Board Thread:Theories and Speculation/@comment-35023081-20190916124836/@comment-1210805-20190916130654

Itachi was shown to be able to use the Susanoo without having his Mangekyo activated. The suggestion seems to be that it requires the Mangekyo to awaken the ability but not to use it. I'd also note that while the abilities of the Mangekyo are shown to do damage to the eyes, the Susanoo seemed to cause Sasuke pain throughout his entire body, further evidence that the Susanoo is more than a power of the eyes.