My son 10mnths, has something sort of similar, he has tremors (head) and jerky movements, anyway I found this site (below)was a great help, you just type in your symtoms and it somes up with things related. Try the advanced search option, and in the bottom section of it, make sure that you pick the bottom dot only otherwsie you end up with thousands of therapy related and drug related things! Good luck (I think in my searching I found something that described your childs symptoms) I cant recall what it was called though. Cindy http://www.nlm.nih.gov/medlineplus/
Joshua (5) - autism, anaphylaxis, asthma, excema, mutiple severe allergies, tachycardia/palpitations. Kayne (3)- Aspergers, epilepsy, cyclic vomiting syndrome, autonomic disfunction. Corbyn (22mnths)- ataxia, hypotonia, tremor, blepharospasms, tic disorder, clonic movements, chewing/gagging issues.