Role of Botulinum Toxin in Pectoralis Minor Syndrome

Background: Thoracic outlet syndrome (TOS) causes neurogenic symptoms in 95% of the cases due to neurovascular bundle compression. The treatment goal is the decompression of the neurovascular structures. In the last decade, non-surgical treatments have been evaluated as a treatment option for spastic syndromes and thoracic outlet syndrome. In this study we report the use of botulinum toxin (BTX-A) injection as a diagnostic tool to identify the pectoral minor syndrome, and as a less aggressive treatment-option. Methods: An observational cohort study of patients with neurogenic thoracic outlet syndrome who underwent sonographically guided chemodenervation of pectoral minor muscle with botulinum toxin. Follow-up includes clinical evaluation at one month, 3 months and 6 months after the procedure. Clinical evaluation was made with clinical questionnaire. In case of patients with partial improvement of the symptoms, a second infiltration of BTX-A was performed. The categorical variables were shown as percentages, and the continuous variables as mean and standard deviation (SD). For the comparison of categorical variables, the Fisher's exact test was used. Statistical analysis was performed using the SPSS version 20.0 program. We consider P <0.05 to be statistically significant. Results: A total of twenty-six patients were diagnosed with thoracic outlet syndrome in this period, and 20 accomplished the inclusion criteria. 7 patients were excluded (1 due to neoplasia, 2 did not sign the informed consent, 1 due to neoplasia, 2 did not sign the informed consent, 1 was lost during the follow-up and 3 due to anomalies of the first rib secondary to fractures and cervical rib and 1 was lost during the follow-up), therefore a sample of 13 patients aged between 24 and 55 years was obtained. The most common type of procedure performed was the single injection of 50 IU of botulinum toxin. 4 patients were infiltrated in 2 occasions due to partial improvement in symptoms at 1month follow-up. Clinical stability was found at three months and at 6 months follow-up. Conclusion: The ultrasound-guided botulinum injection of the pectoralis minor muscles provides symptoms relief in patients with pectoral minor syndrome, and could be considered a safe tool in the diagnosis of the pectoralis minor syndrome within the spectrum of thoracic operculum syndrome.