[¶ 8] The pivotal dispute is whether Hibl's 1981 and 1984 work injuries substantially aggravated or accelerated progression of his spondylolisthesis. In order to receive benefits from the fund, a claimant has the burden of proving he has sustained a compensable injury. N.D.C.C. § 65-01-11; Symington v. North Dakota Workers Compensation Bureau, 545 N.W.2d 806, 808 (N.D. 1996); Wherry v. North Dakota State Hospital, 498 N.W.2d 136, 139 (N.D. 1993). At the time of Hibl's 1996 surgery, N.D.C.C. § 65-01-02(9)(b)(6) defined "compensable injury," to exclude: The definition of "compensable injury" has been amended and is now codified at N.D.C.C. § 65-01-02(11).

Spangler v. N.D. Workers Compensation Bureau, 519 N.W.2d 576, 577 (N.D. 1994). It is within the province of the Bureau to weigh the credibility of medical evidence. Symington v. N.D. Workers Compensation Bureau, 545 N.W.2d 806, 809 (N.D. 1996). Though the Bureau may resolve conflicts between medical opinions, the authority to reject medical evidence selectively does not permit the Bureau to "pick and choose in an unreasoned manner." Spangler, 519 N.W.2d at 577 (citing Weber v. N.D. Workmen's Compensation Bureau, 377 N.W.2d 571, 574 (N.D. 1985)).

Ohlson v. Dept. of Human Services, 552 N.W.2d 73, 75 (N.D. 1996). "To participate in the workers compensation fund, a claimant must prove a compensable injury by a preponderance of the evidence." Symington v. N.D. Workers Comp. Bureau, 545 N.W.2d 806, 808 (N.D. 1996); N.D.C.C. § 65-01-11. In reconciling the claimant's burden of proof with our standard of review, we require the Bureau to clarify the inconsistencies and adequately explain its reasons for disregarding medical evidence favorable to the worker.

We have previously declined to establish a presumption entitling a treating doctor's opinion to "great weight." Symington v. N.D. Workers Comp. Bureau, 545 N.W.2d 806, 809-10 (N.D. 1996) (declining to adopt rules which rank the weight of evidence offered by physicians of different specialities or of treating and examining physicians). The Bureau must examine and weigh the credibility of the medical evidence.Id. at 809 (citing Latraille v. N.D. Workers Comp. Bureau, 481 N.W.2d 446, 450 (N.D. 1992)).

"In considering whether the Bureau's findings of fact are supported by a preponderance of the evidence, we exercise restraint and do not make independent findings of fact or substitute our judgment for the Bureau's determination." Symington v. N.D. Workers Compensation Bureau, 545 N.W.2d 806, 808 (N.D. 1996). [¶ 27] Under N.D.C.C. § 28-32-19 (1991), the statutory authority in effect at the time of the Bureau's order:

[¶ 18] It is the Bureau's responsibility to weigh the credibility of medical evidence, but in resolving conflicts the Bureau must consider the entire record, clarify inconsistencies, and explain its reasons for disregarding medical evidence favorable to the claimant. Hibl v. North Dakota Workers Compensation Bureau, 1998 ND 198, ¶ 10, 586 N.W.2d 167; Geck v. North Dakota Workers Compensation Bureau, 1998 ND 158, ¶ 5, 583 N.W.2d 621; Symington v. North Dakota Workers Compensation Bureau, 545 N.W.2d 806, 808 (N.D. 1996). In Otto v. North Dakota Workers Compensation Bureau, 533 N.W.2d 703, 706 (N.D. 1995), this Court explained:

[¶ 25] This Court has declined to establish a presumption entitling a treating doctor's opinion to "great weight," but recognizes that a long-term doctor-patient relationship "may afford the treating doctor a more comprehensive view of the claimant's medical history and condition." Boger v. North Dakota Workers Comp. Bureau, 1999 ND 192, ¶ 16, 600 N.W.2d 877 (citing Symington v. North Dakota Workers Comp. Bureau, 545 N.W.2d 806, 809-10 (N.D. 1996)). [¶ 26] The Bureau distinguishes Dr. DeGree's opinion by noting his opinion, joined by Dr. Martire, is the only one that reasons a mild brain injury may have caused Siewert's symptoms.

See id. (quoting Feist v. North Dakota Workers Comp. Bureau, 1997 ND 177, ¶ 8, 569 N.W.2d 1). "`To participate in the workers compensation fund, a claimant must prove a compensable injury by a preponderance of the evidence.'" Lang v. North Dakota Workers Comp. Bureau, 1997 ND 133, ¶ 7, 566 N.W.2d 801 (quoting Symington v. North Dakota Workers Comp. Bureau, 545 N.W.2d 806, 808 (N.D. 1996)); see N.D.C.C. § 65-01-11. "In reconciling the claimant's burden of proof with our standard of review, we require the Bureau to clarify the inconsistencies and adequately explain its reasons for disregarding medical evidence favorable to the worker."

[¶ 16] Hoyem did not raise this distinction as an issue to the Bureau and to the district court within the framework of his argument that Appendix B applied to his claim for a pain evaluation and rating. We have often said issues not raised before an administrative agency will not be considered for the first time on appeal. E.g. Symington v. North Dakota Workers Comp. Bur., 545 N.W.2d 806, 810 (N.D. 1996). We therefore decline to address Hoyem's argument about acute recurrent pain.

We thus decline to address this issue. See, e.g., Symington v. North Dakota Workers Compensation Bureau, 545 N.W.2d 806, 810 (N.D. 1996). V