The PainDETECT questionnaire (PD-Q), originally developed and validated in a multicentre study of neuropathic pain (NeP) patients with back pain, is increasingly being applied to other pain conditions. The present study assessed whether the PD-Q would be a suitable screening tool for detecting NeP in patients with post-traumatic inferior alveolar nerve injury (IANI) and lingual nerve injury (LNI). A prospective cohort of patients with clinically diagnosed neuropathy was given the PD-Q at their clinic appointment, or it was sent to them after their consultation. Eighty-nine patients (IANI = 56, LNI = 33) were included in the study, 75 of whom suffered from painful neuropathy. Of the patients who completed the questionnaire fully ( n = 56), allowing a summary score to be calculated, 34% were classified as having ‘likely NeP’ according to the PD-Q; 41% of patients scored in the uncertain classification range and the remaining quarter in the ‘likely nociceptive’ classification. There was a significant association between PD-Q scores and pain intensity levels across the sample, with those classified as likely NeP reporting high levels of pain. The results suggest that the PD-Q in its current format is not a suitable screening tool for NeP associated with IANI or LNI.
Chronic pain (pain of more than 3-month duration) can be a lasting problem for patients with iatrogenic inferior alveolar nerve injury (IANI) or lingual nerve injury (LNI). The most common causes of these injuries include third molar surgery, routine exodontia, complications of root canal treatment, and the placement of dental implants. A large proportion of these patients’ injuries give rise to symptoms with a neuropathic component, as indicated by complaints of burning pain, allodynia, tingling, and/or paraesthesia that are uncontrollable by non-steroidal anti-inflammatory drugs. These symptoms are debilitating and have substantial repercussions, such as the emotional impact of pain and long-term sensory deficits, which may directly affect the individual’s coping mechanisms and responses to stress, distress, anxiety, depression, treatment expectations, and motivation to improve.
Still a matter of debate, the International Association for the Study of Pain (IASP) defines neuropathic pain (NeP) as ‘pain initiated or caused by a primary lesion or dysfunction in the nervous system’. While increasing evidence supports abnormal central pain processing in chronic cases, the diagnosis of NeP remains clinical, based on a characteristic symptom profile (e.g., pins and needles, electric shock-like sensations), somatosensory abnormalities (e.g., hyperalgesia, hypoesthesia, allodynia), and, sometimes, ancillary tests. The PainDETECT questionnaire (PD-Q) screening tool was developed with a view to simplifying the diagnosis of NeP for clinicians, namely because it does not require a clinical examination. It was originally developed and validated in German, in a multicentre study of chronic low back pain patients, and appears to be a reliable screening tool in this diagnostic group: it has a sensitivity of 85%, specificity of 80%, and positive predictive value of 83%. The PD-Q has subsequently been translated into 22 languages, with various forms of delivery (for a review, see Bennett et al. ), and has been applied in studies of sensory profiles of various patient populations, including those with established neuropathic pain conditions, patients reporting widespread chronic musculoskeletal pain, patients suffering from osteoarthritis, and patients with post-surgical pain.
In orofacial pain conditions, the diagnosis of NeP remains challenging, predominantly because of the absence of associated clinical and radiographic abnormalities. Although confirmation of NeP in orofacial pain conditions can be made with some existing neurological tests, these tests have reduced accuracy in identifying subtle neuronal abnormalities and tend to be costly. Further, quantitative sensory testing (QST), which depends on expensive equipment and is time-consuming, is not always helpful in the differential diagnosis; and QST abnormalities cannot be taken as a conclusive demonstration of neuropathic pain. Thus, there is a significant need in this clinical population for efficient screening methods or tools providing a systematic approach to assessing NeP. A simple questionnaire-based measure, such as the PD-Q, has the potential to alleviate some of the financial burden and impact of persistent pain by early identification in neuropathic conditions, and thus may facilitate more timely administration of appropriate therapy.
In line with the further development of effective screening tools that can be utilized easily in the clinical arena in an accurate and cost-effective manner, the rationale for this study was to explore for the first time, whether or not the PD-Q is a useful tool for identifying NeP elements in two different known nerve injuries of the orofacial region.
