In Benson v. Workers' Comp. Appeals Bd. (2009) 170 Cal. App. 4th 1535, where the WCJ adjudicated a specific neck injury and cumulative neck injury in the same proceeding, the court explained that even though the statute speaks in terms of a "prior award," apportionment is required where successive injuries become permanent at the same time: "Apportionment is required for each distinct industrial injury causing a permanent disability, regardless of the temporal occurrence of permanent disability or the injuries themselves. ... The only relevant inquiry is whether separate and distinct industrial injuries have been sustained. If so, 'then each injury must stand on its own.' " (Id. at p. 1559.) "The plain language of the current statutory scheme requires apportionment to each cause of a permanent disability, including each distinct industrial injury." (Id. at p. 1549.) In that case, an employee sustained a specific industrial injury to her neck on June 3, 2003. She eventually underwent surgical fusion of the cervical spine. in September 2005, Dr. Izzo, acting as an AME, concluded that the employee had actually sustained two separate injuries to her neck, the specific injury and a cumulative trauma injury through June 3, 2003, and that both injuries became permanent and stationary on the same date. Dr. Izzo apportioned half of the employee's permanent disability to the cumulative trauma injury and half to the specific injury. (Benson, supra, 170 Cal.App.4th at p. 1540.) The employee filed two separate claims for her injuries and it was undisputed that the employee's combined permanent disability rating as a result of her injuries was 62 percent. The WCJ issued the employee a single permanent disability award based on the combined permanent disability rating, rather than two separate awards of 31 percent permanent disability. (Id. at p. 1541.) The board granted the employer's petition for reconsideration, and concluded, en banc, that " 'based upon the AME's determination that each of the employee's two injuries was equally responsible for her current level of permanent disability, she is entitled to receive a separate award of 31% permanent disability for each injury.' " (Ibid.) The employee filed a petition for writ of review. The appellate court held that "the plain language of sections 4663 and 4664 compels apportionment here." (Benson, supra, 170 Cal.App.4th at p. 1549.) "The Legislature's focus, in section 4663, subdivision (c), on apportionment to other causative factors, 'including prior industrial injuries,' rather than prior permanent disabilities, must be accorded significance." (Id. at p. 1550.) When an injured employee has a prior industrial injury, but never received an award of permanent disability resulting from that injury, a physician could still determine, as a matter of fact, that the injured worker's present level of permanent disability was partially caused by the previous industrial injury. (Id. at pp. 1550-1551, fn. 14; see also Kopping v. Workers' Comp. Appeals Bd., supra, 142 Cal.App.4th at p. 1112.) When that occurs, the " 'merging of separate injuries into a single award of disability, is contrary to the reforms set in place by SB 899, which mandate that an employer cannot be held liable for any disability other than that directly caused the by the industrial injury.' " (Benson, supra, at p. 1552.) Accordingly, the appellate court concluded that "the Board properly made two awards of 31 percent permanent disability each, based on Dr. Izzo's opinion that the employee's permanent partial disability was equally caused by 'cumulative trauma through June 3, 2003,' and 'the specific injury of June 3, 2003.' " (Id. at p. 1560.)