Paraneoplastic neurological syndromes (PNS) were initially defined as neurological syndromes of unknown cause that often antedate the diagnosis of an underlying, usually not clinically evident, cancer. In the last two decades, the discovery that many PNS are associated with antibodies against neural antigens expressed by the tumour (onconeural antibodies), has suggested that some PNS are immune mediated. PNS are rare and occur in less than 1% of patients with cancer. However, the diagnosis and treatment is important because the disability caused by the PNS is often severe and the correct diagnosis usually leads to the discovery of a small tumor with a high chance of being cured.
In November, 2002, a European Panel of neurologists interested in the field of PNS established the PNS Euronetwork supported by a European Union grant. The aim is to assist neurologists in the diagnosis and classification of PNS by providing rigorous diagnostic criteria for the different PNS, to interchange information among the different centres, and to facilitate the pooling of patients for clinical trials.