Lene Baad-Hansen

Reliability of intraoral quantitative sensory testing (QST)

&NA; The German Research Network on Neuropathic Pain (DFNS) has recommended a protocol with 13 quantitative sensory testing (QST) measures for detecting somatosensory abnormalities. Reliability is an important scientific property and has been adequately tested for cutaneous QST. This study evaluates intraoral sites for which no reliability trials have yet been published. Inter‐ and intra‐examiner reliability of 13 QST measures at intra‐ and extraoral trigeminal sites were investigated. Twenty‐one healthy volunteers from Malmö University, Malmö, Sweden (13 women and 8 men, mean age 40.4 years, range 24–71) participated. Two independent examiners previously trained in the DFNS QST protocol examined the participants using the entire protocol. Each participant was examined twice on the same day, once by each examiner (inter‐examiner reliability). After 1–3 weeks, one examiner re‐examined all participants (intra‐examiner reliability). The measurements were made on the skin of the right cheek, the tip of the tongue, and bilaterally on the gingival mucosa of the upper premolar region. The intraclass correlation coefficient (ICC) or kappa was used to calculate variations. Most tests had acceptable to excellent inter‐examiner (ICC 0.41–0.89) and intra‐examiner (ICC 0.43–0.87) reliability. For each test, inter‐ and intra‐examiner reliabilities at intra‐ and extraoral sites were similar. No significant differences between right and left sides were found intraorally. We conclude that inter‐ and intra‐examiner reliabilities of most QST measures are acceptable for assessing somatosensory function in the orofacial region.

Relationships between craniofacial pain and bruxism.

A still commonly held view in the literature and clinical practice is that bruxism causes pain because of overloading of the musculoskeletal tissue and craniofacial pain, on the other hand, triggers more bruxism. Furthermore, it is often believed that there is a dose-response gradient so that more bruxism (intensity, duration) leads to more overloading and pain. Provided the existence of efficient techniques to treat bruxism, it would be straightforward in such a simple system to target bruxism as the cause of pain and hence treat the pain. Of course, human biological systems are much more complex and therefore, it is no surprise that the relationship between bruxism and pain is far from being simple or even linear. Indeed, there are unexpected relationships, which complicate the establishment of adequate explanatory models. Part of the reason is the complexity of the bruxism in itself, which presents significant challenges related to operationalized criteria and diagnostic tools and underlying pathophysiology issues, which have been dealt with in other reviews in this issue. However, another important reason is the multifaceted nature of craniofacial pain. This review will address our current understanding of classification issues, epidemiology and neurobiological mechanisms of craniofacial pain. Experimental models of bruxism may help to further the understanding of the relationship between craniofacial pain and bruxism in addition to insights from intervention studies. The review will enable clinicians to understand the reasons why simple cause-effect relationships between bruxism and craniofacial pain are inadequate and the current implications for management of craniofacial pain.

Guidelines and recommendations for assessment of somatosensory function in oro-facial pain conditions - a taskforce report

The goals of an international taskforce on somatosensory testing established by the Special Interest Group of Oro-facial Pain (SIG-OFP) under the International Association for the Study of Pain (IASP) were to (i) review the literature concerning assessment of somatosensory function in the oro-facial region in terms of techniques and test performance, (ii) provide guidelines for comprehensive and screening examination procedures, and (iii) give recommendations for future development of somatosensory testing specifically in the oro-facial region. Numerous qualitative and quantitative psychophysical techniques have been proposed and used in the description of oro-facial somatosensory function. The selection of technique includes time considerations because the most reliable and accurate methods require multiple repetitions of stimuli. Multiple-stimulus modalities (mechanical, thermal, electrical, chemical) have been applied to study oro-facial somatosensory function. A battery of different test stimuli is needed to obtain comprehensive information about the functional integrity of the various types of afferent nerve fibres. Based on the available literature, the German Neuropathic Pain Network test battery appears suitable for the study of somatosensory function within the oro-facial area as it is based on a wide variety of both qualitative and quantitative assessments of all cutaneous somatosensory modalities. Furthermore, these protocols have been thoroughly described and tested on multiple sites including the facial skin and intra-oral mucosa. Standardisation of both comprehensive and screening examination techniques is likely to improve the diagnostic accuracy and facilitate the understanding of neural mechanisms and somatosensory changes in different oro-facial pain conditions and may help to guide management.

