“Analogy” as defined at www.oxforddictionaries.com:

1.  a comparison between one thing and another, typically for the purpose of explanation or clarification: ..

…

1.3 … Logic a process of arguing from similarity in known respects to similarity in other respects: …

So, tell me again, please:  Why is a raven like a writing desk?

[246]     As I interpret Clements, it is my responsibility to determine whether on the totality of the evidence, and taking “a robust common sense” approach to causation, I am satisfied on a balance of probabilities that “but for” the negligence of Dr. Edington, Ms. Boyd would not have suffered a debilitating stroke.

Boyd et al. v. Edington, 2014 ONSC 1130

[1]       On December 27, 2008, Danielle Boyd, (“Ms. Boyd”) age 24, went bowling.  She was taking medication for high blood pressure (“BP”) and had recently been suffering from severe headaches. She was feeling sick and a friend drove her from the bowling alley to Hanover Hospital just after 22:00.  On arrival, her symptoms included left-sided numbness, unsteadiness on her feet, speech garbled at times, involuntary eye movement and headache. Her BP was elevated.  Ms. Boyd was at Hanover Hospital from the evening of December 27 to the morning of December 28, and I will not repeat references to the date and year.

[2]       Dr. Edington saw Ms. Boyd immediately. He considered possible diagnoses of “HTN” (meaning hypertensive crisis), “migraine equivalent” and alcohol use. He kept her in hospital for observation and administered medication to lower her BP.

[3]       The attending nurse recorded at 02:30 that Ms. Boyd was unable to move her left arm at all, was drowsy and complained of being very dizzy with movement. The nurse advised Dr. Edington of the change in Ms. Boyd’s condition.  Dr. Edington was resting at that time and he did not reassess her.

[4]       Dr. Edington did reassess Ms. Boyd at 05:30.  By 06:45, Ms. Boyd’s signs had worsened and her left leg was now less mobile. At 07:00, Dr. Edington contacted the neurology department at London Heath Services Centre (“LHSC”) and arrangements were made to transfer her.

[5]       Ms. Boyd arrived at LHSC at 09:40 on December 28.  By 12:30, imaging revealed that she had a dissection of her right vertebral artery (“RVA”).  The dissection extended from near the top of her spinal cord into her cranium. A “dissection” means that the arterial layers have separated and blood enters or bleeding occurs between the layers.  The artery wall expands and it can narrow or block the artery. Dissections often result in blood clots which can block arteries.  At 13:13, Ms. Boyd was administered heparin, an anticoagulant used to try to prevent the formation of blood clots.

[6]      Ms. Boyd’s condition was stable until approximately midnight on December 29. At that time, her condition deteriorated abruptly. She suffered a stroke, which killed the tissue in her upper spinal cord and lower brain stem.  When I refer in these reasons to Ms. Boyd’s “stroke”, I am referring to this major stroke.

[7]       Ms. Boyd submits that:

(a)      Dr. Edington was negligent in failing to recognize the signs of stroke, and in failing to contact LHSC and arrange for her transfer eight hours earlier;

(b)      Dr. Edington’s lowering of her BP exacerbated what were minor transient symptoms, and created conditions conducive to blood clot formation;

(c)      the immediate cause of the stroke was a blockage caused by a blood clot; and

(d)      but for the lowering of her BP, and the approximate eight hour delay in administering heparin, she would not have suffered a debilitating stroke.

 [8]       Dr. Edington submits that:

(a)      he met the standard of care by treating Ms. Boyd for high BP and observing her overnight;

(b)      in any event, an extension of the dissection of the artery wall caused the blockage and not a blood clot. (It is agreed that heparin is not effective to treat a dissection and that lowering BP would not cause a dissection to extend. As such, if the stroke was caused by the dissection, this action must be dismissed);

(c)      even assuming the stroke was caused by a blood clot, the reduction in Ms. Boyd’s BP in Hanover did not cause or contribute to the formation of blood clots; and

(d)      even assuming the stroke was caused by a blood clot, the weight of scientific opinion is that heparin is not recommended for treating vertebral artery dissection (“VAD”) and should not be administered. As such, any delay in administering non-recommended treatment cannot cause damage.

….

[237]             In my opinion this case is analogous to Clements, in which the plaintiff, Ms. Clements, was a passenger on a motorcycle operated by her husband.  Mr. Clements was not aware a nail had lodged in one tire.  The motorcycle was overloaded by 100 pounds and being driven 20 kph over the speed limit at the time the nail dislodged and the tire deflated rapidly.  Mr. Clements lost control of the motorcycle resulting in a crash and severe injury to Ms. Clements.

[238]             In that case there were three factors to consider:

(a)      the no-fault factor being the nail that fell out of the tire causing rapid deflation;

(b)      the at fault factor that the defendant was driving 20 kph too fast; and

(c)      the at fault factor that the defendant overloaded the motorcycle by 100 pounds.

 [239]             The Supreme Court of Canada noted at para. 48 that the trial judge accepted expert evidence that:

[A]fter the fact, it is not possible through accident reconstruction modelling to determine at what combination of lower speed and lesser weight recovery from the weave instability would have been practicable.

 [240]             Further, the court held that the trial judge erred in reasoning that because expert scientific evidence could not determine the interplay of these three factors, the plaintiff could not prove “but for” causation.

[241]             Chief Justice McLachlin for the majority stated, at para. 49:

         As discussed above, the cases consistently hold that scientific precision is not necessary to a conclusion that “but for” causation is established on a balance of probabilities.  It follows that the trial judge erred in insisting on scientific precision in the evidence as a condition of finding “but for” causation.

 [242]             Chief Justice McLachlin referred to the fact that:

(a)      instability would increase with higher speed;

(b)      instability would increase with overloading;

(c)      the judge was left with no scientific evidence one way or the other as to whether the accident would have occurred absent the excessive speed and overloading; and

(d)      ordinary common sense supported the relation between the excessive speed and weight and the injury.

[243]             The factors in our case are:

(a)      the no fault factor being the VAD Ms. Boyd suffered can initiate the clotting process;

(b)      the at fault factor that Ms. Boyd’s BP was lowered drastically which I have found created conditions that promoted clot formation and growth; and

(c)      the at fault factor that the administration of heparin, which inhibits the formation and growth of blood clots, was delayed by eight hours.

[244]             As in Clements, there is no scientific test or model which can determine one way or the other whether the clot that caused Ms. Boyd’s stroke would have formed and grown to the size it did if Ms. Boyd’s BP [blood pressure: DC] had not been lowered and if heparin was administered earlier.

[245]             As in Clements, ordinary common sense supports the relation between conditions promoting clot formation and growth, late administration of heparin which inhibits clot formation and growth and Ms. Boyd’s stroke which was caused by a clot.

[246]             As I interpret Clements, it is my responsibility to determine whether on the totality of the evidence, and taking “a robust common sense” approach to causation. I am satisfied on a balance of probabilities that “but for” the negligence of Dr. Edington, Ms. Boyd would not have suffered a debilitating stroke.