Yes, this is what Danger had. The left side of his head caved in, but since he was behaving normally, we chatted with our regular Vet and we took a wait-and-see stance on it. Several months later, he developed an eye issue and we took him to an Eye Vet who strongly recommended a Neurology exam. The Neurologist took one look at him and knew what it was. She said we could do an MRI or watch it. We did not do an MRI as there is no cure or real treatment and it would not alter the course of events for Danger. Plus we just could not afford it. We tried pred. for a while and saw no improvement.
Danger thrived for well over a year after the muscle cave in. He did have multiple eye issue with the same side eye that required constant treatment. We kept his eye lubricated with an OTC eye gel for people. The deficits started showing up, but he did fine for a while. The deficits starting worse and severe enough that he was having trouble walking and such. His eye finally blew up and we could not keep it in check. We knew he was at the end. Good luck.