Till there is scientific evidences, this is just pure speculation. I think that after this KO, ROach will tell him to retire, base on life experience, he's damn well placed to know what he's talking about.
Still, disease or not, Manny lost a bit of what he used to be, that we like it or not. At this point, he should retire or make one last fight that he could possibly win to call it a day and leave the ring in style but he should defo retire asap. Glorious career, stellar records, one of the most charismatic and spectacular fighter of his era. Perfect time to ride the sunset.