The purpose of this study is:

1. To assess the effect of BOTOX injection to the scalene muscles on the severity of pain from TOS.
2. To assess the effect of BOTOX injection on numbness and tingling and quality of life.

Background:

Thoracic Outlet Syndrome (TOS) is a symptom complex consisting of pain, paresthesias and often functional impairment caused by compression of the neurovascular supply to the upper limb. Impingement may occur at the interscalene triangle, and both anesthetic blockade and chemodenervation of the scalene muscles have been shown to temporarily improve symptoms of TOS in non-randomized controlled trials.

Objective:

To assess the effect of Botulinum Toxin Type A (BTX-A) injections into the scalene muscles on pain, paresthesias and function in subjects with TOS.

Hypothesis:

BTX-A injected into the anterior and middle scalene muscles will reduce the irritation on the neurovascular structures at the interscalene triangle in subjects with TOS. This will lead to reductions in pain and paresthesias, and improvements in function when compared with injection of placebo.

Intervention:

Each subject will receive an injection under EMG guidance into the anterior and middle scalene muscles of either 75 units of BTX-A (experimental group), or normal saline (control group). Both groups will be provided with a stretching and strengthening exercise program.

Inclusion Criteria:

• Age at least 19 years
• Medically stable
• Able to give informed consent
• Meets criteria for clinical diagnosis of TOS
• Symptoms of TOS present for at least six months
• Have had EMG studies and a CT or MRI scan of the cervical spine

Exclusion Criteria:

• Prior treatment with BTX-A
• Allergy to BTX-A
• History of botulinum toxicity
• Prior scalenectomy
• Surgery for TOS planned within six months
• Use of blood thinners, i.e., warfarin; unfractionated or low molecular weight heparin
• History of Myasthenia Gravis, Eaton-Lambert Syndrome or Shy-Drager Syndrome
• Unable to complete follow-up assessments at 6 weeks, 3 months and 6 months
• Any abnormalities on EMG, CT or MRI studies suggesting an alternate diagnosis
• Pregnancy or planned pregnancy within six months