of periodic neck pain and headaches, previously managed by her family physician. She had undergone several surgical procedures during her adult life, including general anaesthetic operations, and was therefore not unfamiliar with the concept of medical consent.

Dr. Ross Pinder had graduated from Palmer College of Chiropractic in 1975. He had practised in Edmonton for three years and then purchased a Fort Saskatchewan practice in 1978, where he had practised ever since. At the time he treated Ms. Dickson he had 27 years of experience. His primary practice involved spinal manipulative therapy. He was insured through the Canadian Chiropractic Protective Association (CCPA).

The Clinical Events of February 14, 2002

Ms. Dickson’s neck had been “knotted up” for approximately three days before her appointment. The pain was dull and constant; she had experienced similar episodes approximately once every six months over the preceding five years, and had previously managed them through hot showers, heating pads, and occasionally her family physician. This episode she did not seek her family doctor. Ray Maschmeyer, the owner of the land where she and her husband lived, recommended Dr. Pinder. She booked an appointment, then tried to get in the day before, arriving as a walk-in, which the receptionist Reah Mohr confirmed.

On February 14, Ms. Dickson completed a Confidential Patient Personal Record form and an “Informed Consent to Chiropractic Treatment” form in the waiting room. The Informed Consent Form, recommended by the CCPA, specifically stated: “There have been reported cases of injury to a vertebral artery following cervical spinal adjustments. Vertebral artery injuries have been known to cause stroke, sometimes with serious neurological impairment, and may on rare occasion result in serious injury. The possibility of such injuries resulting from cervical adjustment is extremely remote.” She signed the form and was escorted to the examination room.

Dr. Pinder reviewed her forms, took a history, conducted a physical examination including range of motion, blood pressure, orthopaedic and neurological tests (including Houle’s test for vascular or cerebral arterial inhibition, which in Ms. Dickson’s case was negative), and through motion palpation diagnosed that her C6 and C4 vertebrae were not moving smoothly and were “fixated,” causing the suboccipital headache. He proposed spinal manipulative therapy and discussed the risks. He specifically recalled discussing the stroke risk and quoting odds of one in one million to one in two million. His recollection of Ms. Dickson’s reaction was specific: “she was quite flippant about it and I went on to explain that, yes, it could happen to her, that stuff does happen and sometimes it’s not always a lottery.” He did not explain what a stroke was, what its consequences could be, or what alternative treatments existed. Ms. Dickson authorized treatment and Dr. Pinder performed the SMT.

After treatment she felt a different pain and obtained some relief from her pre-treatment neck pain. Dr. Pinder recommended a follow-up in two to three days; she made an appointment for the following week due to her work schedule. She returned home and went to play bingo. Shortly before 2 a.m. on February 15 she awoke with searing pain behind her left eye, dizziness, profuse perspiration, and her left eye “jumping up and down.” She and her husband drove to the Fort Saskatchewan emergency room. She was initially diagnosed with a migraine. On her insistence, she was properly diagnosed with a brain stem stroke and transferred to the University of Alberta Hospital, where an ischemic stroke within the left lateral medulla was confirmed. A CT scan ruled out haemorrhage. She was treated with heparin. Her condition stabilized.

The Legal Framework

Justice Yamauchi set out the four-element negligence framework: duty of care, breach of the standard of care, injury, and causation. Duty was conceded. Injury was not in dispute. The case turned on breach and causation, and breach was itself divided into two distinct questions: whether Dr. Pinder had obtained Ms. Dickson’s informed consent, and whether he had performed the SMT negligently.

The standard of care for chiropractors was drawn from Olsen v Campbell-Jones and Penner v Theobald: “the degree of care, diligence, judgment and skill which is exercised by a normal, prudent or reasonable chiropractor under like or similar circumstances and with the same experience and training.” The Manitoba Court of Appeal’s observation in Penner was adopted: the standard does not vary, but the degree of skill and care required to comply with it is conditioned by the circumstances of each particular case, which are infinitely variable. Because courts have treated chiropractors as medical practitioners for liability purposes, the full body of medical negligence law, including Hopp v Lepp and Reibl v Hughes, applied.

