Effects of nerve growth factor experimentally-induced craniofacial muscle sensitization on referred pain frequency and number of headache days: A double-blind, randomized placebo-controlled study.

OBJECTIVE: To assess if repeated intramuscular injections of nerve growth factor into the temporalis and masseter muscles increase mechanical sensitivity and entropy scores. Furthermore, to investigate if increased mechanical sensitivity would lead to increased prevalence of referred pain in the studied individuals. Finally, if increased muscle sensitization would lead to an increase in number of headache days during the experimental period. METHODS: The present double-blind, randomized placebo-controlled study recruited 16 healthy participants who were injected with nerve growth-factor, on 2 days, into the masseter and temporalis muscles and isotonic saline on the contralateral side. Mechanical sensitivity was assessed at seven different time-points (total of 21 days) by application of three different forces to 15 different sites of both muscles. Participants were asked after each force application if they experienced referred pain and were asked to keep a headache diary during the experimental period. RESULTS: In summary, a) repeated intramuscular injections of nerve-growth-factor caused an increase in mechanical sensitivity for the masseter but not the temporalis muscle, and an increase in entropy scores when compared to the isotonic saline side. b) Both referred pain frequency and number of headache days were not increased following nerve-growth-factor injections. CONCLUSIONS: These findings support the idea that mechanical sensitization in the masseter and temporalis muscles differs following injections of nerve growth factor. Furthermore, referred pain and headache frequency do not seem to be related to nerve growth factor sensitization in this model. These findings support the idea that in healthy individuals referred pain may be an epiphenomenon of the muscle in response to noxious input.

Usefulness of cordotomy in patients with cancer who experience bilateral pain: implications of increased pain and new pain.

BACKGROUND: Although mirror pain occurs after cordotomy in patients experiencing unilateral pain via a referred pain mechanism, no studies have examined whether this pain mechanism operates in patients who have bilateral pain. OBJECTIVE: To assess the usefulness of cordotomy for bilateral pain from the viewpoint of increased pain or new pain caused by a referred pain mechanism. METHODS: Twenty-six patients who underwent percutaneous cordotomy through C1-C2 for severe bilateral cancer pain in the lumbosacral nerve region were enrolled. Pain was dominant on 1 side in 23 patients, and pain was equally severe on both sides in 3 patients. Unilateral cordotomy was performed for the dominant side of pain, and bilateral cordotomy was performed for 13 patients in whom pain on the nondominant side developed or remained severe after cordotomy. RESULTS: After unilateral cordotomy, 19 patients (73.1%) exhibited increased pain, which for 14 patients was as severe as the original dominant pain. After bilateral cordotomy, 7 patients (53.4%) exhibited new pain, which was located cephalad to the region rendered analgesic by cordotomy and was better controlled than the original pain. No pathological organic causes of new pain were found in any patient, and evidence of a referred pain mechanism was found in 3 patients after bilateral cordotomy. CONCLUSION: These results show that a referred pain mechanism causes increased or new pain after cordotomy in patients with bilateral pain. Nevertheless, cordotomy can still be indicated for patients with bilateral pain because postoperative pain is better controlled than the original pain.

Incidence and characteristics of acute referred orofacial pain caused by a posterior single tooth pulpitis in an Iranian population.

INTRODUCTION: This study was designed to evaluate incidence and characteristics of acute referred orofacial pain caused by a posterior single tooth pulpitis in an Iranian population. METHODS: In this cross-sectional study, 3,150 patients (1,400 males and 1,750 females) with pain in the orofacial region were evaluated via clinical and radiographic examination to determine their pain source. Patients completed a standardized clinical questionnaire consisting of a numerical rating scale for pain intensity and chose verbal descriptors from short form McGill questionnaire to describe the quality of their pain. Visual analog scale (VAS) was used to score pain intensity. In addition, patients indicated sites to which pain referred by drawing on an illustration of the head and neck. Data were analyzed using chi-square, fisher exact, and Mann-Whitney tests. RESULTS: Two thousand and hundred twenty patients (67/3%) reported pain in sites that diagnostically differed from the pain source. According to statistical analysis, sex (P = 0.02), intensity of pain (0.04), and quality (P = 0.001) of pain influenced its referral nature, while age of patients and kind of stimulus had no considerable effect on pain referral (P > 0.05). CONCLUSION: The results of the present study show the prevalence of referred pain in the head, face, and neck region is moderately high. Therefore, in patients with orofacial pain, it is essential to carefully examination before carrying out treatment that could be inappropriate.

