OK. Saw a Myotherapist today and he found something that no one had identified in the last 12 months. On my right, the first and second rib are elevated. It would seem that this could be the cause of my shoulder spasms and sternum pain.
I haven't mentioned the sternum pain here as I thought it could be wear and tear from the constant shoulder jerking. I have mentioned it to my GP and also to my current Neurologist as it has been causing discomfort for the last 7-8 months, but they didn't think it was significant.
The Myotherapist worked on it today, but freely admitted that he wasn't qualified to realign them, so I'm going to see my Chiropractor on Friday to see if she can put them back in place.