Paraneoplastic Neurological Syndrome

Autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) are rare neuroimmune syndromes with a wide range of clinical presentation but without pathognomonic clinical sign facilitating the diagnosis. A lot of differential diagnoses are possible such as neurodegenerative diseases or viral infections. Although rare the diagnosis of AE or PNS is essential because despite severe neurological symptoms, patients can be cured by appropriate immunotherapy. Autoantibodies highly specific of AE and PNS has been described in the serum and cerebrospinal fluid of the patients and can be used as biomarkers of the disease. Their presence can predict an autoimmune origin and in many cases a good prognosis after immunotherapy. However, if some autoantibodies are now well-characterized and industrial kits have been developed to detect them, in numerous cases of highly suspect AE or PNS no specific autoantibodies are identified leading frequently to an inappropriate treatment. Furthermore, as the mechanisms of AE and PNS is still unknown, treatments are not optimal and in some cases inefficient. There is no prognosis biomarker able to predict the patient's sensitivity to immunotherapy and there are only few clues to know how the immune system can provoke the neuropsychiatric symptoms observed in the patients.