What are some early signs of turrets syndrome?

Ok so my son has this thing he does with his eyes where he blinks repeatedly and sometimes really hard. I know everybody blinks but this is way more frequent and different and and he doesn't stop for awhile once he starts. I thought it maybe his vision but he seems to see fine and he does this habit in any light or situation. I don't make a big deal of it. I don't want anyone to tease him.I didn't really think anyone noticed but me until someone pointed it out and asked me why he does that. Also if turrets is neurological then would they be able to tell for sure with a brain scan or something? I really haven't noticed anything else but the babysitter says he jerks his head but i think i would have noticed. Are there any other signs i should look for or am i worrying for nothing? He is 2 1/2.