Paraneoplastic or autoimmune disorders of the central nervous system, brain or spinal cord

**Definition:** Paraneoplastic and autoimmune disorders of the central nervous system, brain and spinal cord nervous system result from a targeted immune attack on neurons or glial cells in the central (e.g. encephalopathy, ataxia, myelopathy, myelitis) nervous system. In the paraneoplastic context, this attack is a consequence of a potentially effective tumour immune response initiated by onco-neural antigens derived from a systemic cancer. In the non-paraneoplastic context termed ‘autoimmune’ the etiology remains elusive though increasing evidence indicates a preceding infectious trigger in at least some cases. These disorders are commonly multifocal causing injury and symptoms arising from involvement at many levels of the central nervous system. A personal or family history of autoimmunity is often found. Accompanying neural and non-organ specific (thyroid peroxidase [TPO] antibodies) autoantibodies may be found. The neural autoantibody profile may be predictive of a specific cancer type and may be associated with a particular neurological phenotype. Exclusion of alternative etiologies (e.g. infections) is important. Response to immunotherapy may support the diagnosis.