Complementary Effect of Electro Acupuncture on Refractory Head and Neck Myofascial Pain: A Retrospective Investigation of Patient-Reported Outcomes

2.1. Inclusion Criteria

The inclusion criteria for this investigation were as follows: (a) adult patients aged 18-85; (b) patients subjective reporting of pain/discomfort in the face, TMJ area, and/or neck using the numeric rating scale (NRS) prior to the initiation of any treatment modalities; (c) objective confirmation of primary chronic myalgia/myofascial pain based on the RDC-TMD and DC-TMD [14] through clinical and radiographic examination by an orofacial pain expert; (d) persistent pain for 3 months or more; (e) documentation of none, one, or more accompanying symptoms (i.e. TMJ sound, tinnitus/stuffy ear, otalgia, and/or headache; (f) documentation of presence or absence of concurrent pharmacotherapeutics (i.e. analgesics, opioids, muscle relaxants, and/or anxiolytics); g) documentation of presence or absence of other supportive modalities such as physical therapy (PT), home self-care (i.e. thermal packs and masticatory/neck muscles exercises), and/or trigger points/Botox injections, (h) all included patients received either an OA or a combination of OA and traditional Chinese/Japanese AC or electroacupuncture, (i) documentation of adequate number of AC treatment sessions (minimum of 5 sessions) starting at 1 month ±2 weeks after the insertion of the OA, (j) adequate documentation of short-term and long-term follow ups, including patients-reported NRS scores, in the patient’s records (detailed follow-up time-point for both groups is included in the data collection section).

2.2. Exclusion Criteria

Charts of patients who did not have confirmed primary chronic face, TMJ, and/or neck myalgia/myofascial pain were not considered in this study. Those with neuropathic orofacial pain or temporomandibular disorder related to rheumatoid/connective tissue disorders were excluded. Patients with severe cognitive or mental disabilities that compromise their ability to understand and/or fill the NRS and those with uncontrolled psychological disorders that may affect their perception of treatment outcomes, were also excluded.

2.3. Data Collection

2.4. Data Analysis

Standard descriptive statistics included means and standard deviations as well as frequencies for the measured variables. Bivariate analyses included Mann–Whitney U, Spearman correlation, chi-square and Fisher exact test. Longitudinal analyses were carried out using repeated-measures ANOVA to test the interaction between the 2 groups and 3 time points. Changes in measures of NRS scores between 2 points of time were analyzed by the Wilcoxon signed rank test, while comparing between the 2 groups at any certain point of time was conducted by a Mann-Whitney U test. Multiple linear regression analysis was conducted to control for the effect of potential significant confounders in the bivariate analyses. The data analysis was conducted through SAS statistical software (version 9.1.3; SAS Institute, Cary, NC). All statistical analysis was considered statistically significant if p < 0.05. The raw data used for statistical analyses and to support the findings of this study have been deposited in the Tufts Box repository at https://tufts.box.com/s/e4a7pubz5gyshx5llrsfxr80yx5q7lcl.

3.1. Baseline Characteristics and Demographics

A total of 191 patients’ charts, both paper and electronic, were retrieved from TUSDM records database. Eighty-eight patients’ charts were excluded due to missing data, lacking ICD-9/ICD-10 specific TMD diagnosis, inadequate short-term or long-term follow-ups information, and/or presence of one or more of the study exclusion criteria.

A total of 103 patients’ charts were deemed eligible for further review based on the study’s inclusion and exclusion criteria. Among those, 57 received OA and 48 patients received a combination therapy of OA/AC (Fig. 1).

Out of the 103 patients, 80 (77.7%) were females. The mean age of the entire study population was 53.2 years (SD= ±16.3) with a higher mean age in the OA/AC group compared with the OA group, but with no significant statistical difference (P= 0.497) (Table 1).