Informed Consent: The Legal Framework Applied

Justice Yamauchi set out the five elements of what a medical practitioner must disclose in obtaining informed consent: the diagnosis of the patient’s condition; the prognosis with and without treatment; the nature of the proposed treatment; the risks associated with the proposed treatment; and the alternatives to the proposed treatment and their risks. The case focused on the last two.

The Risk of Stroke: A Material Risk Requiring Full Explanation

The law on material risks was drawn from Reibl v Hughes, Videto v Kennedy, and White v Turner: a risk is material if it “poses a real threat to the patient’s life, health or comfort,” and even a risk with serious consequences (paralysis or death) must be disclosed even when it is merely possible rather than probable. Mason v Forgie (NBCA) specifically held that the risk of stroke arising from cervical SMT is a material risk requiring disclosure, “particularly bearing in mind the seriousness of the possible consequences.” This Court agreed.

The question was not whether the risk was disclosed; it was. The question was whether it was disclosed in a way that allowed meaningful consent.

Justice Yamauchi found that Ms. Dickson was told the word “stroke,” by the Informed Consent Form and by Dr. Pinder directly. He also found, critically, that she did not understand what a stroke meant. Her “flippant” response (the casual dismissal that struck Dr. Pinder enough that he specifically remembered it eight years later) was not evidence of a patient who understood a serious risk and accepted it. It was evidence of a patient who had heard a word without understanding its meaning. The court drew a careful distinction: it would be very unusual for a person to dismiss casually an extremely negative result without further investigation unless they did not appreciate that it was an extremely negative result.

Justice Yamauchi held that Dr. Pinder had not gone far enough. He did not need to test Ms. Dickson formally, nor to explain the intricacies of vertebral artery dissection. But he should have explained the concept of a stroke and its serious consequences: that a stroke could mean paralysis, permanent neurological impairment, or death. He should have ensured he was comfortable that she understood his explanation. A signed consent form is only legally meaningful if the patient understood the terms she was signing. If she did not understand what “stroke” meant, her signature was meaningless in relation to that risk. Dr. Pinder failed on this point.

Alternative Treatments: A Non-Negotiable Obligation

Both experts agreed that alternative treatments existed for Ms. Dickson’s neck pain: mobilization, massage therapy, trigger point therapy, physiotherapy, or simply waiting, given that her symptoms had resolved on their own before. Dr. Pinder did not routinely discuss alternative treatments with patients for neck pain. He presented SMT as the appropriate therapy and did not canvas options.

Justice Yamauchi found this a clear breach. The Alberta Court of Appeal in Zimmer v Ringrose had established since 1981 that a patient “cannot measure risks in the abstract” and that “to discharge his duty of care, the doctor must give the patient some yardstick against which he can assess the options available to him.” The Saskatchewan Court of Appeal in Haughian v Paine confirmed that the option of conservative treatment or no treatment must be disclosed where circumstances require. The alternatives available to Ms. Dickson, including the realistic possibility that her symptoms would resolve without any intervention, as they had on previous occasions, were not “fringe alternatives.” Dr. Pinder should have presented them.

The Form Does Not Substitute for the Conversation

Dr. Pinder’s practice of having patients sign the Informed Consent Form in the waiting room before any consultation or examination raised a structural concern. Justice Yamauchi addressed it carefully. The form is a useful starting point; it puts the patient on notice that risks exist. But the form must be followed by a genuine consultation that allows the practitioner to explain what those risks mean, tailored to the specific patient and the specific treatment being proposed. As the court observed in Archibald v Kuntz, “the signing of the consent forms by the plaintiff in the hospital on the eve of surgery was a mere formality incapable of satisfying the defendant’s duty of disclosure.” A chiropractor cannot satisfy the duty of informed consent by presenting a form in a waiting room and assuming a signature represents understanding.

Both experts, despite reaching different overall conclusions, agreed on this point: a form alone is insufficient. The chiropractor must discuss the risks directly with the patient, verify understanding, and tailor the explanation to the patient’s level of comprehension.

Informed Consent Causation: She Would Have Consented Anyway

Justice Yamauchi found that Dr. Pinder breached his informed consent obligation on both grounds. The next question, under the modified objective test established in Reibl v Hughes, was whether a reasonable person in Ms. Dickson’s particular position, if properly informed, would have declined the SMT.

