The first issue to be decided is whether the commission’s order was appealable. Where an appeal may be taken from an order of the commission, an action in mandamus may not be maintained. State, ex rel. Benton, v. Columbus & Southern Ohio Elec. Co. (1968), 14 Ohio St. 2d 130 [43 O.O.2d 238], paragraph one of the syllabus. Since R.C. 4123.519 provides that decisions of the commission, other than those as to the extent of disability, are appealable, we must determine whether the decision which is the subject of this mandamus action was “as to extent of disability” so that a mandamus action properly lies.
The commission determined that claimant was not entitled to additional compensation for the industrial injury suffered October 3, 1978. This court recently held that a decision of the commission which goes to a claimant’s right to participate in the fund is appealable; however, a decision which merely extends the period of time for which a claimant will receive benefits concerns the extent of disability and is not appealable. Gilbert v. Midland-Ross Corp. (1981), 67 Ohio St. 2d 267 [21 O.O.3d 168], paragraph one of the syllabus. Here, claimant’s right to participate in the fund as a result of his October 3, 1978 injury was determined in a previous decision not before this court. The November 12,1980 commission order refused to extend the period of time for which claimant would receive benefits. Applying the language in the Gilbert opinion quoted above, it is apparent such a decision concerns extent of disability and is not appealable. Therefore, an action in mandamus is appropriate.1
*100Given the appropriateness of mandamus in this case, we must next determine if the commission abused its discretion by denying claimant’s motion for additional compensation. In support of his petition, claimant contends certain misstatements in Dr. Meyer’s report impugns its reliability, so that it must be discounted as evidence. Further, claimant maintains Dr. Braunlin’s report cannot be considered as evidence. Rather, claimant urges that only his own physician, Dr. Longert, presented a report on which the commission may rely.
The evidence before the commission consisted of three physicians’ reports, those of Drs. Longert, Meyer and Braunlin. Both Drs. Meyer and Braunlin concluded that the acute extrusion of a lumbrosacral disc from which claimant suffered occurred at the time of the home episode, and not as a result of the 1978 accident at work. Even claimant’s own doctor, Dr. Longert, did not dispute that his condition may have been caused by factors other than the industrial injury. His report concluded, in part:
“It is my opinion that the patient’s present condition certainly is a recurrence or exacerbation of his previous condition. The industrial claim, which was allowed in 1978, for recurrent injury to his back was without question at least contributing, if not the only contributing factor, to his subsequent radiculopathy, which was recognized approximately one year later. * * *”
Our examination of the reports before the commission leads to the conclusion that reliable, probative and substantial evidence in accordance with the law exists to support a factual finding and determination that claimant’s period of disability did not result from his industrial injury of 1978. The claimed errors in the report of Dr! Meyer do not rise to such a level as to impute prejudice or unreliability on his part. Nor does Dr. Longert’s report require the commission to conclude that the period of subsequent disability was merely an extension of the previous disability caused by the industrial injury. Accordingly, there was no evidence to support claimant’s contention that the commission abused its discretion by denying his motion for additional com*101pensation, and the judgment of the court of appeals denying the requested writ is hereby affirmed.
Judgment affirmed.
Celebrezze, C.J., W. Brown, Sweeney and Locher, JJ., concur.Cross-appellant vigorously argues that this case is controlled by paragraph two of the syllabus in Gilbert, which states:
*100“A decision to reactivate a previously allowed claim now dormant, when there has been an intervening trauma, is, in effect, a decision going to claimant’s right to participate in the fund for an injury or impairment not previously claimed or passed upon and is appealable.”
The instant case however, is distinguishable from the situation addressed in Gilbert. In that action, the claimant suffered an injury at work after returning from a period, of disability for a previous work-related injury. He filed a new claim for the second injury and sought to reactivate the earlier claim. Here, claimant suffered an exacerbation at home of his previous injury, and filed a motion for modification of the compensation order in the 1978 injury claim. There were not two separate work-related accidents or accident claims, as in Gilbert. That decision emphasized that when an intervening trauma arising from a second industrial accident results in an attempt to reactivate an earlier, dormant claim, the worker seeks, in effect, a decision granting the right to participate for an injury or impairment not previously claimed or passed upon. Gilbert, supra, at 272. Claimant here did not assert that an intervening trauma or later compensable claim exists. Rather, he sought a determination that the back injury sustained in 1978 was more serious than originally claimed, resulting in an additional period of disability. Such a claim is one as to extent of disability.