In both groups, the most common medical comorbidities were psychiatric disorders (39.8%), respiratory diseases (33.3%), and cardiovascular diseases (33%), with no significant difference in their distribution among the two groups (P=0.958, 0.527, 0.885, respectively) (Table 2). Endocrine disorders, mainly hypothyroidism, were the only medical comorbidity that had a significantly higher number in the OA/AC group compared to OA (P= 0.040), in which regression analysis was further perused (Table 2).

All patients had a primary diagnosis of chronic myalgia/myofascial pain. In both OA and OA/AC groups, 74.8% were diagnosed with myofascial pain in both masticatory and neck muscles, while 22.3% had myofascial pain in masticatory muscles only (Table 2). Secondary diagnoses were equally distributed among both comparison groups except for articular risk disorders (ICD-9: 524.6; ICD-10: M26.63), and other jaw pains (ICD-9: 784.92; ICD-10: R68.84) in which numbers were significantly higher in the OA group compared to OA/AC group (P= 0.047 and P=0.001, respectively) (Table 2).

Concurrent supportive therapies were indicated in the patients’ chart with the majority being prescribed systemic medications (94%) followed by PT (35%). No significant statistical differences in the utilization of supportive therapies were shown between the 2 groups. Table 2 provides details about the modalities of supportive therapies and their distribution among the groups.

3.2. Changes in NRS scores from Baseline, within and in between Groups

4.1. Primary Outcomes

This study demonstrated that AC may be an effective complementary modality in cases of primary chronic myofascial pain that remains refractory after OA therapy. In patients with refractory TMJ and/or neck pain, the addition of AC to OA therapy exhibited a pain/discomfort relieving effect comparable to the relieved OA respondents experienced. Patients with face pain in both groups experienced significant improvement with OA therapy (with more abundance in the OA group). Patients who improved, but were not completely satisfied with OA therapy results in OA/AC group received additional AC treatment, which increased the significance of their improvement and brought it to a level comparable to that experienced by the OA group.

Several investigations have compared the effectiveness of AC to other conventional treatment modalities in managing head and neck chronic myofascial pain. In a randomized clinical trial (RCT), Itoh and colleagues compared the effect of trigger point AC with sham AC in 13 patients diagnosed with chronic myofascial pain. After 10 weeks of treatment, they reported a significant reduction in pain intensity scores in the trigger point AC group compared to the sham group. However, no significant improvement was demonstrated in the mandibular range of motion [18]. Moreover, List et al. conducted an RCT for 110 patients diagnosed with TMDs of primarily muscular origin. The study compared the effect of AC (6 sessions) with OA (7-8 weeks) in treating TMD symptoms. While a reduction in pain intensity was witnessed in both treatment groups, AC was significantly superior to OA therapy [19].

In the contrary, Johansson and colleagues found that both AC and OA therapy significantly lowered the subjective symptoms and clinical signs of muscle-originated TMDs, with no significant difference between the two groups at 3-month follow-up. They concluded that AC may be used as an alternative method for patients who lack compliance with occlusal splint therapy [20].

Only a few studies evaluated the complementary role of AC in managing head and neck myofascial pain that has been refractory to conventional therapy. Goddard, in his retrospective study of 25 patients, generated the theory that AC may play a significant complementary role in managing a patient with chronic orofacial pain. The study called for future investigations in which a bigger number of study participants, comparison with placebo, and assessment of long-term outcomes should be considered [21]. Ferreira et al., conducted an RCT of 20 patients diagnosed with TMD in which the control group received OA therapy versus the test group that received a combination of OA and AC. In concordance with the findings from our study, they concluded that AC exhibits a significant synergetic effect with OA therapy that may expedite symptoms and relieve them. The longevity of the effect could not be concluded from the study due to the lack of long-term follow‐up [22]. List et al. retrospectively investigated the effectiveness of OA therapy versus AC in managing myogenic TMDs in a cohort of 80 patients. It was concluded that both modalities were comparably effective at both short-term and long-term follow-ups (i.e. 6- and 12-month follow-ups). However, the findings from their study failed to show a significant effect of AC/OA combination therapy in refractory cases, which contradicts the results obtained from our study [23].