The modified objective test asks not what Ms. Dickson personally says she would have done, but what a reasonable person with her specific characteristics and circumstances would have decided. Her testimony was that she would not have consented if told there were other treatments that did not involve “cracking her neck,” and would not have consented if told the treatment could cause serious harm or death. But the court was not bound by her testimony; it was required to evaluate it against the objective circumstances.

The court found that a reasonable person in Ms. Dickson’s particular position would have consented to the SMT even with full disclosure. The supporting analysis:

She was in considerable, persistent pain. This was not a passing discomfort; it had been building for three days and her usual remedies (hot shower, heating pad, family physician) had either not been tried or had not been sought. The fact that she attempted to see Dr. Pinder the day before her scheduled appointment was strong evidence that she wanted immediate relief and was motivated to obtain treatment.

She had a history of making rational medical decisions. In one instance, when offered weight-loss surgery at age 28, she had declined after being fully informed of the risks, including the possibility of death under general anaesthetic. This demonstrated that she was capable of weighing medical risks against benefits and making informed choices. In other cases she had accepted surgery. Her pattern was consistent with a reasonable approach to medical therapy.

Her continued smoking after her stroke, despite knowing it increases the risk of another stroke, was directly relevant. She remained “somewhat flippant” about stroke risk even having experienced one. A reasonable person in her position, one who had already had a stroke, knew the devastating consequences firsthand, knew smoking increased the risk of another, and continued to smoke, would not have declined a chiropractic adjustment to address significant neck pain and headache on the basis of a one-in-a-million stroke risk.

Accordingly: Dr. Pinder’s negligence in obtaining informed consent was not the cause of Ms. Dickson’s injuries. She would have consented regardless. The informed consent claim failed at the causation stage.

Negligent Treatment: No Breach Found

Ms. Dickson alleged that Dr. Pinder was negligent in his diagnosis and in his performance of the SMT itself.

Diagnosis

Justice Yamauchi found that Dr. Pinder’s diagnostic approach (history taking, blood pressure measurement, range of motion testing, orthopaedic and neurological examination, motion palpation) met the standard of a normal, prudent chiropractor in 2002 in the same circumstances. Dr. Carstensen’s criticisms of the records were noted but not accepted as establishing negligence. Dr. Henderson’s conclusion that Dr. Pinder’s clinical approach was consistent with accredited chiropractic education and in keeping with recommended clinical guidelines was accepted. Deficiencies in notes do not automatically establish negligence where the notes do not show a causative connection to the injury.

The SMT

One of the more unusual features of the trial was that at its commencement Dr. Pinder performed a demonstration of his SMT technique on another chiropractor, recorded on DVD. Every expert who viewed the DVD agreed that the demonstrated technique met the standard of care of a normal, prudent chiropractor. Ms. Dickson’s account, that Dr. Pinder had appeared frustrated, had manipulated her arms and chin, and had performed what amounted to a “master cervical adjustment” (a full head-movement technique), was rejected. A “master cervical adjustment” would be a frightening and dangerous procedure, inconsistent with Dr. Pinder’s 27 years of practice and his invariable approach to SMT. The court found the technique as described by Ms. Dickson was highly improbable. Dr. Pinder’s evidence of his invariable practice was accepted. No breach of the standard of care in treatment was established.

Causation: Did the SMT Cause the Stroke?

Having found no actionable negligence, Justice Yamauchi was not required to address causation. He did so nonetheless, observing that if his findings on negligence were wrong, causation would still defeat the claim.

The causation analysis is the most scientifically complex section of the judgment and engages three distinct lines of expert evidence: epidemiological, biomechanical, and clinical.

The Epidemiological Evidence: The Cassidy Study

Dr. J. David Cassidy, an epidemiologist at the Toronto Western Hospital with a background in chiropractic practice and anatomical pathology, presented the “Cassidy Study,” a large population-based case-control and case-crossover study that merged Ontario health insurance data over nine years to compare VBA stroke rates following chiropractic visits and primary care physician visits. The key finding: patients with neck pain and headache diagnoses (the early symptoms of vertebral artery dissection) were at greater risk for VBA stroke after visiting both chiropractors and primary care physicians, but there was no excess risk attributable to chiropractic care specifically.

