Abstract
Dear Sir We read with interest the timely article published by Zebenholzer et al. (1). Their findings should alert us all to the need for further study regarding the diagnosis and classification of facial pain. Applying the most recent classification of the International Headache Society (IHS) (2) to the 97 patients studied they found that about 21% were diagnosed with persistent idiopathic facial pain and about 29% were unclassifiable. As a tertiary pain centre the patients such as those reported (1) are usually complex, whilst it is reasonable to assume that straightforward cases such as temporomandibular disorders (TMD) are commonly diagnosed and treated efficiently at primary care centres.
However, the finding that 50% of cases are essentially labelled as idiopathic or undiagnosable (1) according to IHS criteria is disturbing. In the 20–30 years that we have been involved in the care of chronic orofacial pain patients we have similar (3, 4) although largely unpublished observations. We have persistently applied the IHS classifications for both research and clinical activities but have found these insufficient in orofacial pain patients, particularly those with TMDs or with facial pain accompanied by atypical features. For example, clinical differences between tension-type headache (TTH) and regional masticatory muscle myofascial pain (MMP) justify separate classification. MMP is viewed by orofacial pain specialists as a primary facial pain (5), not secondary to temporomandibular joint disease (6, 7), and has been shown to be largely unrelated to muscle hyperactivity (8). Although MMP may share pathophysiological mechanisms with TTH, it seems to be a distinct entity justifying separate classification (7). In such cases we are forced to rely on alternative classifications that detail orofacial pain syndromes, most recently the classification published by the American Academy of Orofacial Pain (5), conveniently modelled on the IHS classification. Analysing the cases presented by Zebenholzer et al. (1), one could argue that in cases with pain beginning after surgery accompanied by sensory deficit, a diagnosis of post-traumatic neuropathic pain may reasonably be applied (5, 9). Similarly, a patient with long-lasting paroxysmal pain accompanied by autonomic signs could be suffering from vascular orofacial pain (3) or a trigeminal autonomic cephalgia (TAC) variant, i.e. probable TAC (2). However, the aim of this letter is not to criticize the diagnoses presented in this excellent publication, rather to utilize its findings as a platform to encourage the IHS to cooperate more extensively with orofacial pain specialties so as to expand its classification of orofacial pain syndromes. This will no doubt expand our abilities to diagnose such pain entities accurately and limit inconclusive diagnoses such as idiopathic persistent facial pain and atypical facial pain.