Degenerative Myelopathy

Does anyone know anything about this disease?  It looks like my 11 yr old German Shepherd has developed this - a disease which is untreatable and will progessively attack the back legs, leading to paralysis and incontinence - so the vet tells me.  On top of that the same dog attacked my male GSD last night, very nearly blinding him.  This is the second time in 3 months that she's drawn blood. Just trying to get as many "health" facts as I can to help me make a decision which may be heartbreaking.  Hoping I can do something to prevent that which seems almost inevitable.............