My 11 year old has many of these same symptoms. He tested positive for mycoplasma. His PANDAS doctor switched his prophylactic antibiotic to address it.
Here is further info about my son's journey for relief. By no means, do I recommend the same for your son. However, it may give you more information in solving the puzzle.
He was also diagnosed with OCD, General Anxiety Disorder, Social Phobia (school anxiety) outside of PANDAS. In other words, antibiotics weren't the only solution for him.
During his worst flare last year where he was hearing voices and had already tried multiple antibiotics, steroid bursts, ibuprofen bursts, the only thing that helped was Abilify. Similar to seeing sudden (days) relief with PANDAS symptoms when prescribed an antibiotic, the Abilify seemed to work with him. He was also prescribed Zoloft because having his symptoms long-terms had created a depression he was unable to get himself out of.
For a long time, I refused to give him SSRIs, antipsychotics, and benzodiazepines. I spent a year during this severe flare seeing doctor after doctor, trying to get an order for IVIG because that was my last resort. He got worse and worse. I saw several child psychiatrists, both experienced with treating PANDAS kids and not. The ones with the experience were full. They would do an evaluation but had so many PANDAS kids they couldn't see anymore.The psychiatrists with no PANDAS experience were pointless. They didn't believe in it and tried to put him in a box. PANDAS kids are difficult to treat. They are a complex puzzle and if a doctor doesn't believe that, it's pointless to see them.
When I found a PANDAS psychiatrist to take my son as a patient, he was at such a state that I was convinced to try these medications. They didn't alleviate all of his PANDAS-like symptoms but helped so much. His depression improved, he stopped hearing voices, and his rages were fewer and less intense. There were some days that he was happy.
A couple of months later I also took him to a PANDAS specialist in Florida who agreed with the course of treatment, but changed the antibiotic and added supplements. He also did an intensive CBT therapy. All of these things helped.
He still has flares. He is having one now (wetting the bed, dilated pupils, intense anxiety, anti-social behavior, school issues, etc). But, these medications actually help us to determine if he is having a PANDAS flare and needs to be tested. We are trying an ibuprofen burst as a first course of treatment before doing lab work and adding another antibiotic.
I do recommend that you find experienced PANDAS doctors. In addition to my son's PANDAS doctor who we see every 4 months, he sees a PANDAS-experienced neurologist when needed (sleep issues), a PANDAS-experienced pediatrician, a PANDAS-experienced psychiatrist, and a PANDAS-experienced psychologist for weekly CBT and Behavior Therapy.
All of these doctors told me the same thing. Regardless of a PANDAS diagnosis, the treatment approach is the same. Test results are not definitive because inflammation changes. All of the tests I insisted on helped, but were not the key decision makers for his doctors on treating him. His symptoms were.
I don't have any direct advice to give you. I can only tell you how we approached my son's last severe flare to give you more information. This forum was so important in helping me understand and help my doctors understand how to treat my son.
The right doctors are key to helping your son. All of the tests I insisted on helped, but were not the key decision makers for his doctors on treating him. His symptoms were.