welcome to hcm
hv u taken out an Xray cervical spine?
if not go in for that AP and lateral view.
u could be suffreing from cervical spondylysis
the twitching is because of this only, the nerve
is getting compressed between the cervical vertebrae
and hence twitching.
in some cases giddiness is also present
try out physiotherapy
after proper diagnosis
do hot water fomentation to the neck
physio modality like traction is likely to give relief to arm twitching
ask your physio to show you neck isometrics
this will definitely help you