What is the test for determining which accident benefit insurer is responsible for payment of fibromyalgia benefits?

In Pisani v. Simcoe & Erie General Insurance Co., [1994] O.I.C.D. No. 129, upheld [1995] O.I.C.D. No. 201*, the applicant was injured as a result of two accidents in which two different accident benefit insurers were responsible for payment benefits. In that case, the arbitrator held, despite the fact that the insured testified that the second accident was the more severe of the two accidents, that the first insurer was responsible for payment of them because the second accident was not believed to have caused additional injuries. The arbitrator held that it was very difficult to determine which accident or accidents significantly contributed to the applicant’s fibromyalgia. The arbitrator accepted that both accidents aggravated the applicant’s symptoms and contributed to the subsequent development of fibromyalgia, but was not satisfied that they significantly contributed to the severity or duration of the applicant’s symptoms. This decision was upheld on appeal. * My analysis of the cases in the next two pages is set out at the conclusion of the defendant’s submissions.