Evaluation of Neuropathic Pain Diagnostic Criteria Applied to Orofacial Pains

Introduction: Diagnostic criteria for neuropathic pain have recently been proposed (Kehlet et al, Lancet, 2006). Several orofacial pain conditions such as idiopathic trigeminal neuralgia, symptomatic trigeminal neuralgia (from MS or tumors), and trigeminal nerve injury pain, are generally assumed to be neuropathic in mechanism. Before these criteria can be used for other orofacial pains, the question arises: How well do these criteria perform for well-known neuropathic orofacial pains? Methods: In conjunction with an international taskforce, a systematic review of studies of chronic orofacial pain conditions that are generally accepted as neuropathic and utilized neurosensory testing was performed. General neuropathic pain criteria by Kehlet were applied to trigeminal pain: 1) pain localized to neuroanatomical region; 2) relevant disease/pathology of the nervous system; 3) partial/complete sensory loss in all/ part of painful site; 4) confirmation with surgery, imaging, neurophysiological tests or biopsy. Studies were located from multiple searches of bibliographic databases, experts in the field, and reference lists from articles. Study inclusion criteria were: original research, neurosensory tests performed on live humans with trigeminal based pain lasting more than 3 months. The proportion of subjects meeting specific criteria for trigeminal neuropathic pain was abstracted, and the mean percentage meeting each criterion was calculated. Results: 25 eligible studies were located. Of articles that met inclusion criteria, less than 10% of subjects met all four criteria. The mean percentage of subjects that met each neuropathic pain criterion for the 3 following conditions are listed: trigeminal nerve injury (TNI), symptomatic trigeminal neuralgia (STN) and idiopathic TN (ITN)1:localized pain, 69,100;100; 2:relevant disease, 100,97,0; 3:sensory loss, 31,10,0; 4:confirmatory tests, 81,93,30-50. Conclusions: The orofacial pain conditions studied, which are generally regarded to be neuropathic in mechanism, do not meet all four proposed criteria for neuropathic pain. Modifications to, and operationalized criteria for neuropathic pain are suggested. Support: K12-14079/T32-RR023256.