Thoracic outlet syndrome (TOS) is a rare anatomic condition caused by compression of neurovascular structures as they traverse the thoracic outlet. Depending on the primary structure affected by this spatial narrowing, patients present with one of three types of TOS—venous TOS (vTOS), arterial TOS (aTOS), or neurogenic TOS (nTOS). Compression of the subclavian vein, subclavian artery, or brachial plexus leads to a constellation of symptoms, including venous thrombosis, with associated discomfort and swelling; upper extremity ischemia; and chronic pain due to brachial plexopathy. Textbooks have often reported the prevalence of TOS in females more than men, but few data exist to elaborate on the diversity in outcomes and treatments offered to females.

Recent publications have identified the impact of sex on surgical outcomes. This has been investigated from the perspective of surgeon sex on selection, treatment, and outcome, and we have also seen how patient sex influences treatment selection and outcomes in several surgical fields [1]. There are also data indicating that sex differences exist in pain [2]. Few studies published on TOS have elaborated on sex differences in outcomes, compared surgical morbidity and mortality, or considered outcomes from physical therapy and nonsurgical management. Chang et al [3] discussed the impact of sex on complications in patients with nTOS undergoing first rib resection. They found that females experienced fewer vascular injuries than men, although, to our knowledge, no data exist regarding the resolution of symptoms or the need for further therapy [3]. In this review, we aimed to identify sex-based differences in the demographic characteristics of patients presenting with TOS, identify differences among who is offered surgical intervention, and look at sex differences in outcomes for TOS treatment.

Venous TOS, also known as Paget-Schroetter syndrome or effort thrombosis, is due to axillary or subclavian vein thrombosis in the thoracic outlet region, and makes up 3% to 5% of TOS presentations [4]. The axillosubclavian vein is compressed as it traverses the first rib, most often due to hypertrophy of the subclavius muscle anteriorly or anterior scalene muscle posteriorly or occasionally due to prior trauma, such a clavicle fracture. Primarily, subclavian-axillosubclavian vein thrombosis is due to the repetitive cycle of injury, inflammation, and recovery leading to perivenous fibrosis, endothelial injury, venous stenosis, and blood flow stasis [5,6]. A narrow costoclavicular space around the vein and repetitive arm movements induce this injury cycle. Treatment of vTOS includes anticoagulation and thrombolysis for acute thrombosis. To prevent recurrent thrombosis, surgical decompression with first rib resection is often recommended.

Arterial TOS is the rarest, representing 1% of the TOS population and 3% to 6% of patients undergoing first rib resection. The arterial sequelae of TOS are most commonly associated with bony abnormalities, such as cervical ribs with partial or complete fusion to the first rib by a bony pseudoarthrosis [7]. This compresses the subclavian artery, causing poststenotic dilatation that progresses to aneurysmal changes with associated thrombus and embolization. Early disease can also present as upper extremity claudication or unilateral Raynaud syndrome. Treatment primarily involves surgical decompression by means of resecting the cervical and first rib or other bony anomalies causing impingement [8]. Additional steps may also be needed to treat acute embolus, resect the aneurysm, and restore flow distally [9].

Neurogenic TOS is the most common and an often disputed type of TOS due to the complex nature of patients’ pain and vague symptomology. Patients often present with a longstanding history of unilateral pain, paresthesia, muscle atrophy, headache, or positional symptoms. However, 10% of patients can have bilateral symptoms due to repetitive neck or upper body strain [10]. No definitive diagnostic test or pathognomonic symptom defines nTOS, but certain diagnostic studies and therapies may be employed to determine whether a patient would benefit from surgical intervention. A trial of anterior muscle scalene block can help determine whether a patient would benefit from surgical decompression [11]. This emulates the relief that can be achieved through first rib resection and anterior scalenectomy and can help determine who should be offered surgery.