Identifying the exact cause for persistent and recurrent neurogenic thoracic outlet syndrome (NTOS) is challenging even with high-resolution imaging of the thoracic outlet. Improvement can be achieved with redo first rib resection, although the posterior first rib remnant is one of several potential points of brachial plexus compression. In approaching reoperative surgery for NTOS, the aim is to provide complete thoracic outlet decompression as guided by the patient’s history, physical examination, and adjunctive imaging. This may involve resection of the posterior first rib remnant, scar tissue encasing the brachial plexus, elongated C7 transverse process, cervical rib, and/or pectoralis minor tendon.
Key points
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There are no prospective, randomized trials evaluating the surgical treatment for persistent or recurrent neurogenic thoracic outlet syndrome (NTOS). Retrospective studies suggest that an inadequately resected posterior first rib is the primary cause for persistent or recurrent NTOS.
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Reoperative surgery for persistent or recurrent NTOS involves resection of the unaddressed anatomic points of brachial plexus compression (posterior first rib remnant, scalene musculature, cervical rib, elongated C7 transverse process, and/or pectoralis minor tendon) as guided by the patient’s history, physical examination, and adjunctive imaging.
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Although studies investigating reoperative surgery for persistent or recurrent NTOS vary significantly in total number of patients and the operation performed, most reports indicate that approximately 50% of patients demonstrate significant improvement following reoperation.
Introduction
Thoracic outlet syndrome (TOS) is a disorder characterized by compression of the neurovascular structures traversing the thoracic outlet. The 3 subtypes of TOS, neurogenic (NTOS), arterial (ATOS), and venous TOS (VTOS), are categorized according to signs and symptoms related to compression of the brachial plexus, subclavian artery, or subclavian vein. The incidence of TOS in the population is estimated between 0.3% and 2% and most commonly presents between the ages of 20 and 40 years with increased prevalence in women. NTOS represents most cases (∼90%) with fewer number of patients diagnosed with VTOS (∼10%) or ATOS (<1%).
Nature of the problem
Neurovascular compression is thought to occur in the interscalene triangle, costoclavicular space, or retropectoralis minor space ( Fig. 1 ). In contrast to VTOS and ATOS wherein the diagnosis can be established via angiography, the diagnosis of NTOS relies on patient symptomatology alone as there is no definitive clinical examination, test, or imaging modality to confirm the condition. Furthermore, there are numerous musculoskeletal disorders of the upper extremity, shoulder, and cervical spine that can present with pain, neuropathy, and weakness with similar distribution to NTOS. Previously, the terms “disputed” or “nonspecific” NTOS were used to describe patients presenting with neurogenic symptoms consistent with brachial plexus compression without classic nerve conduction abnormalities. These terms have fallen out of favor, although the diagnostic challenges remain.
Nonsurgical management for patients with NTOS is multimodal involving physical therapy, ergonomic considerations, pain management, lifestyle modification to avoid activities that exacerbate symptoms, and anesthetic injections into the scalene and/or pectoralis minor muscles. One of the few prospective, randomized clinical trials for the treatment of TOS examined symptomatic response in patients (n = 38) receiving botulinum toxin (BTX) injection into the scalene muscles compared with those receiving placebo injection of saline. Despite many retrospective reviews suggesting symptomatic improvement with such treatment, the trial found no significant difference in pain, disability, or paresthesias in patients receiving BTX compared with placebo. The generalizability of these findings are limited, however, as outcomes were not stratified by neurogenic or vascular TOS and alternative anesthetic agents or injection sites such as the pectoralis minor muscle were not investigated. An estimated 30% of patients with NTOS symptoms fail conservative management and undergo surgical intervention. The standard operation for NTOS is first rib resection (FRR), anterior and middle scalenectomy, and brachial plexus neurolysis with success rates ranging from 64% – 71% following initial surgical intervention.
