Botulinum toxin injections for shoulder and upper limb pain: a narrative review

Botulinum toxin for posterior shoulder instability unresponsive to conventional management

This case report describes the successful use of botulinum toxin A injections to treat persistent shoulder pain and instability in a middle-aged man with posterior labral tear and capsular laxity. Despite arthroscopic repair, the patient experienced recurring pain attributed to hypertonicity of the latissimus dorsi muscle. Botulinum toxin injection into the latissimus pars ascendens resulted in significant pain relief and improved function within 1 month. At 6 months, the patient had resumed normal activities pain-free. This innovative application of botulinum toxin beyond spasticity management effectively addressed residual muscular imbalance driving instability. It represents a novel therapeutic option for refractory shoulder pain and dysfunction. Further research is warranted to establish efficacy and safety, but this positive outcome highlights the potential to expand indications for botulinum toxin in musculoskeletal disorders with a hypertonicity component.

Influence of Apis mellifera syriaca Bee Venom on Nociception and Inflammatory Cytokine Profiles in Experimental Hyperalgesia

Hyperalgesia is a condition marked by an abnormal increase in pain sensitivity, often occurring in response to tissue injury, inflammation, or prolonged exposure to certain medications. Inflammatory mediators, such as cytokines IL-1β, IL-6, and TNF-α, play a central role in this process, amplifying pain perception. Developing effective treatments that address the underlying mechanisms of hyperalgesia is an active field of research. Apis mellifera syriaca venom demonstrated potential immunomodulatory activity associated with cytokine release in vivo. Therefore, the aim of this study is to evaluate the effect of Apis mellifera syriaca bee venom (AmsBV) on pain sensitivity in a formalin-induced hyperalgesia mice model and to evaluate the potential role of cytokines associated with the nociception of pain. The hotplate test, used to measure pain latency, showed that hypersensitivity to pain was induced in formalin-injected male mice only, with no changes in females, suggesting a sex-based response to formalin. When applied, AmsBV reduced pain sensitivity in males, suggesting pain relief potential. At the molecular level, AmsBV was able to reduce pro-inflammatory interleukin IL-4 and cytokine IFN-γ, emphasizing its immunomodulatory potential. Interestingly, the venom restored anti-inflammatory IL-10 levels that were significantly decreased in hyperalgesia males. Together, these findings highlight the therapeutic potential for AmsBV in managing inflammation and reducing pain, particularly hyperalgesia.

Effect of ultrasound-guided injection of botulinum toxin type A into shoulder joint cavity on shoulder pain in poststroke patients: study protocol for a randomized controlled trial

BACKGROUND

Hemiplegic shoulder pain (HSP) is a common complication after stroke. It severely affects the recovery of upper limb motor function. Early shoulder pain in hemiplegic patients is mainly neuropathic caused by central nerve injury or neuroplasticity. Commonly used corticosteroid injections in the shoulder joint can reduce shoulder pain; however, the side effects also include soft tissue degeneration or increased tendon fragility, and the long-term effects remain controversial. Botulinum toxin injections are relatively new and are thought to block the transmission of pain receptors in the shoulder joint cavity and inhibit the production of neuropathogenic substances to reduce neurogenic inflammation. Some studies suggest that the shoulder pain of hemiplegia after stroke is caused by changes in the central system related to shoulder joint pain, and persistent pain may induce the reorganization of the cortical sensory center or motor center. However, there is no conclusive evidence as to whether or not the amelioration of pain by botulinum toxin affects brain function. In previous studies of botulinum toxin versus glucocorticoids (triamcinolone acetonide injection) in the treatment of shoulder pain, there is a lack of observation of differences in changes in brain function. As the content of previous assessments of pain improvement was predominantly subjective, objective quantitative assessment indicators were lacking. Functional near-infrared imaging (fNIRS) can remedy this problem.

METHODS

This study protocol is designed for a double-blind, randomized controlled clinical trial of patients with post-stroke HSP without biceps longus tenosynovitis or acromion bursitis. Seventy-eight patients will be randomly assigned to either the botulinum toxin type A or glucocorticoid group. At baseline, patients in each group will receive shoulder cavity injections of either botulinum toxin or glucocorticoids and will be followed for 1 and 4 weeks. The primary outcome is change in shoulder pain on the visual analog scale (VAS). The secondary outcome is the assessment of changes in oxyhemoglobin levels in the corresponding brain regions by fNIRS imaging, shoulder flexion, external rotation range of motion, upper extremity Fugl-Meyer, and modified Ashworth score.

DISCUSSION

Ultrasound-guided botulinum toxin type A shoulder joint cavity injections may provide evidence of pain improvement in patients with HSP. The results of this trial are also help to analyze the correlation between changes in shoulder pain and changes in cerebral hemodynamics and shoulder joint motor function.

TRIAL REGISTRATION

Chinese clinical Trial Registry, ChiCTR2300070132. Registered 03 April 2023, https://www.chictr.org.cn/showproj.html?proj=193722 .

Onabotulinum toxin injections for shoulder and chest wall muscle pain in breast cancer survivors: retrospective study - preliminary report

OBJECTIVES

The primary objective of this retrospective review is to describe patient-reported improvement in muscular pain after initial treatment with onabotulinum toxin. A secondary objective was to determine other physiatry (physical medicine & rehabilitation (PM&R)) interventions ordered.

