Almost all DRG codes changed their meaning 2-3 times. So to have the correct mapping we need use dates, but in this case old data will remain unmapped since the concepts corresponding to old meanings of these codes are non-standard.
123 - CIRC DISOR W AMI, EXPIRED - 10-1-1989 - 09-30-2007 Non Standard
123 - NEUROLOGICAL EYE DISORDERS - 10-1-2007 - 12-31-9999 Standard
The similar problem exists for HCPCS and it is discussed here HCPCS codes change their meaning over time
So please notify when the common solution is worked out for these problems.