Differential diagnosis is based on the pain history in combination with the clinical findings of muscle spasm and occlusion in relation to the condylar displacement as observed in the TMJ radiographs. Most often TMJ dysfunction-pain syndrome produces symptoms that have a pattern of occurrence or can be associated with function. Neurologic, vascular, and conversion pain occur at random without a pattern of occurrence and with no relation to function. Atypical TMJ dysfunction pain can occur by itself or in combination with other unrelated pain causes. Differential diagnosis is usually aided by injections of local anesthetics and diagnostic trials of an anterior bite plate and relaxant drugs. Medical consultation is advised when a diagnosis of TMJ dysfunction-pain syndrome cannot be established. Hysterical conversion is extremely rare, although occasionally a patient may have pain of unknown origin.