What is the test for causation in medical malpractice?

In Laferriere v. Lawson (1991) 1991 CanLII 87 (SCC), 78 D.L.R. (4th) 609 (S.C.C.) Mr. Justice Gonthier produced a summary of general observations applicable to causation in medical malpractice, (at p.658). “-The rules of civil responsibility require proof of fault, causation and damage. -Both acts and omissions may amount to fault and both may be analyzed similarly with regard to causation. -Causation in law is not identical to scientific causation. -Causation in law must be established on the balance of probabilities, taking into account all the evidence; factual, statistical and that which the judge is entitled to presume. -In some cases where a fault presents a clear danger and where such danger materializes, it may be reasonable to presume a causal link, unless there is a demonstration to the contrary. -Statistical evidence may be helpful as indicative but is not determinative. In particular, where statistical evidence does not indicate causation on the balance of probabilities, causation in law may nonetheless exist where evidence in the case supports a finding. -Even where statistical and factual evidence do not support a finding of causation on the balance of probabilities with respect to particular damage (ie. death or sickness) such evidence may still justify a finding of causation with respect to lesser damage (ie. slightly shorter life, greater pain). -The evidence must be carefully analyzed to determine the exact nature of the fault or breach of duty and its consequences as well as the particular character of the damage which has been suffered, as experienced by the victim. -If after consideration of these factors a judge is not satisfied that the fault has, on his or her assessment of the balance of probabilities, caused any real damage, then recovery should be denied.”