My father 70 yrs. cabg 1999. hypertensive and dm -good control diffuse cerebellar and cerebral atrophy & microvascular ischemic disorder - treatment?

No cure: The changes you describe are typical ct changes of most people over age 60 with dm and htn. There's nothing that will reverse those changes. To slow progression which is as inexorable as aging, keep the BP and cholesterol under meticulous control. Control of dm is important for other reasons but may not slow the vasular changes. Of course, no smoking. Good diet and regular exercise also help.