It depends on how long "it" has been going on ( a strep infection can go undetected for quite a long time). The first thing that has to be dealt with is killing off the strep ( antibiotics) and hoping that will do it.
There there is the inflammation of the brain ( sure, this is all controversial and PANDAS cannot be tested for via a "test" but if you have lived with it in your family, you know it exists). For some the inflammation goes down , naturally, once the strep is removed. If not, there are options like steroids ( awful experience for my child). If need be, IVIG or PEX can be done but they can be very, very expensive if your insurance co. does not agree that it is necessary.
For our child a tonsillectomy/adenoidectomy and a year long course of( twice a week) antibiotics seemed to work. Slowly. And we still have flare ups when exposed to strep or any viral infection. However, we are much more aware and have an amazing pediatrician and neurologist . Biggest suggestion when dealing with PANDAS, have every single family member ( including pets) tested for strep. You have to start with eliminating that, first.