Clinical criteria for trigeminal neuralgia

Abstract

The report by Sato et al1.Sato J Saitoh T Notani K Fukuda H Kaneyama K Segami N Diagnostic significance of carbamazepine and trigger zones in trigeminal neuralgia.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004; 97: 18-22Google Scholar (“Diagnostic significance of carbamazepine and trigger zones in trigeminal neuralgia”) contains multiple basic errors in methodology, data collection, and interpretation that make it difficult to draw any meaningful conclusion from the study. This is unfortunate, since the report raises an important issue: there are few scientific studies that validate the current clinical criteria for trigeminal neuralgia (TN). A number of headache and facial pain disorders are diagnosed by specific criteria based on patient signs and symptoms. These criteria are particularly important for disorders such as TN and migraine, where diagnostic tests and physical exam findings are frequently unremarkable. Symptom-based diagnostic criteria represent a major advance for both research and clinical care. Of course, this is nothing new. Diagnostic criteria for TN have been available for at least half a century2.White J.C Sweet W.H Pain: Its mechanisms and neurosurgical control. Charles Thomas, Springfield, Ill1955Google Scholar and, arguably, much longer.3.Stookey B Ransohoff J Trigeminal neuralgia: Its history and treatment. Charles Thomas, Springfield, Ill1959Google Scholar Within the last few decades, diagnostic criteria for TN were accepted by the International Association for the Study of Pain4.Merskey H Bogduk N Classification of chronic pain: Descriptions of chronic pain syndromes and definitions of pain terms. IASP Press, Seattle1994Google Scholar and the International Headache Society (IHS). Quite recently, IHS published the second edition of its consensus diagnostic criteria.5.Headache Classification Subcommittee of the IHS, The International Classification of Headache Disorders Second Edition.Cephalalgia. 2004; 24 (126-7)Google Scholar However, despite this history, there have been few research validation studies of the globally-accepted TN diagnostic criteria. We appreciate that validation studies are difficult in disorders that cannot be confirmed by objective testing. However, it is noteworthy that statistical validation approaches are widely used to assess diagnostic criteria in psychiatry. Similar validation methods have also been applied to the diagnostic criteria for migraine, with interesting results.6.Merikangas K.R Whitaker A.E Angst J Validation of diagnostic criteria for migraine in the Zurich longitudinal cohort study.Cephalalgia. 1993; 13: 47-53Google Scholar In our opinion, the rigorous analysis of TN diagnostic criteria is fundamentally important. We think such studies are long overdue. Regarding the report of Sato et al,1.Sato J Saitoh T Notani K Fukuda H Kaneyama K Segami N Diagnostic significance of carbamazepine and trigger zones in trigeminal neuralgia.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004; 97: 18-22Google Scholar we think the authors might agree that the correlation of precisely-defined “trigger zones” with other TN signs and symptoms should be an important part of any internal validation analysis of the diagnostic criteria. We also think they might agree that a therapeutic response to carbamazepine could be a factor addressed in future studies testing the external validation of TN criteria. Careful validation studies of the diagnostic criteria for facial pain disorders are essential for future progress in clinical care and research. We believe such studies must be pursued, not only for their scientific merit, but also for their important role in relief of clinical pain.