The study’s conclusion was that patients with a developing arterial dissection were seeking care from chiropractors (and physicians) for the neck pain and headache that dissection causes, and then having their stroke, but that the treatment received did not cause or accelerate the stroke. The temporal association between chiropractic treatment and stroke is explained by the patient presenting with dissection-related symptoms before the stroke occurs, not by the chiropractic treatment triggering the stroke.

Dr. Pinder’s neurological expert, Dr. Adrian Upton of McMaster University, endorsed the Cassidy Study’s findings and concluded that the probable cause of Ms. Dickson’s stroke was her multiple risk factors (obesity, smoking, estrogen use, mild hypertension, borderline diabetes, migraine history, and possibly high cholesterol), not the chiropractic manipulation.

Justice Yamauchi accepted the Cassidy Study as a powerful epidemiological tool while recognizing its limitation: it is a macro-level population study and cannot tell a court definitively whether a specific patient’s stroke was caused by a specific treatment. Following Laferrière v Lawson, the court was not bound by statistical evidence: “the judge’s duty is to assess the damage suffered by a particular patient, not to remain paralyzed by statistical abstraction.” The meteorite analogy, which Dr. Upton himself offered during cross-examination, captured it well: being told that meteorite strikes are statistically improbable does not help the person who was struck by one. Ms. Dickson might have been the statistical exception. The epidemiological evidence showed this was “highly improbable,” but the central causation question still turned on the specific facts of her case.

The Biomechanical Evidence: The Cadaver Study

Dr. Bruce Symons, who had researched vertebral artery biomechanics under Dr. Walter Herzog at the University of Calgary, presented the “Cadaver Study,” a study of forces exerted on vertebral arteries during SMT performed on five cadavers (ages 80 to 99). The study found that SMT exerted forces of approximately 100 to 150 Newtons (equivalent to a light slap, compared to approximately 3,000 Newtons for a karate chop to break a brick) and that the vertebral arteries in cadavers experienced essentially no force during this manipulation because of their slack and their enclosure within bony canals.

Justice Yamauchi accepted the Cadaver Study as relevant but acknowledged its significant limitations: cadavers lack blood pressure and live tissue response, the study used only five elderly cadavers, and academic commentary had raised questions about its conclusions. The Cadaver Study suggested with some force that SMT could not cause vertebral artery dissection through mechanical force, but the court could not accept this as definitive given the study’s limitations and Dr. Woolfenden’s criticisms. Like the Cassidy Study, it established that SMT-caused stroke was highly unlikely rather than impossible.

The Clinical Evidence: Did Ms. Dickson Have an Arterial Dissection?

The proposed mechanism linking SMT to stroke was arterial dissection: the SMT tears or injures the vertebral artery, causing a clot to form at the injury site, which then travels to the brain and causes a stroke. Two sites of possible arterial abnormality were identified in Ms. Dickson’s imaging:

The intracranial V4 abnormality: Dr. Ashforth, the treating neuroradiologist who performed the angiography, concluded this was “developmental,” a congenital narrowing, rather than a dissection. Drs. Upton and Rosso agreed. Dr. Rosso further noted that if this had been an actual dissection and Ms. Dickson had been treated with heparin (as she was), the dissection’s false lumen would have been exposed to blood pressure with each heartbeat, likely causing deterioration or rupture, which did not occur. The behaviour of the abnormality under treatment was inconsistent with dissection.

The V1/V2 “flap” abnormality: Dr. Ashforth observed a “shelf-like defect” and described it as “highly suspicious for a small left focal vertebral artery dissection.” Dr. Woolfenden and Dr. Hu concluded it was a dissection caused by the chiropractic manipulation. However, Dr. Rosso, whose analysis Justice Yamauchi found most persuasive, concluded the apparent abnormality was visible on only one imaging plane, with other planes showing the same region as smooth. A genuine arterial dissection would be visible from multiple angles; an appearance visible in only one plane is an artifact of viewing angle (a “double density” superimposition), not an actual injury.

Dr. Buchan and Dr. Hu were both criticized for the quality of their reasoning. Dr. Hu had reached inconsistent conclusions across his reports (characterizing the same abnormality as both catheter-induced vasospasm and as dissection) and Justice Yamauchi found he was acting as an advocate for Ms. Dickson rather than an independent expert.

