Abstract
Thoracic outlet syndrome (TOS) is a group of disorders caused by compression of neurovascular structures in the thoracic outlet, presenting with arm pain, paresthesia, and muscle weakness. Peripheral nerve blocks of the anterior scalene and pectoralis minor muscles are traditionally performed by radiologists and pain specialists for diagnosis. This study evaluates the efficacy of surgeon-performed nerve blocks in diagnosing and treating TOS. We conducted a retrospective chart review for patients receiving ultrasound-guided nerve blocks performed by a vascular surgeon from 2022 to 2023. Among 87 patients, 72.4% were diagnosed with neurogenic TOS, and surgical interventions were performed in 46 (52.9%) patients. Of these, 71.7% reported symptom improvement postoperatively. Ultrasound-guided peripheral nerve blocks performed by vascular surgeons offer an efficient way to work up neurogenic TOS and identify patients who may obtain prolonged symptomatic improvement following vascular surgery.
Thoracic outlet syndrome (TOS) refers to a group of disorders characterized by the compression of neurovascular structures traversing the thoracic outlet and are characterized as arterial (ATOS), venous TOS (VTOS), or, most commonly, neurogenic (NTOS). 1 The thoracic outlet is an anatomically defined space, delineated by the clavicle, first rib, and anterior scalene muscle, which harbors vital structures such as the brachial plexus and subclavian vessels. The compressions in TOS are often due to anatomical abnormalities, such as a cervical rib, inflammation following trauma or repetitive stress, and scalene muscle hypertonicity. 2 Common clinical manifestations of NTOS include radiating arm and hand pain, paresthesia, weakness, and upper extremity muscle atrophy. Compression of the subclavian vessels results in VTOS and ATOS, and can present with arterial insufficiency, pallor, coldness, digital ischemia, and upper extremity pain and swelling.
The diagnosis of TOS is primarily made through clinical suspicion and physical examination findings. The clinical presentations of TOS have wide overlap with other neuropathic or musculoskeletal disorders, and physical examination has low specificity. 2 Studies have demonstrated the efficacy of injecting local anesthetics into either the scalene muscles or the pectoralis minor to support or rule out TOS based on the presence of temporary symptomatic relief following the neuromuscular blockage. 3 Diagnosing TOS through nerve blocks has typically relied on multidisciplinary teams involving radiologists, pain anesthetists, orthopedic surgeons, and physiotherapists. 2 The reliance on coordinating multidisciplinary care teams for the diagnosis of TOS increases the risk of loss of follow-up and significant delays in diagnosis, resulting in increased morbidity and healthcare-related costs.
In this study, we describe the diagnosis and treatment of TOS using peripheral nerve blocks performed solely by vascular surgeons. Retrospective medical record review was performed under an institutional review board-exempt protocol. We included patients ≥18 years of age who underwent an ultrasound-guided peripheral nerve block of either the anterior scalene muscle (Figure 1) or the pectoralis minor muscle (Figure 2). Nerve blocks were performed by a vascular surgeon at a single, large tertiary referral center from 2022 to 2023. Positive nerve block test results were defined as a temporary improvement or complete resolution of patient-reported symptoms within under 24 hours following injection of the local anesthetic. All patients with a positive nerve block were offered follow-up surgical consultation. Patient-reported changes in symptoms were reported from their first and most recent follow-up appointments. Eighty-seven patients who received peripheral nerve blocks were included in this study. Ultrasound image of middle scalene (left, red) and anterior scalene (right, red) muscles and the brachial plexus (yellow). Anesthetic is injected into the anterior scalene muscle, as depicted by the white line. Ultrasound image of the pectoralis minor (red) muscle. Anesthetic is injected into the pectoralis minor muscle, as depicted by the white line.
The study population had a median age of 38 years (IQR, 26-47) and a median BMI of 27.6. Of the patients, 65.5% (n = 57) were female, and 75.9% (n = 66) identified as white. Tobacco use was reported by 5 patients (5.7%). A total of 65 (74.7%) patients had a diagnosis of TOS, with 63 (72.4%) having a diagnosis of NTOS, 2 (2.3%) with VTOS, and no patients with arterial TOS. Of the 65 patients with a diagnosis of TOS through peripheral nerve block, NTOS comprised 96.9%. The right arm was affected in 60.9% of patients. Following nerve block, 52.9% of patients had a surgical intervention. Of the 46 (52.9%) patients who underwent surgery, 33 (71.7%) reported improvement or resolution of their symptoms at their first postoperative follow-up.
Demographics and Procedural Details.
n (%) or median (IQR).
Statistical significance noted by *P < 0.05, **P < 0.01, and ***P < 0.001.
Abbreviations: TOS, thoracic outlet syndrome, BMI, body mass index, IQR, interquartile range.
Diagnosing TOS is inherently challenging due to its complex clinical presentation and overlapping symptoms with other neuromuscular conditions and the lack of any gold standard diagnostic test. The heterogeneity of TOS subtypes further complicates diagnosis, as each subtype presents with distinct and often subtle signs. 2 With no universally accepted diagnostic test for TOS, many clinicians rely on a combination of clinical examination, imaging, and symptom provocation tests, which can yield variable sensitivity and specificity. 2 This diagnostic inefficiency can result in delayed or complete misdiagnosis leading to an increased financial burden and psychosocial stress on patients.
Peripheral nerve blocks have emerged as a promising, cost-effective diagnostic modality for NTOS. These blocks offer relatively high sensitivity, providing valuable diagnostic clarity, particularly in cases where physical examination findings are equivocal or non-specific. 4 Given the lack of universally accepted and highly sensitive physical examination tests for TOS, peripheral nerve blocks present an opportunity to streamline the diagnostic process and reduce delays. 1 Increasing awareness and utilization of peripheral nerve blocks among physicians could expedite appropriate referrals and timely initiation of treatment, ultimately mitigating the clinical and economic burden associated with delayed diagnosis. 4
Vascular surgeons who are trained to perform scalene muscle and pectoralis minor blocks are uniquely positioned to streamline the diagnosis-to-treatment pathway for TOS. Historically, these blocks have been administered predominantly by nonsurgical specialists, who are often unable to provide definitive treatment, necessitating further referral following a positive diagnostic test. 3 By integrating these diagnostic blocks into their practice, vascular surgeons can expedite the process from initial diagnosis to therapeutic intervention, reducing delays and improving patient outcomes.
The limited data on diagnostic and treatment efficacy for vascular TOS subtypes are primarily attributable to their lower prevalence and the more complex diagnostic methods required, such as duplex ultrasonography, arteriography, and sometimes venography. Vascular surgeons are often best equipped to perform and interpret these advanced diagnostic modalities, making early referral to such specialists critical in the workup of suspected TOS. Enhancing access to vascular surgeons for both diagnostic and therapeutic care may reduce inefficiencies in management, particularly for rarer subtypes like VTOS, and further improve outcomes across the spectrum of TOS presentations.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
