Is an expert opinion required to start the limitations period running in a medical negligence action?

In McSween v. Louis a burn was noticed after surgery. The plaintiff did not sue until she had obtained an expert opinion that the burn was a result of the surgery. Feldman J.A held at para. 36 that this was a case where an expert opinion was not needed to start the limitations period running. At paras. 47 and 48, he distinguished actions that require an expert opinion to start the limitations period running and those that do not: In some situations, often where an injury occurs and manifests itself immediately, for example during a medical procedure such as an operation, the patient knows that the injury must have been caused through some act or failure to act by one or more of the professionals involved in the procedure and there was the likelihood of negligence of some kind, either in what was done or what was not done but should have been. In other situations the patient either learns that he or she has suffered an injury, but does not know whether it occurred during or as a result of a medical procedure, or learns of an untimely diagnosis of a disease. In those situations, the patient requires the assistance of experts to advise whether the injury was suffered because of something which occurred during a past medical procedure, or whether there was at some point a misdiagnosis of symptoms which could and should have been noted earlier.