Justice Yamauchi concluded that Ms. Dickson had not suffered an arterial dissection at either site. Since dissection was the proposed mechanism through which SMT could cause stroke, the absence of dissection meant the SMT did not cause the stroke. The court accepted Dr. Upton’s analysis: the most likely cause of Ms. Dickson’s stroke was her cumulative risk factors, which in combination were “more likely than not” to have caused a spontaneous stroke event unrelated to the chiropractic treatment. On the but-for test, which applied because this was not a case where but-for causation was impossible, only a case where the evidence conflicted, Ms. Dickson had not established that but for the SMT she would not have suffered her stroke.

The action was dismissed with costs to Dr. Pinder.

What Dickson v Pinder Establishes

Principle One: Chiropractors Are Held to the Same Informed Consent Standard as Other Medical Practitioners

Dickson v Pinder confirms that the full informed consent framework from Hopp v Lepp and Reibl v Hughes applies to chiropractors with equal force as to physicians and surgeons. The five disclosure obligations (diagnosis, prognosis with and without treatment, nature of the proposed treatment, its risks, and the alternatives) apply to chiropractic consultation. This is not a reduced standard for “non-medical” practitioners. Chiropractors who treat conditions that carry risks of serious injury (including stroke from cervical SMT) must disclose those risks in a manner that allows genuinely informed consent.

Principle Two: The “Flippant Patient” Problem — Disclosure Is Not Understanding

The most instructive contribution of Dickson v Pinder to the informed consent series is its treatment of what Justice Yamauchi implicitly characterizes as the “flippant patient” problem. Dr. Pinder mentioned the word “stroke.” Ms. Dickson’s reaction was casual dismissal. He noted her flippancy and corrected her: it could happen to you. She remained dismissive.

The court found that her flippancy was not evidence of understanding and acceptance; it was evidence of non-comprehension. A person who genuinely understands that a treatment carries a risk of permanent paralysis or death does not casually dismiss that risk. Flippancy in the face of a serious disclosed risk is a clinical signal that the disclosure has not achieved understanding. The chiropractor must respond to that signal by explaining more (what a stroke is, what it does, what it means for a life), not by accepting the dismissal as consent. As the court put it: “It would be very unusual for a person to dismiss casually an extremely negative result, without further investigation of that result, including the details of that result and other contributory risk factors.”

This principle has implications beyond chiropractic: wherever a patient appears to dismiss or minimize a disclosed serious risk, the practitioner has an obligation to probe whether this reflects genuine understanding or whether it reflects an absence of comprehension that must be addressed before consent can be obtained.

Principle Three: Alternative Treatments Must Be Disclosed — Always

Dickson v Pinder reaffirms the Alberta Court of Appeal’s position since Zimmer v Ringrose (1981): the obligation to disclose alternative treatments is not optional or conditional on patient apprehension. The patient “cannot measure risks in the abstract.” The practitioner must give the patient a yardstick against which to assess the proposed therapy, including conservative options, non-chiropractic options, and the option of doing nothing. A patient who presents with a periodic, self-resolving neck pain condition that has previously resolved on its own is entitled to know that the condition may resolve without any intervention. Dr. Pinder’s practice of not routinely discussing alternatives was, without qualification, a breach of his duty of disclosure.

Principle Four: A Signed Consent Form Is Not Informed Consent

The presence of a signed informed consent form, even one that mentions the specific risk that materialized, does not satisfy the duty of disclosure unless the patient understood the content of what they signed. If Ms. Dickson did not know what “stroke” meant, her signature on a form that mentioned stroke risk was meaningless. The form is the starting point of the consent process, not its conclusion. The practitioner must build on the form through direct consultation and must satisfy themselves that the patient has understood the material information before proceeding.

Principle Five: The Modified Objective Causation Test — Patient Circumstances Are Decisive

Dickson v Pinder illustrates how the modified objective test from Reibl v Hughes operates in practice. The question is not whether the plaintiff personally would have declined; testimony to that effect is given but is not conclusive. The question is whether a reasonable person in the plaintiff’s particular position, with her specific circumstances, characteristics, and motivations, would have declined. Here, the circumstances overwhelmingly favoured a finding that she would have consented: she was in pain and determined to obtain treatment, she had a pattern of rational medical decision-making (including declining surgery when informed of its risks), and she remained cavalier about stroke risk even after experiencing one. The breach of informed consent was real, but it was causally inert.

