Why is my snake twisting his head sideways?

We've had our milk snake for over 3 years now and as he has gotten older he is showing some skeletal/possible neurological abnormalities. He has a kink midway down his body that is not painful to the touch, but visible. It is like a flat spot but this snake has never had any injuries! And now his head is tilted sideways and when he stretches up the enclosure wall we can see that his whole body is twisted in that direction. He can grab his food (thawed small mice) but it's starting to affect his striking accuracy as he cannot make a straight strike. These seem to be getting worse slowly over time. Does anyone know of maybe a bone or muscle disease or congenital defect that would cause these? He eats fine otherwise and acts and appears healthy. Thanks, guys.