During the past 20 to 30 years, disorders of the nervous system, previously of unknown origin, associated with antibodies to self-antigens have been increasing. Some of these antigens are components of the cell surface, including components of synapses, such as ion channels and receptors for neurotransmitters.1 Other antibodies target antigens within the cytoplasm or nucleus.1,2 Most of these syndromes can be idiopathic or associated with the immune response, perhaps antigenically driven by neoplasms, and often have not been previously diagnosed. This finding should not be a surprise because 2 of the prototypic autoimmune neurologic diseases, myasthenia gravis and Lambert-Eaton myasthenic syndrome, can occur with or without accompanying neoplasms, such as thymoma in the case of myasthenia gravis and most often small cell carcinomas with Lambert-Eaton myasthenic syndrome. In case of some tumors, such as thymoma and small cell carcinoma, other neurologic paraneoplastic disorders can occur with other autoantibodies, such as Morvan disease with thymoma3,4 and several syndromes with small cell carcinoma, including sensory neuronopathy, necrotizing myelitis, and limbic encephalitis.5,6