Characteristics of referred muscle pain to the head from active trigger points in women with myofascial temporomandibular pain and fibromyalgia syndrome.

Our aim was to compare the differences in the prevalence and the anatomical localization of referred pain areas of active trigger points (TrPs) between women with myofascial temporomandibular disorder (TMD) or fibromyalgia (FMS). Twenty women (age 46 ± 8 years) with TMD and 20 (age 48 ± 6 years) with FMS were recruited from specialized clinic. Bilateral temporalis, masseter, sternocleidomastoid, upper trapezius, and suboccipital muscles were examined for TrPs. TrPs were identified by palpation and considered active when the pain reproduced familiar pain symptom experienced by the patient. The referred pain areas were drawn on anatomical maps, digitalized and also measured. A new analysis technique based on a center of gravity (COG) method was used to quantitative estimate of the localization of the TrP referred pain areas. Women with FMS exhibited larger areas of usual pain symptoms than women with myofascial TMD (P < 0.001). The COG coordinates of the usual pain on the frontal and posterior pain maps were located more superior in TMD than in FMS. The number of active TrPs was significantly higher in TMD (mean ± SD 6 ± 1) than in FMS (4 ± 1) (P = 0.002). Women with TMD exhibited more active TrPs in the temporalis and masseter muscles than FMS (P < 0.01). Women with FMS had larger referred pain areas than those with TMD for sternocleidomastoid and suboccipital muscles (P < 0.001). Significant differences within COG coordinates of TrP referred pain areas were found in TMD, the referred pain was more pronounced in the orofacial region, whereas the referred pain in FMS was more pronounced in the cervical spine. This study showed that the referred pain elicited from active TrPs shared similar patterns as usual pain symptoms in women with TMD or FMS, but that distinct differences in TrP prevalence and location of the referred pain areas could be observed. Differences in location of referred pain areas may help clinicians to determine the most relevant TrPs for each pain syndrome in spite of overlaps in pain areas.

Referred dental pain, an analysis of their prevalence and clinical implication / Dolor dental referido, análisis de su prevalencia e implicancias clínicas

The study objective was to evaluate the prevalence of referred dental pain (RDP) in a group of Brazilians subjects and identify possible partnerships with sex, age and the presence of periodontal or periapical lesions. A descriptive cross-sectional study was designed, 98 patients between 14 and 64 years old (59 women and 39 men), who consulted by dental pain were evaluated clinically and radiographically in order to determine the cause and partnership with periapical and periodontal lesions and its possible territories projection other than their origin. The prevalence of RDP was 31.6 percent, higher in women (67.74 percent) though without statistical significance. The RDP was presented at a 45.16 percent together with periapical lesion and a 25.8 percent along with periodontal lesion. There was no relationship between age and RDP presence. The high prevalence of RDP found reinforces the need for a diagnosis of orofacial pain.

El objetivo de este estudio fue analizar la prevalencia de dolor referido dental (DRD) en un grupo de sujetos brasileros y determinar las posibles asociaciones con sexo, edad y la presencia de lesión periapical o periodontal. Se diseñó un estudio descriptivo de corte transversal, con 98 pacientes, de entre 14 y 64 años (59 mujeres y 39 hombres), que consultaron por dolor dental, ellos fueron evaluados clínica y radiográficamente con el fin de determinar la causa y la asociación con lesión periapical y periodontal y su posible proyección a territorios distintos de su origen. La prevalencia del DRD fue de 31,6 por ciento, mayor en mujeres (67,74 por ciento) aunque sin significancia estadística. El DRD se presentó en un 45,16 por ciento junto con lesión periapical y un 25,8 por ciento junto a lesión periodontal. No se encontró asociación entre la edad y la presencia de DRD. La alta prevalencia de DRD encontrada refuerza la necesidad de un diagnóstico etiológico del dolor orofacial.

