Personally, there was mystery for a long time, but rather than trying to solve the mystery fully, I tried to be pragmatic and do what helped.

I found that my range of motion turning my head one way was less than the other, having become restricted physically and psychologically, in a feedback loop.

I eventually went to a dentist who specialises in fascial pain who put me on muscle relaxants. These helped a little, but did not solve my issues. However they were a clue that some of my symptoms related to muscle tension. I was also experiencing increasing amounts of physical pain in my neck and face during this time.

Look into muscle shortening. It can be cumulative, as the pain caused by shortening causes the muscle to react more to strain, by shortening further.

I tried to compare my range of motion and both sides, and gradually try to match them through gentle stretching.

You could look into these things, and also trigger points. I can't say that my exact set of issues will be the same as yours, but feel free to contact me on Twitter if you want to chat. @paulbyrne

Quite often the ringing is worse after a day of sitting at work and typically reaches a veritable crescendo by Friday afternoon.

Likewise the onset of my tinnitus correlates with a period of stress and long hours at work sitting down.