4.2. Secondary Outcomes

TMJ sound was significantly improved in both groups at short-and long-term follow-ups. The further improvement in TMJ sound in OA/AC group after the addition of AC treatment might have played an indirect role by reducing the tightness of masticatory muscles related to TMJ. However, this result should be taken with skepticism as this improvement might be related to the prolonged use of OA, which was proven to be significantly effective from the very beginning.

Additional AC therapy did not improve refractory tinnitus/stuffy ear symptoms in OA/AC group in comparison to the patients who received OA alone. Strom et al. demonstrated, in their clinical study, that combining AC and intraoral splints had a favorable effect on tinnitus, which contradicts the findings obtained in this investigation [24].

Otalgia and headache were significantly reduced in both OA and OA/AC groups at short-term follow-up (with OA therapy only). Improvement also continued at long-term follow-up which may question any additive effect of AC in managing both symptoms. Kostrzewa-Janicka et al., concluded similar results in their clinical study of 43 patients. where OA therapy was effective in managing patients with myofascial pain and tension-type headache [25]. Xue et al., reported in their crossover RCT that electroacupuncture was effective in managing tension-type headache [26]. On contrary to our results, an RCT by Saha et al., found that combining OA with usual care in patients with chronic headache and comorbid TMD yielded no superior effectiveness in treating headache compared to usual care alone [27].

4.3. Confounding Effects on Outcomes

Interestingly, the study demonstrated that the higher number of subjects with hypothyroidism in OA/AC group has created a confounding effect that may have hindered the effectiveness of OA and AC therapies on all outcome measures. Hypothyroidism is associated with persistent chronic myalgia due to reduction of thyroid hormone (T3) levels and elevation of thyroid-stimulating hormone (TSH) [28]. Moreover, feedback elevation of reverse T3 (rT3) along with an increase in TSH level in patients with hypothyroidism may play an important role in both chronic myofascial pain and fibromyalgia development [29]. This may have contributed to the lack of response to OA alone in the OA/AC group at short-term follow-up. The significant improvement of these refractory cases after adding AC therapy may not only be related to the AC analgesic effect but rather correlated to an underlying mechanism to manage thyroid hormone imbalance [30].

4.4. Study Strengths and Limitations

In this retrospective study, the efficacy of AC, as an adjunctive treatment modality, comes in support of findings from several clinical investigations where evidence for efficacy and safety of electro-acupuncture was proven. Chen et al. demonstrated the efficacy and safety of long-term transcutaneous electroacupuncture in managing delayed gastric emptying after distal gastrectomy [31]. In a randomized clinical trial, Cai et. al. provided evidence for the efficacy and safety of electroacupuncture for post-stroke depression [32]. Moreover, an open-label study, by Wang et. al., proved the clinical efficacy and safety of electro-acupuncture for diabetic peripheral neuropathy [33].

The retrospective nature of this study has limited the ability to obtain accurate and highly standardized information. Thus, readers should bear in mind that the continuation of improvements in some of the outcomes could be partially attributed to concurrent interventions aiming to manage other patient-reported complaints. Moreover, missing data has led to the exclusion of a significant number of patients, especially those who received AC only. This hindered investigation of the effect of AC in the third comparison arm. In addition, the diagnosis of chronic myalgia/myofascial pain was based on the combined RDC-TMD and DC-TMD diagnostic criteria, which may have compromised the homogeneity of the study population. Information regarding intra-oral findings, such as tooth wear, and reporting of parafunctional activities were lacking in this study. Such information should be collected and precisely documented during dental examination in future studies. Furthermore, undetailed documentation regarding the specifications of OA therapies and the duration of their daily use may have masked some of the modifying effects that would skew the outcomes of the interventions.