Atypical odontalgia – pathophysiology and clinical management

Atypical odontalgia (AO) is a chronic form of dental pain without signs of pathology. Several hypotheses have been put forward regarding the pathophysiology. AO has been proposed to be psychogenic, vascular, neuropathic or idiopathic. The scientific evidence supporting or rejecting these hypotheses are reviewed in this paper. At this time, the best supported hypothesis is that AO is a neuropathic pain condition. Relevant differential diagnoses, such as odontogenic pain, sinusitis, trigeminal neuralgia among others, are presented and the evidence regarding possible management strategies is reviewed. A treatment algorithm for AO is proposed based on the rather scarce scientific evidence available and inspired by a similar treatment algorithm for peripheral neuropathic pain. The proposed strategy involves an interdisciplinary approach including patient education, psychological counselling, topical and systemic medication and, importantly, avoidance of invasive treatments like surgery and endodontics. Two illustrative cases are presented.

Lack of sex differences in modulation of experimental intraoral pain by diffuse noxious inhibitory controls (DNIC).

&NA; The aims of this study were to investigate possible sex differences in (a) intraoral pain evoked by topical application of capsaicin to the gingiva, and (b) the modulation of this pain by diffuse noxious inhibitory controls (DNIC). Three groups with a total of fifty‐four healthy volunteers (20 men, 20 women using oral contraceptives (W+OC), 14 women not using (W−OC)) completed the study. In two sessions, intraoral pain was evoked by topical application of 30 μL 5% capsaicin to the gingiva. Conditioning stimuli were applied with three min hand immersion in ice water in one session and 30 °C water (control) in another session. The capsaicin‐evoked pain and the water‐evoked pain were evaluated by the participants on visual analogue scales (VAS). No main effects of group in capsaicin‐evoked pain (P>0.062) or water‐evoked pain (P>0.149) were found. There was a significant group x time interaction (P<0.001) with W+OC reporting lower capsaicin‐evoked pain scores than W−OC in the early phase (2–3 min) and lower pain scores than men in the later phase (5–11 min). The degree of modulation by DNIC did not differ between groups (P=0.636). In conclusion, for a superficial type of intraoral pain, only minor sex differences were found in pain intensity and no differences in the degree of endogenous modulation by DNIC. Female sex and the use of OC may not consistently be associated with higher sensitivity to pain.

Hypnosis in the management of persistent idiopathic orofacial pain : Clinical and psychosocial findings

&NA; This controlled and patient blinded study tested the effect of hypnosis on persistent idiopathic orofacial pain (PIOP) in terms of clinical and psychosocial findings. Forty‐one PIOP were randomized to active hypnotic intervention or simple relaxation as control for five individual 1‐h sessions. Primary outcome was average pain intensity scored three times daily in a pain diary using visual analogue scale (VAS). Secondary outcome measures were pain quality assessed by McGill pain questionnaire (MPQ), psychological symptoms assessed by symptom check list (SCL), quality of life assessed by SF36, sleep quality, and consumption of analgesic. Data were compared between groups before and after treatment using ANOVA models and paired t‐tests. The change in VAS pain scores from baseline to the last treatment (t4) was (33.1 ± 7.4%) in the hypnosis group and (3.2 ± 5.4%) in the control group (P < 0.03). In the hypnosis group, highly hypnotic susceptible patients had greater decreases in VAS pain scores (55.0 ± 12.3%) when compared to less susceptible patients (17.9 ± 6.7%) (P < 0.02). After the last treatment there were also statistically significant differences between groups in perceived pain area (MPQ) and the use of weak analgesics (P < 0.03). There were no statistically significant changes in SCL or SF36 scores from baseline to t4. In conclusion, hypnosis seems to offer clinically relevant pain relief in PIOP, particularly in highly susceptible patients. However, stress coping skills and unresolved psychological problems need to be included in a comprehensive management plan in order also to address psychological symptoms and quality of life.

