Dans,
Firstly - I am so sorry for the worry and concern and fear and frustration you must be feeling in relation to your son. If it were my son, I would not rule out lyme, if he had tick bites. Blood tests are not reliable, at all. Lyme is a clinical diagnosis. With regards to band 41 - I like this link for explaining it.
lymemd.blogspot.com/2008/09/all-i-got-was-41band.htmlI agree with Girlie, find a pediatric that is lyme literate and knows PANDAS.
I like this screening tool. Perhaps you could fill it out for your son. It was developed by a man that has treated thousands of lyme patients. His book, also, I found a worthy investment in that he has a schematic that considers all possibilities given symptoms.
www.tiredoflyme.com/horowitz-lyme-msids-questionnaire.html