Myofascial pain syndrome and its relation to trigger points, facial form, muscular hypertrophy, deflection, joint loading, body mass index, age and educational status

INTRODUCTION Myofascial pain (MFP), known also as myofascial pain syndrome (MPS), is a type of pain characterized by the presence of a trigger point (TrPs) in a taut band of skeletal muscles or its fascia.[12] Several factors have been linked to MFP including emotional and behavioral statuses, poor posture, muscular tension, and history of road traffic accidents (RTAs). Other comorbidities such as tension-type headaches and temporomandibular joint pain have also been reported to trigger an MFP episode.[3456] The proposed pathogenesis of MFP include interactions of varying intrinsic factors (i.e., central sensitization, decreased coping ability) and extrinsic factors (psychological, behavioral, and psychosocial factors) with consistent hypercontraction of sarcomeres forming TrPs within muscle tissues.[7] Due to continuous neural activation and action potential generation in these TrPs, an increase in secretion of myokines, inflammatory cytokines, and neurotransmitters with a reduction in blood flow will take place.[8910] These mechanisms combined with psychological stresses are believed to sensitize the muscle TrPs causing the patient’s symptoms.[411,12] Subjective symptoms of MFP in the head and neck region (HNMFP) often include continuous, dull aching pain that is present at rest and increases with function (jaw loading) varying from mild discomfort to debilitating pain.[1314] Objective finding commonly includes jaw deviation with function, aggravated by palpation of muscles of mastication during examination.[15] In general, diagnosis of HNMFP is a challenging process due to variation in the condition patterns and wide range of reported symptoms in addition to lack of adequate dental practitioners’ experiences in some occasions. Therefore, the diagnosis process mostly relies on a combination of detailed patient’s history, clinical examination, and imagining on a case-by-case basis.[1617] Inaccurate or late diagnoses are more likely to lead to improper intervention and exacerbation of patient’s symptoms. Based on the current literature, the prevalence of HNMFP varies among different communities. In the US, up to 85% of the general population may have experienced HNMFP at one point in life.[1] Out of all the cases, 30-85% would have a true TrPs with females being more affected than males with age range between 27 and 50 years.[1819] To deliver standard of care to patients in need, national data on prevalence of HNMFP is crucial. Therefore, the study aimed at evaluating the prevalence of HNMFP among the population of Jeddah, Saudi Arabia. We believe the outcome of this study will help to fill the gap in national databases on HNMFP and support the development of educational programs for the public as well as health care providers. MATERIALS AND METHODS A human research ethical approval was obtained through AlFarabi Dental College, Jeddah, Saudi Arabia. This was a cross-sectional study to survey a sample from residents of Jeddah, Saudi Arabi between the ages of 18–65 for HNMFP. The study exclusion criteria included (1) subjects who are not willing to undergo a thorough head and neck examination; (2) history of fibromyalgia or multiple complex medical conditions which could present with HNMFP-like signs and symptoms such as complex regional pain syndrome, psychiatric disorders, trauma or injury to the palpation site, neurological conditions and or rheumatologic disorders; and (3) participants who are currently on pain medications for any reason, antidepressant, anti-epileptic, and/or antipsychotic medication. The study was conducted at an annual public dental awareness event which took place over 3 days in Jeddah Waterfront Zone in December 2019. The event was held on a one-square-kilometer space with a total attendees 2500 attendees in which all were invited to participate in the study. Participants were first asked to complete a questionnaire composed of two sections. The first section included demographic questions on age, gender, educational level, marital status, and occupation. The second section was adopted from McGill pain questionnaire.[20] Including HNMFP-related questions, if present, such as symptoms’ onset, location, aggravating and alleviating factors, and pain location on a multiple view diagram. Next, all subjects had a comprehensive clinical examination completed by one of six calibrated co-investigators and included facial form, muscular hypertrophy, maximum vertical opening, deflection, and joint loading following Simons et al.[1] MFP diagnostic criteria. In addition, examination of upper quarter muscles (i.e., temporalis, masseter, sternocleidomastoid, and upper trapezius muscles) was completed using flat or pincer palpation as needed. Using this method, a TrP was identified when a pressure of 4kg/cm2 was applied for 5–10s to each muscle resulted in pain or tenderness.