How do you decide when to discontinue immunotherapy for primary angiitis of the central nervous system (PACNS)?

I take a multidisciplinary approach with involvement of my neurobiology and rheumatology colleagues for the immunotherapy. PACNS can be relapsing or remitting. So needs close monitoring with radiologic (MRI and MRA high resolution vessel wall imaging or CTA/MRA with CSF studies 6 months and then 1 y...