In Bisei v. Workmen's Compensation Appeal Board (Tower Lines, Inc.), 61 Pa. Commw. 260, 433 A.2d 592 (Pa. Cmwlth. 1981), two physicians testified but neither could offer a diagnosis for the claimant's symptoms. One stated he could only assume that they were related to the recent accident because they coincided with its occurrence, and the other repeatedly stated that he did not have an opinion on the etiology of the claimant's symptoms.