Principle Six: Epidemiological Evidence Is a Tool, Not a Verdict

Justice Yamauchi’s treatment of the Cassidy Study is a methodologically important contribution to the use of population-based statistical evidence in personal injury litigation. The Study was powerful evidence that, at the population level, chiropractic treatment does not cause VBA stroke at a rate exceeding baseline risk. But it could not answer the question the court was required to answer: whether this patient’s stroke was caused by this chiropractor’s treatment. Following Laferrière v Lawson, statistical abstraction cannot substitute for analysis of the individual patient’s facts. The epidemiological evidence informed the court’s reasoning (it established that SMT-caused stroke was highly improbable), but the ultimate determination was made by analyzing the specific imaging findings, the specific risk factors, and the specific circumstances of Ms. Dickson’s case.

Principle Seven: The But-For Test Applies Unless Causation Is Structurally Impossible

The competing expert opinions on whether SMT caused Ms. Dickson’s stroke did not render the but-for test unworkable. Conflicting theories are not the kind of structural impossibility that justifies resort to the material contribution test; they require the court to weigh the evidence and reach a conclusion. Following Resurfice Corp v Hanke and the Alberta Court of Appeal, material contribution applies where it is impossible to establish causation using but-for due to factors outside the plaintiff’s control (such as the limits of current scientific knowledge in a multi-tortfeasor case). This was not such a case. The court weighed the evidence, concluded Ms. Dickson had not suffered an arterial dissection, accepted that her multiple risk factors were the more probable cause of her spontaneous stroke, and dismissed the claim on but-for.

Dickson v Pinder in the Informed Consent Series

Dickson v Pinder belongs in the Informed Consent category of this series as an application and extension of the principles established in Hopp v Lepp, 1980 CanLII 14 (SCC), [1980] 2 SCR 192 — https://canlii.ca/t/1mjv6, and Reibl v Hughes, 1980 CanLII 23 (SCC), [1980] 2 SCR 880 — https://canlii.ca/t/1mjvr. Both foundational cases are directly cited and applied. Arndt v Smith, 1997 CanLII 360 (SCC), [1997] 2 SCR 539 — which refined the modified objective test — is also applied.

The case is also relevant to the Causation category for its detailed treatment of the epidemiological versus clinical causation distinction, the limitations of population statistics in individual cases, and the proper application of the but-for test in the face of conflicting expert theories. Snell v Farrell, 1990 CanLII 70 (SCC), [1990] 2 SCR 311 — https://canlii.ca/t/1fstw is directly applied on causation, and Wilson v Swanson, [1956] SCR 804 is quoted on the variability of individual human physiology.

Dickson v Pinder also adds geographic and practice-area diversity to this series. It is the only Alberta case in the series, the only case involving a chiropractor as defendant, and the only case that addresses the chiropractic SMT, stroke causation question through a full review of both epidemiological and biomechanical expert evidence.

Quick Reference: Dickson v Pinder

Case Details

• Dickson v. Pinder, 2010 ABQB 269 (CanLII), 489 AR 54 — https://canlii.ca/t/29czc | Docket 0403 02817 | Registry: Edmonton | Justice K.D. Yamauchi | April 19, 2010
• Court of Queen’s Bench of Alberta | Action dismissed with costs to Dr. Pinder

The Parties

• Plaintiff: Patricia Dickson, 50 years old at trial; obesity; smoker; limited formal education; prior neck pain previously managed by family physician; first-time chiropractic patient
• Defendant: Dr. Ross J. Pinder, chiropractor, Fort Saskatchewan, Alberta; practising since 1975 (27 years at time of treatment); primary practice: SMT; CCPA-insured

The Clinical Facts

• February 14, 2002: Ms. Dickson presented with 3-day neck pain and headache; first chiropractic visit ever; had attempted to see Dr. Pinder the previous day as walk-in
• Informed Consent Form signed in waiting room before consultation; mentioned stroke risk
• Dr. Pinder: history, physical exam, orthopaedic and neurological testing, diagnosis (C4 and C6 fixation), proposed and performed cervical SMT
• Post-SMT: different pain noted; some relief from original pain; follow-up appointment made
• February 15, ~1:45 a.m.: searing pain behind left eye, dizziness, profuse perspiration, eye “jumping up and down”
• Emergency room Fort Saskatchewan: initially diagnosed migraine; on her insistence, diagnosed stroke and transferred to University of Alberta Hospital
• Ischemic stroke within left lateral medulla confirmed; treated with heparin

