Hockey Dad

Radiation fibrosis in the neck is extremely common. I also recommend getting a prescription for physical therapy for your neck. Being unable to move your neck without pain a full rotation is so common, my CCC nurses called it: Wooden Soldier Syndrome.
Please go through all you old blood tests to see if you even had a TSH or thyroid test. Unfortunately, most cancer doctors do not take a baseline TSH before treatment, instead they rely upon the lab ranges of normal to test afterward. Sadly this is medically incorrect IMO since the lab ranges are so large for normal. 0.3 to 4.5 as to be individually meaningless. You want to be what you were before. I have discussed this a lot and really need to add this to all my welcome posts instead of just some.
Not opening your mouth is called Trismus. Here is the full OCF web page info on that OCF trismus I still use my Therabyte 5 years out.
Charm