Referred pain from myofascial trigger points in head, neck, shoulder, and arm muscles reproduces pain symptoms in blue-collar (manual) and white-collar (office) workers.

OBJECTIVE: To describe the prevalence and referred pain area of trigger points (TrPs) in blue-collar (manual) and white-collar (office) workers, and to analyze if the referred pain pattern elicited from TrPs completely reproduces the overall spontaneous pain pattern. METHODS: Sixteen (62% women) blue-collar and 19 (75% women) white-collar workers were included in this study. TrPs in the temporalis, masseter, upper trapezius, sternocleidomastoid, splenius capitis, oblique capitis inferior, levator scapulae, scalene, pectoralis major, deltoid, infraspinatus, extensor carpi radialis brevis and longus, extensor digitorum communis, and supinator muscles were examined bilaterally (hyper-sensible tender spot within a palpable taut band, local twitch response with snapping palpation, and elicited referred pain pattern with palpation) by experienced assessors blinded to the participants' condition. TrPs were considered active when the local and referred pain reproduced any symptom and the patient recognized the pain as familiar. The referred pain areas were drawn on anatomic maps, digitized, and measured. RESULTS: Blue-collar workers had a mean of 6 (SD: 3) active and 10 (SD: 5) latent TrPs, whereas white-collar workers had a mean of 6 (SD: 4) active and 11 (SD: 6) latent TrPs (P>0.548). No significant differences in the distribution of active and latent TrPs in the analyzed muscles between groups were found. Active TrPs in the upper trapezius, infraspinatus, levator scapulae, and extensor carpi radialis brevis muscles were the most prevalent in both groups. Significant differences in referred pain areas between muscles (P<0.001) were found; pectoralis major, infraspinatus, upper trapezius, and scalene muscles showed the largest referred pain areas (P<0.01), whereas the temporalis, masseter, and splenius capitis muscles showed the smallest (P<0.05). The combination of the referred pain from TrPs reproduced the overall clinical pain area in all participants. CONCLUSIONS: Blue-collar and white-collar workers exhibited a similar number of TrPs in the upper quadrant musculature. The referred pain elicited by active TrPs reproduced the overall pain pattern. The distribution of TrPs was not significantly different between groups. Clinicians should examine for the presence of muscle TrPs in blue-collar and white-collar workers.

Prevalence and anatomical localization of muscle referred pain from active trigger points in head and neck musculature in adults and children with chronic tension-type headache.

OBJECTIVE: To compare differences in the prevalence and the anatomical localization of the referred pain areas of active trigger points (TrPs) in head and neck musculature between adults and children with chronic tension-type headache (CTTH). DESIGN: A cross-sectional study. SETTING: Some studies had found that referred pain from active TrPs reproduce the head pain pattern in adults. No study has compared clinical differences between referred pain patterns elicited by active TrPs between adults and children with CTTH. PATIENTS: Twenty adults (10 men, 10 women, mean age: 41 ± 11 years) and 20 children (10 boys, 10 girls, mean age: 8 ± 2 years) with CTTH were included. OUTCOME MEASURES: Bilateral temporalis, sternocleidomastoid, upper trapezius, and suboccipital muscles were examined for TrPs. TrPs were identified by palpation and considered active when local and referred pains reproduce the headache pain attacks. The referred pain areas were drawn on anatomical maps, digitalized, and also measured. An analysis technique based on a center of gravity (COG) method was used to provide a quantitative estimate of the localization of the TrP referred pain areas. RESULTS: Adults with CTTH exhibited a greater years with headache, higher intensity, and longer headache duration (P < 0.05) compared with children. The COG coordinates of the spontaneous pain on the dominant side were located more anterior (higher X-value), and spontaneous pain in the frontal and posterior areas was located more inferior (lower Y-value) in adults than in children. The number of active muscle TrPs was significantly higher (P = 0.001) in adults with CTTH (mean ± standard deviation [SD]: 4 ± 0.8) as compared with children (mean ± SD: 3 ± 0.7). Children with CTTH had larger referred pain areas than adults for upper trapezius, sternocleidomastoid, and temporalis (P < 0.001) muscles. The COG coordinates of the referred pain areas of temporalis and sternocleidomastoid muscle TrPs were more inferior (lower Y-values) in adults than in children with CTTH. CONCLUSIONS: This study showed that the referred pain elicited from active TrPs shared similar pain patterns as spontaneous CTTH in adults and children. Differences in TrP prevalence and location of the referred pain areas can be observed between adults and children with CTTH.

