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Efficacy of Scalene Muscle Botulinum Toxin Injection for the Treatment of Neurogenic Thoracic Outlet Syndrome

10 August 2013


Background: Neurogenic thoracic outlet syndrome (nTOS) is a disease process caused by the compression of neurovascular structures passing through the anatomical thoracic outlet. This compression can manifest as pain, paresthesia, progressive muscle weakness and subsequent muscle loss of the effected limb. Current mainstay treatment for patients with nTOS is conservative therapy and surgical decompression. However, in recent years, botulinum toxin, which is a neuromuscular junction blocking agent has been effective as a short-term treatment.

Method: A literature search using the following search engines CINAHL, MEDLINE-OVID, EBMR Multifile and Web of Science was conducted using the following search terms: thoracic outlet syndrome, botulinum toxin and Botox. Inclusion criteria were: adults diagnosed with thoracic outlet syndrome who were being treated with botulinum toxin injections alone, studies in English, dates from 2000-2012. Studies excluded if patients had previous surgical intervention for TOS and evaluated using the GRADE system.

Results: Three studies met inclusion criteria. A double-blind, randomized, controlled trial involving 38 patients used ultrasound-guided Botox injections in the scalene and pectoralis minor muscles for treatment of patients with nTOS. Results showed no clinical difference in treatment and placebo groups when compared on a visual analog scale. A prospective longitudinal study involving 27 patients receiving CT-guided low dose Botox injections to the anterior scalene muscle, resulted in as much as 47% reduction in pain. Lastly, a prospective study that enrolled 22 subjects examined nTOS patients response to electrophysiologically and fluoroscopically guided Botox injections in the anterior scalene, middle scalene and pectoralis minor muscles, demonstrated a greater than 50% reduction of pain in 64% of the cohort.

Conclusion: Two quasi-experimental studies demonstrated Botox injections in the scalene muscles and pectoralis minor muscle to be effective in symptomatic treatment of nTOS but results of a recent randomized controlled trial show no clinical significance. All relevant articles revealed limitations, with each of the studies needing a larger sample size, better randomization, blinding techniques and a more specific and well defined inclusion criteria.


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