Atypical or idiopathic facial pain (IFP) is a constant chronic orofacial discomfort or pain, which is defined by the International Headache Society as ‘facial pain not fulfilling other criteria’. Therefore, it is a diagnosis that can be difficult to make since it is reached only by the exclusion of organic disease. The organic disease that might cause similar chronic orofacial pain is typically in the local region but may be anywhere in the head and neck, or even in the chest; hence the difficulty in making this diagnosis safely.
IFP falls into the category of medically unexplained symptoms (MUS), most of which appear to have a psychogenic basis. It must be recognized, however, that a patient in pain may well also manifest psychological reactions to the experience.
The mouth and para-oral tissues have among the richest sensory innervation in the body. Furthermore, a large part of the sensory homunculus on the cerebral cortex receives information from orofacial structures. Right from infancy the mouth is concerned intimately with the psychological development of the individual, and disorders of structures such as the lips, teeth and oral mucosa can hold enormous emotional significance. It is hardly surprising, therefore, that orofacial disorders can result in considerable stress and that there are a range of psychogenic types of orofacial pain, including IFP.
Most sufferers from IFP are otherwise normal individuals who are, or have been, under extreme stress, such as bereavement or concern about cancer or an infection. Positron emission tomography in persons with IFP shows enhanced cerebral activity, suggesting an enhanced alerting mechanism in response to peripheral stimuli. This may lead to the release of neuropeptides and the production of free radicals, causing cell damage and the release of pain-inducing eicosanoids, such as prostaglandins. There may be a neuromuscular component.
The location of the pain is mainly in the upper jaw, unrelated to the anatomical distribution of trigeminal nerve innervation, poorly localized, and sometimes crosses the midline to involve the other side, or moves to another site.
The chronic pain may lead the patients to seek dental intervention, but to little avail. Patients may seek conservative dentistry, but this is rarely helpful – often rather to the contrary. The saga of pain may lead the clinician eventually to undertake endodontics or exodontics.
There is a high level of utilization of healthcare services: there have often already been multiple consultations and unsuccessful attempts at treatment. Many sufferers persist in blaming organic diseases (or the clinician!) for their pain.