Comorbidity of pterygoid hamular area pain and TMD.

Often craniofacial pain subjects report a number of conflicting and overlapping symptoms that can present a confusing clinical picture. Reaching a diagnosis on these individuals can prove to be a frustrating and difficult event for both the examiner and the patient. Thus, it is incumbent on clinicians treating patients with pain in the head, face and neck areas to be familiar with the less common pain disorders to assist in the differential review. This retrospective study examines the comorbidity of pterygoid hamulus pain with temporomandibular disorders (TMD). To acquire this information, the charts of 464 subjects with TMD in a private setting were examined to determine if pterygoid hamular pain was found at the evaluation. Ninety-two patients (N=92) had positive findings. Areas of referred pain that were elicited during the examination were charted. The pterygoid hamular area should be evaluated in individuals with TMD and especially those presenting with posterior palate and throat pain.

Prevalence of and referred pain from myofascial trigger points in the forearm muscles in patients with lateral epicondylalgia.

OBJECTIVE: Referred pain and pain characteristics evoked from the extensor carpi radialis brevis, extensor carpi radialis longus, extensor digitorum communis, and brachioradialis muscles was investigated in 20 patients with lateral epicondylalgia (LE) and 20-matched controls. METHODS: Both groups were examined for the presence of myofascial trigger points (TrPs) in a blinded fashion. The quality and location of the evoked referred pain, and the pressure pain threshold (PPT) at the lateral epicondyle on the right upper extremity (symptomatic side in patients, and dominant-side on controls) were recorded. Several lateral elbow pain parameters were also evaluated. RESULTS: Within the patient group, the elicited referred pain by manual exploration of 13 out of 20 (65%) extensor carpi radialis brevis muscles, 12/20 (70%) extensor carpi radialis longus muscles, 10/20 (50%) brachioradialis muscles, and 5/20 (25%) extensor digitorum communis muscles, shares similar pain patterns as their habitual lateral elbow and forearm pain. The mean number of muscles with TrPs for each patient was 2.9 [95% confidence interval (CI) 1,4] of which 2 (95% CI 1,3) were active, and 0.9 (95% CI 0,2) were latent TrPs. Control participants only had latent TrPs (mean: 0.4; 95% CI 0,2). TrP occurrence between the 2 groups was significantly different for active TrPs (P<0.001), but not for latent TrPs (P>0.05). The referred pain pattern was larger in patients than in controls, with pain referral to the lateral epicondyle (proximally) and to the dorso-lateral aspect of the forearm in the patients, and confined to the dorso-lateral aspect of the forearm in the controls. Patients with LE showed a significant (P<0.001) lower PPT (mean: 2.1 kg/cm; 95% CI 0.8, 4 kg/cm) as compared with controls (mean: 4.5 kg/cm; 95% CI 3, 7 kg/cm). Within the patient group, PPT at the lateral epicondyle was negatively correlated with both the total number of TrPs (rs=-0.63; P=0.003) and the number of active TrPs (rs=-0.5; P=0.02): the greater the number of active TrPs, the lower the PPT at the lateral epicondyle. DISCUSSION: Our results suggest that in patients with LE, the evoked referred pain and its sensory characteristics shared similar patterns as their habitual elbow and forearm pain, consistent with active TrPs. Lower PPT and larger referred pain patterns suggest that peripheral and central sensitization exists in LE.