help - diagnosis required PAIN++ neck and shoulder

hi all,
i have a pt with a 5 week hx of significantly limiting right shoulder and neck pain. unable to sit up in bed in morning from pain, but lessens during the day. CSp movements about 20% all directions, C1/2 movements worse and most tender on palp. pain in neck, traps, delt, teres minor
shoulder pain, joint passive ROM fine, but unable to move actively due to pain. loss of sensation C5/6 and worse on radial nerve. radial nerve stress test positive, tender along radial nerve on forearm with reproduction of hand symptoms (numbness and pain).
i went to give him Gr1/2 manual traction supine lying in neutral and he immediately got dizziness and black visual spots.
USS shows nothing incl vascular, Xray nothing, no sign of infection on blood test.
no hx trauma, woke with stiff neck, got a massage which helped initially then worsening of symptoms over next 24hours. went for a scuba dive the day previous.
i have no access to CT/MRI. he is admitted to hosp with pethidine injections which has minimised pain and improved his ROM.i am stuck and concerned.
any suggestions???

This may be due to psychological stress.. what about muscle tone? spasm usually.. no other diagnosis left as you done..