What Causes Throbbing Pulsations On The Neck?

for the past 3 months i have been getting this pulsating on the lower left hand side of my neck.. comes and goes but is very visible. does not hurt but is very uncomfortable...i saw a neurologist ayear ago about twitching a night time and he said my body wants to sleep but other parts are not cooperating.. he prescribed me ibelieve it is called closapham or something like that. when i am not on it my body twitches horribly at night time. anyway, the vein thing seems to be getting worse..HELP!