This is a chronic facial pain that does not correspond toa typical neuronerve innervation zonesor diagnostic criteria for pain syndromes, has no clear structural cause. The pain is usually constant, aching, or burning; it may change location or spread to an increasingly larger area of the face. This diagnosis is made by process of elimination once other causes of facial pain—trigeminal neuralgia, dental pathology, sinusitis, and temporomandibular joint dysfunction —are ruled out.