I had neck surgery 5 months ago to repair a non union in my neck. A few weeks after I noticed when I would lay my head down I felt horrible pressure and I would have to life my head up immediately. It only happens when I lay flat and turn my head slightly to the left. I did a balance test, mri on my inner ear and lower brain. All tests came back normal. Went back to my orthopedic surgeuron and found nothing.