[Limbic encephalitis with antibodies against intracellular antigens].

Limbic encephalitis is a paraneoplastic syndrome that is often associated with small cell lung cancer (SCLC), breast cancer, testicular tumors, teratoma, Hodgkin's lymphoma and thymoma. The common clinical manifestations of limbic encephalitis are subacute onset, cognitive dysfunction, seizures and psychiatric symptoms. Paraneoplastic neurological disorders are considered to occur because of cytotoxic T cell responses and antibodies against target neuronal proteins that are usually expressed by an underlying tumor. The main intracellular antigens related to limbic encephalitis are Hu, Ma2, and less frequently CV2/CRMP5 and amphiphysin. The anti-Hu antibody, which is involved in cerebellar degeneration and extensive or multifocal encephalomyelitis such as limbic encephalitis is closely associated with a history of smoking and SCLC. The anti-Ma2 antibody is associated with encephalitis of the limbic system, hypothalamus and brain-stem. For this reason, some patients with limbic encephalitis have sleep disorders (including REM sleep abnormalities), severe hypokinesis and gaze palsy in addition to limbic dysfunction. In men aged less than 50 years, anti-Ma2 antibody encephalitis is almost always associated with testicular germ-cell tumors that are occasionally difficult to detect. In older men and women, the most common tumors are non-SCLC and breast cancer. Limbic encephalitis associated with cell-surface antigens (e.g., voltage-gated potassium channels, NMDA receptors) is mediated by antibodies and often improves after a reduction in the antibody titer and after tumor resection. Patients with antibodies against intracellular antigens, except for those with anti-Ma2 antibodies and testicular tumors, are less responsive. Early diagnosis and treatment with immunotherapy, tumor resection or both are important for improving or stabilizing the condition of limbic encephalitis.