Paraneoplastic neurological syndromes (PNS) are remote effects of malignant neoplasia on neural tissue, not directly caused by mass lesions, metastases, infections, ischemia, coagulopathy, metabolic disruptions or treatment. The symptoms and signs of PNS are diverse, usually acute or subacute. Onconeural antibodies are detected in their serum, and sometimes in their Cerebrospinal Fluid (CSF); onconeural antibodies are highly specific for identifying patients with neurologic symptoms as having a paraneoplastic syndrome. The most frequent ones are anti-Hu, anti-Yo and anti-CV2/CRMP5. Although a known cancer patient may present with a PNS, neurologic symptoms precede other manifestations of a tumor in about 65% of patients.