[1] Following completion of clinical examination, subjects were provided with an educational pamphlet on HNMFP and answered all questions related to condition diagnosis and management. In addition, referral information was provided to symptomatic participants for further management. For the purpose of this analysis, participants with one or more TrP were identified to have HNMFP. Collected data were summarized as frequencies and percentages. The presence of HNMFP was cross-tabulated with the demographic (i.e., age and gender). Then, group differences in pain characteristics, clinical examination, and presence of TrPs were tested using chi-square statistical method with a statistical significance value set at P < 0.05. IBM SPSS Statistics for Windows, version 23.0 was used to analyze the data. RESULTS A total of 197 subjects participated in the study with a response rate of 9.8%. Overall, 136 (69.0%) had signs and symptoms consistent with HNMFP. DEMOGRAPHICS About two-thirds (63.5%) of subjects were in the 18–35 age group and the remaining 36.5% aged between 36 and 65 years. In total, there were 113 (57.4%) males and (42.6%) females. In terms of educational levels, 29.9% had completed high school, 61.9% had a bachelor’s degree, and 8.1% had a master’s degree or higher. Overall, the risk of HNMFP was significantly associated with the educational status (P = 0.008). Categorization of subjects based on body mass index (BMI) showed that 56% were overweight or obese and 36.5% were within normal weight range. Accounting for BMI, overweight and obese subjects had higher tendency to report pain (P = 0.062). Details of study subjects’ demographics are listed in Table 1.Table 1: Demographics of study participantsCHARACTERISTICS OF SELF-REPORTED HNMFP The relation between HNMFP symptoms and both age groups and gender were investigated in this study. Overall, younger subjects reported pain to occur significantly more often on the right side (36.6% for younger subjects; 24.1% for older subjects) while older subjects were more likely to report pain on the left side (33.3% for older subjects; 15.9% for younger subjects) and the difference was statistically significant (P = 0.046). In terms of onset, older subjects were more likely to report spontaneous pain whereas younger subjects were more likely to report pain following trauma or a specific event (P = 0.049). Furthermore, male subjects were more likely to experience pain aggravation by pressure (15.4% vs. 3.4% in females) and cold (11.5% vs. none in females). Whereas female subjects were more likely to report jaw function (46.6% vs. 34.6% in males) as the main aggravating factor for pain (P = 0.015). Details of self-reported characteristics of HNMFP are listed in Table 2.Table 2: Characteristics of self-reported HNMFP (n = 136)CLINICAL EXAMINATION Comprehensive head and neck clinical examination was carried out for all subjects and categorized based on age and gender. Younger subjects were more likely to have symmetrical facial form compared to older subjects (96.3% vs. 81.5%; P = 0.004) while older subjects were more likely to have muscular hypertrophy compared to younger subjects (29.6% vs. 12.2%; P = 0.011). In addition, female subjects had deflection on opening more frequently compared to males (39.7% vs. 15.4%; P = 0.001). The distribution of joint loading showed a statistically significant difference between males and females (P = 0.008). Details of head and neck examination are included in Table 3.Table 3: Clinical examination of HNMFP subjects (n = 136)TRP SCREENING No significant differences in the presence of TrPs with relation to age were noted except for the left SCM which was more tender in older subjects (P = 0.006). In addition, female subjects showed a significantly higher frequency of positive TrPs in 10 examined muscles (of 14 in total) compared to males. Of all, 20.5% of male subjects had positive TrPs in right temporalis muscle compared to 41.4% in female subjects (P = 0.008). In addition, 14.1% of male subjects had positive TrPs in left temporalis muscle compared to 53.4% in female subjects (P < 0.001). For the right sternocleidomastoid muscle, 23.1% of male subjects had positive TrPs compared to 39.7% in female subjects (P = 0.037). At the same time, TrPs frequency in the right trapezius muscle was reported in 34.6% of males compared to 51.7% in females (P = 0.046). Details of TrPs screening are included in Table 4.Table 4: Presence of TrPs in examined muscles (n = 136)DISCUSSION HNMFP is a fairly common condition with major impact on social and professional life. Several management approaches have been propose and are usually tailored to each patient based on symptoms distribution and severity. It includes analgesics such as paracetamol, nonsteroidal anti-inflammatory medications, opioids, and/or physical therapies including myofascial TrP massage, ischemic compression, and acupuncture.[212223] Based on the literature, treatment duration of MFP varies and is strongly related to MFP onset. Patients with acute onset are more likely to have their symptoms resolve spontaneously or with minimal intervention in few weeks. Only a small percentage of patients may progress into a chronic status as experienced pain could last up to 6 months. On the contrary, the prognosis of chronic MFP is less predictable, and the average duration of symptoms may reach up to 63 months.[2425] Several, smaller studies have looked at the prevalence of self-reported HNMFP in different cities of Saudi Arabia and ranged between 22.4% and 42%.[26] Only few studies on HNMFP have been conducted in Jeddah, the second-largest city of Saudi Arabia, which creates a significant challenge from a public health point of view to understand this condition and develop national prevention and management programs for the general public. In addition, the potential relation between BMI and HNMFP reported in this study is of a great interest considering Saudi Arabia to have one of the highest obesity incidence in general population in addition to other chronic diseases such as hypertension and hyperlipidemia. We believe our study will be a great addition to the database of this region and HNMFP literature, which would facilitate future larger funded studies with focus on pathogenesis and intervention.