Treatment of paraneoplastic neurologic disorders

Paraneoplastic neurologic disorders are rare, autoimmune disorders, which can be broken down into two groups: those in which antibody response is directed against intracellular neuronal or neuroglial proteins (Group 1) and those in which the immune response is directed against antigens within or subjacent to the neuronal cell membrane (Group 2). In both groups, detection and treatment of the underlying neoplasm is critical and carries the best chance of clinical stabilization or remission.Syndromes in Group 2 frequently respond to therapy. This may involve corticosteroids, plasma exchange (PE), or intravenous immunoglobulin G (IgG), depending on the specific paraneoplastic syndrome. Cyclophosphamide or rituximab may be helpful in patients who fail to stabilize or improve on less aggressive therapies.Treatment of syndromes in Group 1 is far more difficult, and proven treatment strategies do not exist. Younger men (< 40 years of age) with limbic or brainstem syndromes, testicular or germ cell tumors, and anti-Ma2 antibodies may respond to specific tumor treatment together with immunotherapy. Patients with paraneoplastic syndromes and anti-Ri antibodies may respond to corticosteroids and/or cyclophosphamide. Evidence-based treatment guidelines do not exist for patients with other central paraneoplastic syndromes such as cerebellar degeneration or encephalomyeloneuritis. Approaches to therapy, apart from treating the underlying tumor, are thus speculative.In patients with rapidly progressive symptoms classically suggestive of a paraneoplastic neurologic syndrome, time is of the essence in arresting neurologic deterioration. Clinical improvement in patients with longstanding symptoms is unlikely. At the outset, one should move rapidly to define the antibody response involved, as this may also assist tumor diagnosis. Treatment may include prednisone, intravenous IgG, and cyclophosphamide; rituximab plus prednisone may be an alternative, either initially or in the face of continued disease progression despite treatment with intravenous IgG or cyclophosphamide. Although PE is of questionable benefit, a single cycle of PE may be considered before other treatment, to achieve rapid lowering of circulating paraneoplastic autoantibodies.