The goal of treatment of OMS is early and aggressive immunotherapy with the goal of gaining a durable complete neurological remission. If a tumor is present, surgical resection is standard. The tumors in young children are usually low stage neuroblastomas or ganglioneuroblastomas (stage I or II), and tumor chemotherapy or radiation therapy are not generally indicated. Tumor resection does not usually provide sufficient clinical benefit for OMS, however.
OMS treatment, which is usually continued over at least 1-2 years, should involve combined immunotherapies as soon as possible after diagnosis. A three-agent protocol involving initial use of high-dose ACTH (corticotropin), IVIg, and rituximab has the best-documented outcomes for moderately severe and severe cases. Rituximab is a monoclonal antibody against B cells (anti-CD20). Almost all patients (80-90%) show improvement with this treatment, but maintaining sustained improvement may require additional treatment and very gradual weaning. Over time, treatment with ACTH may have substantial cortisol-related adverse effects that must be monitored carefully, particularly weight gain, hypertension, and reductions in bone density. Monthly pulse dose dexamethasone instead of ACTH is an option in mild and more moderate cases. The use of prednisone-type oral steroids is not recommended, because they are the least effective of the steroids for pediatric OMS. For OMS relapse, low-dose IV cyclophosphamide (3-6 cycles) or repeated courses of rituximab (1-2 cycles) are given. Oral weekly methotrexate may be a useful steroid sparer in chronic relapse.