Informed Consent — Breach Found (Two Grounds)

• Ground 1, Failure to explain stroke: Dr. Pinder mentioned the word “stroke” and quoted the statistical probability (1 in 1-2 million). He did NOT explain what a stroke is, its consequences, or the nature of the risk. Ms. Dickson’s “flippant” response was evidence not of understanding and acceptance but of non-comprehension; a person who understands a risk of paralysis or death does not casually dismiss it. The signed form was meaningless if she did not understand the term.
• Ground 2, Failure to disclose alternatives: Dr. Pinder did not routinely discuss alternative treatments and did not do so with Ms. Dickson. Alternatives existed (mobilization, massage therapy, physiotherapy, doing nothing) that were not “fringe” options. Given that her symptoms had previously resolved on their own, the option of no treatment was particularly relevant. The Alberta Court of Appeal has required disclosure of alternatives since Zimmer v Ringrose (1981).
• Signed consent form: insufficient on its own; the duty requires direct consultation and verification of understanding, not merely a signature obtained in a waiting room

Informed Consent — Causation Failed (Modified Objective Test)

• Test: What would a reasonable person in Ms. Dickson’s particular position have decided if properly informed?
• Finding: She would have consented anyway; the breach was causally inert
• Reasons: In pain and determined to receive immediate treatment (attended the day before her appointment); had a rational approach to medical decisions (had previously declined surgery when informed of death risk, but accepted surgery in other cases); remained “somewhat flippant” about stroke risk even after having one; continued to smoke despite knowing it increased stroke risk; no evidence that further disclosure would have changed her decision

Negligent Treatment — No Breach

• Diagnosis: appropriate history and physical examination; Houle’s test done (though later recognized as having poor predictive value); chart notes acceptable; Dr. Henderson’s expert opinion accepted that diagnostic approach met the standard of a prudent chiropractor in 2002
• SMT technique: Dr. Pinder demonstrated his technique on DVD at trial; all experts agreed the demonstrated technique met the standard of care; court rejected Ms. Dickson’s account of a “master cervical adjustment” and alleged frustration as highly improbable given Dr. Pinder’s 27 years of experience; invariable practice evidence accepted

Causation — SMT Did Not Cause the Stroke

• Epidemiological: The Cassidy Study (population-based, Ontario, 9 years) found no excess VBA stroke risk attributable to chiropractic care vs. primary care physician visits; the association between chiropractic visits and VBA stroke is explained by patients presenting to chiropractors with dissection-related neck pain/headache before their spontaneous stroke, not because the treatment caused the stroke. Highly improbable the SMT caused Ms. Dickson’s stroke, but not the decisive clinical question.
• Biomechanical: The Cadaver Study found SMT force (~100-150N) insufficient to dissect vertebral arteries; court accepted this as relevant but acknowledged its limitations (elderly cadavers, no blood pressure, academic controversy)
• Clinical, V4 intracranial abnormality: Accepted as congenital narrowing, not dissection; supported by Dr. Ashforth (treating neuroradiologist), Drs. Upton and Rosso; behaviour under heparin treatment inconsistent with active dissection
• Clinical, V1/V2 “flap” abnormality: Dr. Rosso accepted that the abnormality was visible on one imaging plane only; a genuine dissection would be visible from multiple angles; the “double density” was an artifact of viewing angle, not an actual arterial injury
• Ms. Dickson’s multiple risk factors: obesity, smoking, estrogen use, mild hypertension, borderline diabetes, migraine history, possible high cholesterol; “when you have multiple risk factors, they become cumulative” (Dr. Upton); probable cause of the stroke was the cumulative risk factors, not the SMT
• But-for test applied (not material contribution): conflicting expert opinions do not make but-for “impossible”; they require weighing; no structural impossibility equivalent to the multi-tortfeasor problem
• Conclusion: But for Ms. Dickson’s multiple risk factors, she would not have had her stroke. The SMT did not cause the stroke. Action dismissed.