Materials and methods
This was an observational clinical study assessing the suitability of using the PD-Q to screen for neuropathic pain components amongst patients with iatrogenic nerve injury.
A prospective cohort of patients with clinically diagnosed neuropathy was given the PD-Q at their clinic appointment, or it was sent to them after their consultation. Patients were included in the study if they presented to the clinic with reported sensory changes due to iatrogenic IANI or LNI, and could read and write in English sufficiently well to complete the questionnaire. The clinical diagnosis of neuropathic pain was ascertained by obtaining a pain history from each patient and confirming allodynia, hyperalgesia, or spontaneous neuropathic pain using several clinical neurosensory tests, as well as by recording the fact that their pain was unresponsive to non-steroidal anti-inflammatory drugs. The pain was recorded within a proven area of focal neuropathy corresponding to the trigeminal nerve branch damaged by the surgical intervention. Prior to completing the PD-Q, all patients underwent a trigeminal nerve examination carried out by the principal investigator (which included a series of neurosensory tests ), whereby trigeminal nerve injury was confirmed and neuropathy was diagnosed. Patients were excluded if they had chronic orofacial pain caused by other conditions. This study had the required ethical approval.
The PainDETECT questionnaire (PD-Q)
The PD-Q includes three 11-point numerical rating scales (NRS) dedicated to the evaluation of a patient’s reported current pain level and its strongest and average levels during the past month. The PD-Q also contains nine other items, of which seven relate to sensory responses and two to the temporal and spatial characteristics of the pain pattern. By rating the seven items from never (0) to very strongly (5) on a category scale and summing these with the scores for temporal (−1 to +1) and spatial characteristics (0 or +2), a summary score (minimum −1, maximum 38) was obtained. A total score of <13 indicates that a neuropathic component is unlikely, whereas a score of >18 indicates that a neuropathic component is likely. The online version of the questionnaire is available at: www.virtualmedicalcentre.com/calc_pfizer_pain_detect.asp .
Summary statistics for the overall sample and for the IANI and LNI patient subgroups were calculated and presented in the form of means and standard deviations for quantitative variables, and frequencies and percentages for qualitative variables. Differences between the two diagnostic subgroups on pain-related and PD-Q indicators were measured using one-way analysis of variance (ANOVA) or non-parametric equivalent for quantitative variables (according to data distribution) and χ 2 for qualitative variables. Associations between PD-Q NeP classifications and measures of pain intensity (current, 4-week strongest, and 4-week average strength) were evaluated considering the whole sample by one-way ANOVA models with post hoc (pairwise) examinations for significant results. To assess for correlations between the total PD-Q score and 4-week average pain intensity in each of the IANI and LNI groups, Spearman’s rank-coefficient tests were used. The criterion for statistical significance was set at P < 0.05, with no adjustments for multiple comparisons given the descriptive nature of the study. All statistical analyses were completed with IBM SPSS Statistics for Windows, version 19.0 (IBM Corp., Armonk, NY).
Altogether, 91 patients completed the PD-Q, 16 at their clinic appointment and 75 via questionnaires posted to them after their consultation. Two questionnaires were completed anonymously, so these patients’ data could not be included in the analyses. Eighty-nine iatrogenic nerve injury patients were therefore included in the study, 56 with IANI and 33 with LNI. Most patients were female (68.5%). The mean ± standard deviation (SD) age of participants was 44.26 ± 13.57 years (range 24–85 years), although IANI patients tended to be older than LNI patients (IANI 47.02 ± 13.64 years; LNI = 39.58 ± 12.26 years; t (87) = 2.58, P = 0.012). The mean duration of nerve injury was 18.50 ± 28.50 months (range 1–216 months), with the majority sustaining their injury more than 6 months prior to the study commencing ( n = 54 or 60.7%; IANI = 35 and LNI = 19). A little more than half of all patients’ nerve injuries were sustained during third molar surgery (TMS; 51.7%), although this was more likely for the LNI than IANI patients (81.8% and 33.9%, respectively; P < 0.001), with IANI arising from a wider range of procedures ( Table 1 ).