Paraneoplastic neurologic disorders

Abstract

IntroductionParaneoplastic neurologic syndromes (PNS) are manifestations of cancers which are located outside the central nervous system. They appear before the diagnosis of cancer in most of patients. Identification of these disorders is very important as it leads to diagnosis and treatment of cancer subsequently. PNS are divided into two groups as classical and non-classical. Classical PNS are associated with cancer more than non-classical PNS. Non-classical PNS are rather observed in cases without cancer. PNS can also be divided into two groups as per the involvement of the central and peripheral nervous system (Table 1) (Bradley, 2008;Tüzün, 2010). EpidemiologyPNS are rare disorders in cancer patients. Frequency in all cancer patients is 0.01% (Darnell and Posner, 2003). Women/ men ratio is approximately 3:1. It is usually observed beyond mid-life. They show a closer association with some kinds of cancer. They have a more frequent association especially with hematologic diseases such as small cell lung cancer (SCLC), thymoma, and monoclonal gammopathy. Other can-cer types associated with PNS include breast, gynecological cancers such as ovarian and Hodgkin's, non-Hodgkin's lymphoma, testicular cancer and neuroblastoma (Toothaker and Rubin, 2009). Furthermore, development of PNS is possible in almost all neoplasms (Bataller and Dalmau, 2003). PathogenesisA widely accepted opinion is that these disorders occur due to stimulation of immune response by some proteins which are formed by a tumor, against both the tumor and the nervous system (Tüzün, 2010). Cytotoxic T-cell responses have a very important role in pathogenesis of PNS (Bradley, 2008). T-cells are responsible for both of the antibody-mediated processes (Albert et al., 1998). Lymphocytic pleocytosis and oligoclonal band positivity may be observed in BOS analysis (Armstrong et al., 2005).PNS are formed by antibodies developed against the intracellular antigen or neuronal surface antigen. In limbic encephalitis, there are antibodies for both regions. Anti Hu, anti Yo, anti Ri, anti Ma2, Cv2/CRMP5 are antibodies associated with intracellular antigen, whereas the VGKC complex