METHODS

Preliminary retrospective review of physiatry interventions for 47 patients referred by breast radiation oncology to PM&R at a tertiary referral-based academic cancer centre clinic from 1 January 2018 to 31 December 2021 for muscular shoulder/chest wall pain.

RESULTS

Patients were most commonly diagnosed with muscle spasm 27/47 (58%), lymphedema 21/47 (45%), myalgia/myofascial pain 16/47 (34%), radiation fibrosis 14/47 (30%), fatigue/deconditioning 13/47 (28%), neurological impairment 11/47 (23%) and joint pathology 3/47 (6%). The top three physiatric interventions were home exercise programme education (17/47, 36%), botulinum toxin injection (17/47, 36%) and physical or occupational therapy referral (15/47, 32%). Patients who had muscle spasms documented were more likely to have botulinum toxin recommended by physiatry (24/24) compared with those with questionable spasms (4/7) and those without spasms(0/16) (p=0.0005). 17/28 (60.7%) received botulinum toxin injection, and a total of 35 injections were performed during the study period. 94% (16/17) of patients who received botulinum toxin injection voiced improvement in pain after injection.

CONCLUSION

Botulinum toxin injections may play a role in the treatment of muscle spasm-related pain in breast cancer survivors. Additional blinded controlled research on the effectiveness of botulinum toxin injection after breast cancer treatment with spastic muscular shoulder/chest wall pain is needed.

Anatomical analysis of the motor endplate zones of the suprascapular nerve to the infraspinatus muscle and its clinical significance in managing pain disorder

Myofascial pain syndrome caused by myofascial trigger points is a musculoskeletal disorder commonly encountered in clinical practice. The infraspinatus muscle is the region most frequently involved in the myofascial pain syndrome in the scapular region. The characteristics of the myofascial trigger points are that they can be found constantly in the motor endplate zone. However, localizing myofascial trigger points within the motor endplate zone and establishing an accurate injection site of the infraspinatus muscle has been challenging because the anatomical position of the motor endplate zone of the infraspinatus muscle is yet to be described. Therefore, this cadaveric study aimed to scrutinize the motor endplate zone of the infraspinatus muscle, propose potential myofascial trigger points within the muscle, and recommend therapeutic injection sites. Twenty specimens of the infraspinatus muscle for nerve staining and 10 fresh frozen cadavers for evaluation of the injection were used in this study. The number of nerve branches penetrating the infraspinatus muscle and their entry locations were analyzed and photographed. Modified Sihler's staining was performed to examine the motor endplate regions of the infraspinatus muscle. The nerve entry points were mostly observed in the center of the muscle belly. The motor endplate was distributed equally throughout the infraspinatus muscle, but the motor endplate zone was primarily identified in the B area, which is approximately 20-40% proximal to the infraspinatus muscle. The second-most common occurrence of the motor endplate zone was observed in the center of the muscle. These detailed anatomical data would be very helpful in predicting potential pain sites and establishing safe and effective injection treatment using botulinum neurotoxin, steroids, or lidocaine to alleviate the pain disorder of the infraspinatus muscle.

Post Hoc Subgroup Analysis of the BCause Study Assessing the Effect of AbobotulinumtoxinA on Post-Stroke Shoulder Pain in Adults

Botulinum toxin type A is approved for the focal treatment of spasticity; however, the effectiveness of abobotulinumtoxinA (aboBoNT-A) in patients with shoulder pain who have set reduced pain as a treatment goal is understudied. In addition, some patients encounter delays in accessing treatment programs; therefore, the suitability of aboBoNT-A for pain reduction in this population requires investigation. These factors were assessed in aboBoNT-A-naive Brazilian patients in a post hoc analysis of data from BCause, an observational, multicenter, prospective study (NCT02390206). Patients (N = 49, n = 25 female; mean (standard deviation) age of 60.3 (9.1) years; median (range) time since onset of spasticity of 16.1 (0-193) months) received aboBoNT-A injections to shoulder muscles in one or two treatment cycles (n = 47). Using goal attainment scaling (GAS), most patients achieved their goal of shoulder pain reduction after one treatment cycle (72.1%; 95% confidence interval: 57.2-83.4%). Improvements in GAS T-score from baseline, clinically meaningful reductions in pain score at movement, and clinically meaningful increases in passive shoulder abduction angle further improved with repeated treatment more than 4 months later, despite treatment starting at a median of 16.1 months after the onset of spasticity. These findings support the further investigation of aboBoNT-A injections in chronic post-stroke shoulder pain.

Retrospective study of the clinical effect of incobotulinumtoxinA for the management of myofascial pain syndrome in refractory patients

The aim was to evaluate the effectiveness and safety of IncobotulinumtoxinA (IncoA) for the management of myofascial pain syndrome (MPS) in refractory patients. This single-center, observational, retrospective study includes 37 patients. The pain reduction was 4.7 points (95%CI: 5.6 to -3.8) from baseline to one-month post-injection (using a 10-point visual analogue scale). Only 18.9% experienced mild adverse events. In conclusion, IncoA is an effective and safe alternative for the treatment of MPS in refractory patients.