[272829] The present study is based on a self-reported questionnaire combined with clinical examination for subjective findings. Overall, 136 (69%) subjects had at least one tender muscle and were assigned the diagnosis of HNMFP. Several risk factors for HNMFP were evaluated in this study. Overweight and obese subjects had higher tendency to report muscle pain than normal or underweight individuals, similar to what have been reported in the literature previously.[30] Available evidence suggests that obesity is associated with low-grade chronic inflammatory state where inflammatory markers such as C-reactive protein, IL-6, TNF, and serum cortisol were found to be elevated which may have a role in altering pain modulation in HNMFP individuals.[31] In addition, the increase in mechanical stresses caused by overweight results in further production of proinflammatory cytokines from chondrocytes to overexpress body pain. Lower educational status was another factor investigated in this study, and was significantly related to report of muscle pain by participants (P = 0.008). This finding was in line with what have been reported by Janevic et al.[32] in which prevalence of chronic pain in subjects suffering from arthritis, cancer, diabetes, heart disease, high blood pressure, and lung disease was association with lower education degree. Analyzing HNMFP triggers in relation to age group, older subjects experienced spontaneous pain without a trigger. However, younger subjects were more likely to have a triggering event such as trauma followed by HNMFP onset. One explanation could be the anticipated higher levels of physical activities among younger population and increased risk for trauma which can take different forms. One in particular is the use of simultaneous electronic devices which has been linked to musculoskeletal pain in adolescents within a school-based study.[33] The role of gender was considered in this study as female subjects significantly showed a higher prevalence of positive TrPs compared to males. This relation in particular has always been immense and unclear. Diverse theories in relation to gender were proposed including links to genetics and hormonal changes such as menstrual cycle, pregnancy, and oral conceptive use which may exaggerate HNMFP symptoms.[34] At the same time, women are more likely to be vocal and tend to report pain more often than men.[35] In the current study, pain aggravating factors varied in relation to gender as male subjects were more likely to experience pain with pressure and cold. However, female subjects were more likely to report jaw function as the main aggravating factor for pain (P = 0.015). These findings are consistent with what was reported by Mogil et al.[36] and indicated sex differences to affect certain pain modalities compared to others such as in heat or pressure-induced pain and ischemic pain. At the same time, Spierings et al.[37] concluded that joint loading or function (chewing, eating, and talking) are more likely to aggravate HNMFP in females. However, a recent systematic review evaluated the relation between gender and pain perception in a total of 122 studies and reported cold and pressure to aggravate pain more often in females than males, which contradicts our findings.[38] This study has several limitations. First, the study participants were recruited from a single event location and generalization to all population of Jeddah is not applicable especially for difference in socioeconomic levels. Furthermore, study subjects were invited to participate in the study during the event and were more likely to be educated, healthy, and self-aware due to the event setup and location. However, our result showed diversity, specifically in gender and age groups, which may compensate for this issue to a certain capacity. Second, the study was conducted in the city of Jeddah and future studies are needed to better understand the prevalence of HNMFP in all population of Saudi Arabia. CONCLUSION MFP in the head and neck region is a common condition among adult population of Jeddah with more female subjects experiencing a significantly higher frequency of positive TrPs compared to males. In addition, factors such as BMI and educational level were found to be linked to HNMFP. Younger subjects were more likely to have symmetrical facial form while older subjects were more likely to have muscular hypertrophy. The distribution of joint loading showed a statistically significant difference between males and females with females having deflection on opening more frequently compared to males. Acknowledging the prevalence of HNMFP is important for future assessment, better understanding and management of such chronic pain condition. Further studies with larger group of patients are needed to confirm these findings. FINANCIAL SUPPORT AND SPONSORSHIP Nil. CONFLICTS OF INTEREST There are no conflicts of interest. AUTHORS CONTRIBUTIONS Not applicable. ETHICAL POLICY AND INSTITUTIONAL REVIEW BOARD STATEMENT The procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation at AlFarabi Dental College, Jeddah, Saudi Arabia. Prior to launching the study, a human research ethical approval was obtained as stated in the manuscript (ethical approval reference number 20-08/6). PATIENT DECLARATION OF CONSENT Not applicable. DATA AVAILABILITY STATEMENT Not applicable. ACKNOWLEDGEMENT This study was conducted at a public dental awareness event which took place in Jeddah Waterfront and ethical approval was obtained through AlFarabi Dental College, Jeddah, Saudi Arabia. We thank the following students for their impressive work in the data collection process: Turki Babaeer, Aya Hussein, Maram Alras, Ghith Aldhahri, and Anas Aljowaied.

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