Intraoral somatosensory abnormalities in patients with atypical odontalgia - A controlled multicenter quantitative sensory testing study

&NA; Intraoral somatosensory abnormalities were commonly detected in atypical odontalgia patients, and agreement between quantitative and qualitative sensory testing was good to excellent. &NA; Intraoral somatosensory sensitivity in patients with atypical odontalgia (AO) has not been investigated systematically according to the most recent guidelines. The aims of this study were to examine intraoral somatosensory disturbances in AO patients using healthy subjects as reference, and to evaluate the percent agreement between intraoral quantitative sensory testing (QST) and qualitative sensory testing (QualST). Forty‐seven AO patients and 69 healthy control subjects were included at Universities of Washington, Malmö, and Aarhus. In AO patients, intraoral somatosensory testing was performed on the painful site, the corresponding contralateral site, and at thenar. In healthy subjects, intraoral somatosensory testing was performed bilaterally on the upper premolar gingiva and at thenar. Thirteen QST and 3 QualST parameters were evaluated at each site, z‐scores were computed for AO patients based on the healthy reference material, and LossGain scores were created. Compared with control subjects, 87.3% of AO patients had QST abnormalities. The most frequent somatosensory abnormalities in AO patients were somatosensory gain with regard to painful mechanical and cold stimuli and somatosensory loss with regard to cold detection and mechanical detection. The most frequent LossGain code was L0G2 (no somatosensory loss with gain of mechanical somatosensory function) (31.9% of AO patients). Percent agreement between corresponding QST and QualST measures of thermal and mechanical sensitivity ranged between 55.6% and 70.4% in AO patients and between 71.1% and 92.1% in control subjects. In conclusion, intraoral somatosensory abnormalities were commonly detected in AO patients, and agreement between quantitative and qualitative sensory testing was good to excellent.

Differential effect of intravenous S-ketamine and fentanyl on atypical odontalgia and capsaicin-evoked pain.

Abstract Atypical odontalgia (AO) is an intraoral pain condition of currently unknown mechanisms. In 10 AO patients and 10 matched healthy controls, we examined the effect of intravenous infusion of an N‐methyl‐d‐aspartate (NMDA) receptor antagonist S‐ketamine and a μ‐opioid agonist fentanyl on spontaneous AO pain and on an acute intraoral nociceptive input evoked by topical application of capsaicin. The drugs were administered in a randomized, placebo‐controlled, cross‐over manner. Furthermore, measures of intraoral sensitivity to mechanical and thermal quantitative sensory testing (QST) including temporal summation were compared between groups and sides. Both drugs failed to produce an analgesic effect on spontaneous AO pain, but fentanyl effectively reduced capsaicin‐evoked pain. AO patients showed increased sensitivity to capsaicin and heat pain, but no significant differences in cold and mechanical sensitivity compared with healthy controls. No side‐to‐side differences in QST measures were found in AO patients. The present study demonstrates that AO is unlikely to be primarily due to a persistent afferent barrage from the peripheral region. Furthermore, in contrast to studies on various neuropathic pain conditions, fentanyl and S‐ketamine in the present doses failed to attenuate AO pain.

An update on pathophysiological mechanisms related to idiopathic oro-facial pain conditions with implications for management

Chronic oro-facial pain conditions such as persistent idiopathic facial pain (PIFP), atypical odontalgia (AO) and burning mouth syndrome (BMS), usually grouped together under the concept of idiopathic oro-facial pain, remain a diagnostic and therapeutic challenge. Lack of understanding of the underlying pathophysiological mechanisms of these pain conditions is one of the important reasons behind the problems in diagnostic and management. During the last two decades, neurophysiological, psychophysical, brain imaging and neuropathological methods have been systematically applied to study the trigeminal system in idiopathic oro-facial pain. The findings in these studies have provided evidence for neuropathic involvement in the pathophysiology of PIFP, AO and BMS. The present qualitative review is a joint effort of a group of oro-facial pain specialists and researchers to appraise the literature on idiopathic oro-facial pain with special focus on the currently available studies on their pathophysiological mechanisms. The implications of the findings of these studies for the clinical diagnosis and treatment of idiopathic oro-facial pain conditions are discussed.

Effect of Systemic Monosodium Glutamate (MSG) on Headache and Pericranial Muscle Sensitivity

We conducted a double-blinded, placebo-controlled, crossover study to investigate the occurrence of adverse effects such as headache as well as pain and mechanical sensitivity in pericranial muscles after oral administration of monosodium glutamate (MSG). In three sessions, 14 healthy men drank sugar-free soda that contained either MSG (75 or 150 mg/kg) or NaCl (24 mg/kg, placebo). Plasma glutamate level, pain, pressure pain thresholds and tolerance levels, blood pressure (BP), heart rate and reported adverse effects were assessed for 2 h. No muscle pain or robust changes in mechanical sensitivity were detected, but there was a significant increase in reports of headache and subjectively reported pericranial muscle tenderness after MSG. Systolic BP was elevated in the high MSG session compared with low MSG and placebo. These findings add new information to the concept of MSG headache and craniofacial pain sensitivity.