Atypical facial pain: clinical considerations and differential diagnosis.

Atypical facial pain (ATFP), recently defined as persistent idiopathic facial pain by the revision of the Classification of the International Headache Society (IHS), is a poorly understood condition, which still lacks clear diagnostic criteria and proper treatment. The pain is described as "persistent facial pain that does not have the characteristics of cranial neuralgias and is not attributable to another disorder". In general, however, according to the IHS criteria, a diagnosis of ATFP is possible when the pain in the face is present daily and persists for most or all of the day. The pain is confined at onset to a limited area on one side of the face, often in the nasolabial fold or side of the chin and may spread to the upper or lower jaw or a wider area of the face of neck and is deep and poorly localised. It is not associated with sensory loss or other physical signs. Laboratory investigations including X-ray of face and jaws do not demonstrate relevant abnormality. Pain may be initiated by operation or injury to face, teeth or gums but persists without any demonstrable local cause. But, the definition and the diagnostic criteria are over-simplified when we face the reality of the clinical practice. Many different disorders may be included in this diagnostic category, making differential diagnosis very complex. Diagnosis of ATFP is therefore, usually, a process of elimination. A targeted history and an accurate examination are crucial to correctly classify this facial pain.