DISCUSSION
Myofascial pain syndrome is more prevalent than it is assumed to be. Furhermore, its occurrence should be considered in HSP rehabilitation as a primary etiology or sometimes accompanying the primary pathology.15 Studies have described it as an underdiagnosed issue since it is frequently overlooked. HSP has a complex mechanism in which nociceptive and neuropathic pains play a role.16 Conditions such as muscle imbalance, postural disorders, immobilization, and emotional stress in stroke patients may cause both the emergence of MTrP and the activation of latent MTrP in the shoulder region.6,13 As a result, a multimodal treatment approach is offered by both attempting to restore the neurological deficit and targeting MTrP. In this context, this study aimed to evaluate whether combining DN treatment with conventional rehabilitation contributes to improving pain, joint range of motion, and functionality parameters and clarify the significance of MTrP in HSP. While designing the study, we aimed to evaluate the parameters of pain, joint range of motion, and functionality at the end of three months. Therefore, the included patient population was clearly standardized and the frequently affected muscles in the shoulder girdle and periscapular region were targeted. The results showed that DN treatment did not provide an extra advantage on pain and functionality in HSP in the subacute period but contributed to improving joint range of motion both in the acute and subacute periods.
The prevalence of MTrP is higher in patients with HSP compared to that in the healthy population.6 Moreover, studies have emphasized the importance of both latent trigger points and active trigger points in HSP and stated that the number of MTrP may be correlated with pain and dysfunction.6 Among the studies examining MTrP in HSP treatment, there are some current ones using the myofascial release technique, local anesthesia, and DN treatments.12-14,17 In general, these studies combined MTrP therapy with conventional rehabilitation. Indeed, evaluating MTrP treatment as the primary treatment would be an incomplete approach for a complex pathology like HSP.
Neurophysiological mechanisms leading to anti-nociceptive effects on the myofascial trigger point and central nervous system can be initiated by DN treatment.18 Spinal dorsal horn activity is modulated by eliminating the source of peripheral nociception, and peripheral and central sensitization can be reduced by activating central inhibitory pain pathways.18,19 Moreover, with the elimination of the pain-spasm-pain vicious cycle, pain relief and improvement in joint range of motion is achieved, contributing to the biomechanics of the region.20,21
There are a limited number of publications on DN treatment for HSP. DiLorenzo et al., for instance, administered conventional rehabilitation to one group and DN treatment combined with conventional rehabilitation to the other group of patients with HSP.14 The results showed that there was a statistically greater improvement in pain level in the acute period in the DN group. Similarly, in our study, there was a greater improvement in posttreatment pain level in the DN group. However, this difference was no longer significant in the third month. In the studies of Dilorenzo et al., the lack of standardization in applying DN to the muscles was a disadvantage; while there were many applications on some muscles during the conventional treatment, some muscles received only two sessions.
Another point is that the aforementioned study evaluated functionality with mobility, and superior results were observed in the DN group. On the other hand, in our study, more objective and specific assessment scales for the upper extremity were used, and more improvement was observed in the DN group after treatment. However, there was no difference between the groups on the third month. Previous studies have reported that latent MTrPs also affect functionality in patients with HSP, and the fact that latent MTrPs were not treated in our study may have led to this result.6
Mendigutia-Gomez A. et al. found that the combination of conventional rehabilitation and single-session DN treatment reduced HSP more in the acute period compared to only conventional rehabilitation.12 While the results after treatment were similar in our study, this difference was not observed in the third month. The rehabilitation in our study, unlike the mentioned study, was in the form of a protocol covering a certain period for each group in accordance to the literature. Similarly, there were three sessions based on the general application of DN in sessions. Another important dissimilarity in our study is the demonstration of data for the subacute period. Furthermore, the duration of shoulder pain of the patients was not stated in the aforementioned study. The fact that the participants in our study had an average of six months of shoulder pain and that this condition contributed to the mechanisms of chronic pain may also explain the unresponsiveness to MTrP treatment in the subacute period. Indeed, MTrP is an entity that has the potential to become chronic regardless of the etiology and is easier to diagnose and treat in the acute phase.22
MTrP treatment using local anesthesia has similar effects as using DN and its effectiveness in reducing pain is independent of the injected drug.23 From this perspective, Liporaci FM et al. administered local anesthesia to MTrPs in HSP, and the results indicated that there was a decrease in pain intensity after treatment, while no change was observed at the end of the four-month follow-up.13 On the other hand, abduction measurements increased significantly. The disadvantage of this study was that conventional rehabilitation was not used in the treatment and there was no control group. In contrast, our study indicated predominance in the flexion and abduction movements compared to the control group at the end of the third month. Therefore, it can be concluded that MTrP treatment for HSP is more effective on improving joint range of motion when combined with conventional rehabilitation.