Paraneoplastic Neurological Syndromes (PNS) can be defined as remote effects of cancer that are not elicited by the tumor and its metastasis, or by infection such as ischemia or metabolic disruptions. They are caused by autoimmune processes triggered by the cancer and directed against antigens common to both the cancer and the nervous system: onconeural antigens. PNS are rare, affecting less than 1/10,000 cancer patients. Only Lambert-Eaton myasthenic syndrome is relatively frequent, occurring in approximately 1% of patients with small-cell lung cancer. PNS are usually severely disabling.