Paraneoplastic syndromes causing movement disorders.

Paraneoplastic neurological disorders are an extensive group of neurological syndromes that occur in patients with cancer and often present before the presence of an underlying tumor is known. Many of these disorders appear to be immune-mediated, with targets throughout the nervous system, including basal ganglia and brainstem, in which case they may result in movement disorders. Recent descriptions of new immune-mediated encephalitides in children and adults have substantially increased the number of patients with paraneoplastic movement disorders. There are several key concepts that assist in the identification of a movement disorder as likely paraneoplastic, including a rapid onset, the presence of cerebrospinal fluid inflammatory changes, and in some patients the identification of specific serum and cerebrospinal fluid antineuronal antibodies. Once identified, prompt diagnosis and treatment of the tumor can result in neurological symptom improvement or stabilization, although some patients may require immunotherapy only. Understanding the natural course of each immune-mediated paraneoplastic movement disorder minimizes unnecessary testing and the use of potentially toxic therapies.