A double-blind, controlled, randomized trial to evaluate the efficacy of botulinum toxin for the treatment of lumbar myofascial pain in humans. Efficacy and safety of a single botulinum type A toxin complex treatment (Dysport) for the relief of upper back myofascial pain syndrome: results from a randomized double-blind placebo-controlled multicentre study. The effect of small doses of botulinum toxin a on neck-shoulder myofascial pain syndrome: a double-blind, randomized, and controlled crossover trial. A double-blind, controlled study of botulinum toxin A in chronic myofascial pain.
Among all the causes of chronic low back pain, myofascial pain syndrome of the spinal stabilizer muscles is one of the most frequent, yet underconsidered sources of pain. The purpose of this prospective, randomized, double-blind, controlled trial was to evaluate the efficacy of type-A botulinum toxin (BTX-A) in relieving myofascial pain in patients experiencing mechanical low back pain due to bilateral myofascial pain syndrome involving the iliopsoas and/or the quadratus lumborum muscles.
                Each of the 27 enrolled patients received a bilateral, fluoroscopically guided injection in the affected muscle(s) to randomly deliver BTX-A in one side of the low back and a control drug (randomly constituted by NaCl 0.9% or bupivacaine 0.25%) in the opposite side. To evaluate the effects of treatment on daily life activities and psychologic status, 5 different questionnaires were administered (Hospital Anxiety and Depression scale [HAD-A and HAD-D], Lattinen, Oswestry, and Spielberger State-Trait Anxiety Index).
                BTX-A injection did not significantly reduce visual analog scale scores more than treatment with NaCl or bupivacaine in the contralateral side; furthermore, the treatments administered did not result in a significant improvement of patients' daily life activities or psychologic status. Although a trend toward a decrease in postintervention visual analog scale scores could be recognized in all low back sides, this trend was significant only in the sides treated with BTX-A.
                BTX-A seems to provide significant postintervention pain relief. However, considering its high cost and the small differences compared with control treatments, its use should be reserved only for patients with pain refractory to other invasive treatments. Botulinum type A toxin (BoNT-A) has antinociceptive and muscle-relaxant properties and may help relieve the symptoms of myofascial pain syndrome. In this study we evaluated the efficacy and tolerability of BoNT-A (Dysport) in patients with myofascial pain syndrome of the upper back. We conducted a prospective, randomized, double-blind, placebo-controlled, 12-week, multicentre study. Patients with moderate-to-severe myofascial pain syndrome affecting cervical and/or shoulder muscles (10 trigger points, disease duration 6-24 months) were randomized to Dysport or saline. Injections were made into the 10 most tender trigger points (40 units per site). The primary outcome was the proportion of patients with mild or no pain at week 5. Secondary outcomes included changes in pain intensity and the number of pain-free days per week. Tolerability and safety were also assessed. At week 5, significantly more patients in the Dysport group reported mild or no pain (51%), compared with the patients in the placebo group (26%; p=0.002). Compared with placebo, Dysport resulted in a significantly greater change from baseline in pain intensity during weeks 5-8 (p<0.05), and significantly fewer days per week without pain between weeks 5 and 12 (p=0.036). Treatment was well tolerated, with most side effects resolving within 8 weeks. In conclusion, in patients with upper back myofascial pain syndrome, injections of 400 Ipsen units of Dysport at 10 individualised trigger points significantly improved pain levels 4-6 weeks after treatment. Injections were well tolerated. Myofascial pain syndrome is a common cause of muscular pain in the shoulder-neck region. Injections of large amounts of botulinum toxin A have been found to be beneficial for the alleviation of myofascial pain, but large doses of this toxin may cause paresis of the muscle and other adverse events. The aim of this work was to determine the effect of small doses (5 U) of botulinum toxin A (BTA) injected directly into the painful trigger points of the muscles, using a double-blind crossover technique.
                On the basis of the empirical criteria proposed for diagnosis of myofascial pain syndrome, 31 patients suffering from myofascial pain in the neck-shoulder region were studied. The patients received either botulinum toxin A or physiological saline injections on 2 occasions 4 weeks apart. The total dose varied from 15 to 35 U of botulinum toxin A [28+/- 6 U (mean+/- SD)]. The follow-up measurements were carried out at 4 weeks after each treatment. Neck pain and result of treatment were assessed with questionnaires. The pressure pain threshold was determined using a dolorimeter.
                Neck pain values decreased from 4.3+/- 2.4 to 3.3+/- 2.0 after saline injections and from 4.1+/- 2.1 to 3.3+/- 2.2 after botulinum toxin A. The pressure pain threshold values increased from 5.2+/-1.6 to 5.9+/-1.5 and from 5.7+/-1.6 to 5.9+/-1.6 after injections with saline and botulinum toxin A, respectively. No statistically significant changes in the neck pain and pressure pain threshold values occurred between the botulinum toxin A and saline groups. After the first injections, the subjective result of treatment was significantly (P=0.008) in favor of botulinum toxin A, and after the second injections, the subjective result was better for saline, but the difference was not statistically significant (P=0.098). There was no significant difference in the prevalence of side effects between saline and botulinum toxin A.
                Our study shows that there was no difference between the effect of small doses of botulinum toxin A and those of physiological saline in the treatment of myofascial pain syndrome. Recent studies have reported a potential analgesic effect of botulinum toxin A (BTXA) in musculoskeletal pain. The present double-blind, randomized, placebo-controlled, parallel clinical trial studied the effect of BTXA on pain from muscle trigger points and on EMG activity at rest and during voluntary contraction.
                Thirty patients with trigger points in the infraspinatus muscles received either 50 units/0.25 mL of BTXA or 0.25 mL of isotonic saline. Baseline measures were determined during a run-in period of 1 week. Outcome measures including local and referred spontaneous pain, pain detection and tolerance thresholds to mechanical pressure, and shoulder movement were assessed at 3 and 28 days after injection. The interference pattern of the EMG during maximal voluntary effort of infraspinatus muscle was recorded and a standardized search for spontaneous electrical motor endplate activity at the trigger points was performed before and 28 days after BTXA or saline injection.
                BTXA reduced motor endplate activity and the interference pattern of EMG significantly but had no effect on either pain (spontaneous or referred) or pain thresholds compared with isotonic saline.
                The results do not support a specific antinociceptive and analgesic effect of botulinum toxin A.
There is inconclusive evidence to support the use of botulinum toxin in the treatment of MPS based on data from four studies with a total of 233 participants, which we considered adequate to be included in this review. Meta-analyses were not possible due to the heterogeneity between studies. We suggest that in future studies the same methodology to assess pain, a standardised dose of treatment, follow-up of at least four months (to observe the maximum/minimum curve of the drug effect) and appropriate data presentation should be used. More high-quality RCTs of botulinum toxin for treating MPS need to be conducted before firm conclusions on its effectiveness and safety can be drawn.