Abstract
Structural variations of the thoracic outlet create a unique risk for neurogenic thoracic outlet syndrome (nTOS) that is difficult to diagnose clinically. Common anatomical variations in brachial plexus (BP) branching were recently discovered in which portions of the proximal plexus pierce the anterior scalene. This results in possible impingement of BP nerves within the muscle belly and, therefore, predisposition for nTOS. We hypothesized that some cases of disputed nTOS result from these BP branching variants. We tested the association between BP piercing and nTOS symptoms, and evaluated the capability of ultrasonographic identification of patients with clinically relevant variations. Eighty-two cadaveric necks were first dissected to assess BP variation frequency. In 62.1%, C5, superior trunk, or superior + middle trunks pierced the anterior scalene. Subsequently, 22 student subjects underwent screening with detailed questionnaires, provocative tests, and BP ultrasonography. Twenty-one percent demonstrated atypical BP branching anatomy on ultrasound; of these, 50% reported symptoms consistent with nTOS, significantly higher than subjects with classic BP anatomy (14%). This group, categorized as a typical TOS, would be missed by provocative testing alone. The addition of ultrasonography to nTOS diagnosis, especially for patients with BP branching variation, would allow clinicians to visualize and identify atypical patient anatomy.
Highlights
Neurogenic thoracic outlet syndrome is a neurologic impingement syndrome that is notoriously difficult to diagnose in the clinical setting [1,2]
The variant anatomy occurred more frequently in male cadavers than in females (74.5% vs. 56.8%); the t-test indicated that these differences between the sexes did not reach the statistical threshold for significance (t = −1.83, p = 0.07)
For patients with one of the piercing variations, we propose a rational plan of osteopathic manipulative treatment (OMT) care and/or physical therapy consisting of indirect treatment modalities and the avoidance of direct techniques, based upon the potential for further impingement of the nerve within the muscle belly
Summary
Neurogenic thoracic outlet syndrome (nTOS) is a neurologic impingement syndrome that is notoriously difficult to diagnose in the clinical setting [1,2]. Adson’s [4], Wright’s, and Costoclavicular tests utilize the classic relationship of the subclavian artery and the branches of the brachial plexus to identify specific sites of neurovascular impingement (Table 1). These tests diagnose compression at three distinct sites: within the interscalene space, deep to the pectoralis minor tendon, and between the first rib and clavicle. Adson’s test evaluates the passage of the brachial plexus trunks and subclavian artery as they pass through the interscalene space between the anterior and Diagnostics 2017, 7, 40; doi:10.3390/diagnostics7030040 www.mdpi.com/journal/diagnostics
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