If they occur, recurrent NTOS symptoms typically develop within 12 to 18 months of surgical intervention. Recurrent symptoms occur with increased frequency in patients with older age (>40 years), longer duration of preoperative symptoms, active smoking, and chronic pain syndromes. In addition, lack of preoperative symptomatic relief following local anesthetic injection into the anterior scalene or pectoralis minor has been correlated with surgical failure. An inadequately resected first rib is widely cited as the primary technical failure for persistent or recurrent brachial plexus compression. Residual anterior or middle scalene musculature, bony abnormalities (cervical rib and elongated C7 transverse process), and the pectoralis minor tendon have also been implicated. This article focuses on the diagnosis, reoperative surgical management, and clinical outcomes for patients with persistent or recurrent NTOS.
Patient evaluation overview
NTOS remains a clinical diagnosis of exclusion, which makes a thorough history and physical examination critical in patients presenting with concern for persistent or recurrent NTOS following prior surgical treatment. Persistent NTOS is defined as no improvement following surgical treatment. Recurrent NTOS describes patients that have experienced at least 3 months of improvement following the index operation with subsequent return of symptoms. The Society for Vascular Surgery (SVS) has established both diagnostic criteria for NTOS and reporting standards for patients with suspected persistent or recurrent NTOS after surgical treatment ( Table 1 ). According to the SVS guidelines, 3 of the following 4 criteria must be present for the diagnosis of NTOS: (1) symptoms related to inflammation of the scalene triangle that are reproducible with palpation of the scalene musculature; (2) arm or hand pain, paresthesias, and/or weakness compatible with central nerve compression that are reproducible on physical examination; (3) absence of confounding diagnoses including regional pain syndrome and disorders of the shoulder, cervical spine, or carpal tunnel; (4) clinical improvement with scalene muscle injection.
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In evaluating a patient with concern for persistent or recurrent NTOS, attention should be given to prior TOS operations performed and initial therapeutic response as well as coexisting musculoskeletal disorders of the upper extremity and cervical spine. If symptoms initially improved and then recurred, the duration of improvement and events leading to symptom recurrence should be detailed. The current level of global TOS disability should be assessed, specifically eliciting exacerbating activities or movements and the distribution of pain, paresthesias, and/or weakness. A thorough neurovascular examination of the upper extremity should be performed including assessment for Tinel signs, wherein gentle percussion overlying the brachial plexus, cubital tunnel, or carpel tunnel induces paresthesias in the underlying nerve’s distribution. The patient should be examined for tenderness overlying the interscalene triangle, costoclavicular space, and just below the coracoid process (pectoralis minor insertion point), which may help to localize the unaddressed anatomic point of brachial plexus compression. Patient response to provocative testing including positioning the arm at 90° of abduction with external rotation and an upper extremity tension test should be recorded.
To evaluate the bony architecture and aberrant anatomy including an ipsilateral cervical rib or elongated C7 transverse process, chest and cervical spine radiographs are routinely obtained. Though not required for diagnosis, electromyographic (EMG) testing and detailed imaging of the brachial plexus can be pursued. As it pertains to EMG testing, medial antebrachial cutaneous nerve measurements showing increased latency and decreased amplitude have been associated with the diagnosis of NTOS, although the overwhelming majority of patients with NTOS symptoms will have normal electrodiagnostic results. ,
In our practice, a multiphase contrast enhanced computed tomography angiography (CTA) of the thoracic outlet is obtained for all patients presenting with persistent or recurrent TOS after surgical treatment. A magnetic resonance angiography is an alternative imaging modality for detailed anatomic information, although detailed visualization of the first rib remnant is limited. The CTA of the thoracic outlet allows for a detailed anatomic assessment of prior surgical intervention with attention given to residual anterior and middle scalene musculature, length of remnant posterior rib relative to the T1 transverse process, bone ossification, and unresected cervical rib or elongated C7 transverse process ( Fig. 2 ). Though not validated, a potential surrogate marker for brachial plexus compression in either the interscalene triangle or retropectoralis minor space is extrinsic compression of the subclavian artery within these anatomic regions.
