20 C.F.R. § 220.185
After the Board finds that the annuitant is disabled, the Board must evaluate the annuitant's impairment(s) from time to time to determine if the annuitant is still eligible for disability cash benefits. The Board calls this evaluation a continuing disability review. The Board may begin a continuing disability review for any number of reasons including the annuitant's failure to follow the provisions of the Railroad Retirement Act or these regulations. When the Board begins such a review, the Board will notify the annuitant that the Board is reviewing the annuitant's eligibility for disability benefits, why the Board is reviewing the annuitant's eligibility, that in medical reviews the medical improvement review standard will apply, that the Board's review could result in the termination of the annuitant's benefits, and that the annuitant has the right to submit medical and other evidence for the Board's consideration during the continuing disability review. In doing a medical review the Board will develop a complete medical history of at least the preceding 12 months in any case in which a determination is made that the annuitant is no longer under a disability. If this review shows that the Board should stop payment of cash benefits, the Board will notify the annuitant in writing and give the annuitant an opportunity to appeal. In § 220.186 the Board describes those events that may prompt it to review whether the annuitant continues to be disabled.
20 C.F.R. §220.185