Diagnosis and management of paraneoplastic neurologic disorders

Paraneoplastic neurologic disorders (PND) are a heterogeneous group of immune-mediated neurological disorders associated with systemic cancers. When a PND is diagnosed, prompt identification and treatment of the associated tumor is important as PND stabilization and in some cases improvement have been reported after tumor treatment. The cancer, however, may be small and difficult to detect or the onset of the PND may precede the development of the cancer by months or years. In the latter cases, patients often initially present to neurologists or internists who will need assistance from their oncology colleagues to uncover the cancer. It is therefore important to be aware of the associations of common cancers with specific PND syndromes and the significance in some PND of the presence in serum and/or cerebrospinal fluid (CSF) of specific antineuronal antibodies. Together, this information can focus the search for the tumor or support continued vigilance. Previously thought to be poorly responsive to therapies, it is now recognized that there is a subgroup of PND, mostly associated with antibodies to antigens on the neuronal cell surface that are highly treatment responsive. Treatments aimed at the PND are mostly immunosuppressive and include corticosteroids, plasma exchange and intravenous immunoglobulins (IVIg). Immunosuppressive chemotherapeutics and B-cell targeting drugs such as rituximab also may be useful. Although cancer patients tolerate these therapies, there is the risk of increased toxicity when combined with tumor-directed treatments and treatment plans should be coordinated between specialists.