Key Legal Principles

• Standard of care for chiropractors: same principles as other medical practitioners; “degree of care, diligence, judgment and skill of a normal, prudent or reasonable chiropractor under like or similar circumstances” (Olsen, Penner)
• Informed consent applies fully to chiropractors: five-element disclosure obligation (diagnosis, prognosis, nature, risks, alternatives) from Hopp and Reibl applies with equal force
• Stroke from cervical SMT is a material risk requiring disclosure: Mason v Forgie (NBCA); rare but serious consequences require disclosure regardless of low probability
• Disclosure requires understanding: a signed form is meaningless if the patient did not understand the terms; chiropractor must explain the meaning and consequences of identified risks, not merely name them
• “Flippant” patient response is a warning signal: casual dismissal of a serious disclosed risk signals non-comprehension, not informed acceptance; the practitioner must verify understanding before proceeding
• Alternative treatments must always be disclosed: Zimmer v Ringrose (1981 ABCA); patient cannot make an informed choice without a yardstick against which to assess the options; includes conservative and no-treatment options where appropriate
• Modified objective causation test (Reibl v Hughes): patient circumstances (pain level, eagerness for treatment, medical history, patterns of decision-making) are decisive; plaintiff’s testimony about what they would have done is relevant but not conclusive
• Epidemiological statistics inform but do not determine individual causation: Laferrière v Lawson — “the judge’s duty is to assess the damage suffered by a particular patient, not to remain paralyzed by statistical abstraction”
• But-for test applies unless causation is structurally impossible: conflicting expert theories require weighing, not abandonment of the but-for standard in favour of material contribution
• Invariable practice evidence is admissible: Belknap v Meakes (BCCA); where a practitioner cannot recall a specific encounter, reliable evidence of their habitual practice is admissible as a substitute for specific recollection

Key Cases Referenced

• Hopp v. Lepp, 1980 CanLII 14 (SCC), [1980] 2 SCR 192 — https://canlii.ca/t/1mjv6 — foundational informed consent disclosure framework; article in this series
• Reibl v. Hughes, 1980 CanLII 23 (SCC), [1980] 2 SCR 880 — https://canlii.ca/t/1mjvr — modified objective causation test for informed consent; article in this series
• Arndt v. Smith, 1997 CanLII 360 (SCC), [1997] 2 SCR 539 — SCC refinement of the modified objective test
• Snell v. Farrell, 1990 CanLII 70 (SCC), [1990] 2 SCR 311 — https://canlii.ca/t/1fstw — causation by inference; robust pragmatic approach; article in this series
• Zimmer v. Ringrose, 1981 ABCA 60 — Alberta Court of Appeal; obligation to disclose alternative treatments
• Haughian v. Paine, 1987 CanLII 987 (SK CA) — disclosure obligation includes conservative and no-treatment alternatives
• Mason v. Forgie, 1986 CanLII 3928 (NB CA) — stroke from cervical SMT is a material risk requiring disclosure
• Wilson v. Swanson, 1956 CanLII 1 (SCC), [1956] SCR 804 — “the dynamics of the human body of each individual are themselves individual”; article in this series
• Resurfice Corp. v. Hanke, 2007 SCC 7, [2007] 1 SCR 333 — but-for is the basic causation test; material contribution applies only in specific exceptional circumstances
• Laferrière v. Lawson, 1991 CanLII 87 (SCC), [1991] 1 SCR 541 — statistical evidence does not replace individual causation analysis
• Olsen v. Campbell-Jones, 2009 ABQB 371 — chiropractic standard of care; companion Alberta chiropractic case

Related Articles in This Series

• Hopp v. Lepp, [1980] 2 SCR 192 — https://canlii.ca/t/1mjv6 — foundational disclosure duty; the specific-questions rule; article in this series
• Reibl v. Hughes, [1980] 2 SCR 880 — https://canlii.ca/t/1mjvr — the modified objective causation test for informed consent claims; article in this series
• Snell v. Farrell, [1990] 2 SCR 311 — https://canlii.ca/t/1fstw — the robust pragmatic approach to but-for causation; article in this series
• Clements v. Clements, 2012 SCC 32 — https://canlii.ca/t/frvld — when material contribution applies; but-for as the general rule; article in this series
• Wilson v. Swanson, [1956] SCR 804 — the error of judgment doctrine; the specialist standard; quoted in this case; article in this series