Thoracic outlet syndrome: A neurological and vascular disorder

Abstract

Thoracic outlet syndrome (TOS) is a condition arising from compression of the subclavian vessels and/or brachial plexus as the structures travel from the thoracic outlet to the axilla. Despite the significant pathology associated with TOS, there remains some general disagreement among experts on the specific anatomy, etiology, and pathophysiology of the condition, presumably because of the wide variation in symptoms that manifest in presenting patients, and because of lack of a definitive gold standard for diagnosis. Symptoms associated with TOS have traditionally been divided into vascular and neurogenic categories, a distinction based on the underlying structure(s) implicated. Of the two, neurogenic TOS (nTOS) is more common, and typically presents as compression of the brachial plexus; primarily, but not exclusively, involving its lower trunk. Vascular TOS (vTOS) usually involves compression of the vessel, most commonly the subclavian artery or vein, or is secondary to thrombus formation in the venous vasculature. Any anatomical anomaly in the thoracic outlet has the potential to predispose a patient to TOS. Common anomalies include variations in the insertion of the anterior scalene muscle (ASM) or scalenus minimus muscle, the presence of a cervical rib or of fibrous and muscular bands, variations in insertion of pectoralis minor, and the presence of neurovascular structures, which follow an atypical course. A common diagnostic technique for vTOS is duplex imaging, which has generally replaced more invasive angiographic techniques. In cases of suspected nTOS, electrophysiological nerve studies and ASM blocks provide guidance when screening for patients likely to benefit from surgical decompression of TOS. Surgeons generally agree that the transaxillary approach allows the greatest field of view for first rib excision to relieve compressed vessels. Alternatively, a supraclavicular approach is favored for scalenotomies when the ASM impinges on surrounding structures. A combined supraclavicular and infraclavicular approach is preferred when a larger field of view is required. The future of TOS management must emphasize the improvement of available diagnostic and treatment techniques, and the development of a consensus gold standard for diagnosis. Helical computed tomography offers a three-dimensional view of the thoracic outlet, and may be valuable in the detection of anatomical variations, which may predispose patients to TOS. This review summarizes the history of TOS, the pertinent clinical and anatomical presentations of TOS, and the commonly used diagnostic and treatment techniques for the condition.

Thoracic outlet syndrome: clinical and diagnostic features

“…Классификация и эпидемиология синдрома верхней апертуры грудной клетки Предложены разные классификации TOS, из ко-торых самой популярной является разделение синдро-ма в зависимости от преимущественного вовлечения в процесс структур, входящих в верхнюю апертуру [8,9,14,15], на основании чего выделяют 4 основных варианта: артериальный, венозный, нейрогенный и смешанный сосудисто-нейрогенный (табл. 1).…”

“…В 95 % всех случаев TOS наблюдается нейроген-ный вариант, в 3 % -венозный и лишь в 1 % -арте-риальный [8,11,15,17]. В составе нейрогенного на до-лю случаев истинного TOS приходится всего 1 %, распространенность которого составляет 1:1 000 000, частота спорного TOS достигает 80:1000 [7,8,17], при-чем чаще патология встречается у женщин в возрасте 20-40 лет [17].…”

“…Причин для обоснованных разногласий много. Во-первых, неоднозначная и запутанная история развития представлений об этом синдроме [15]. Во-вторых, неоднозначный термин используется для объедине-ния поражений как нервов, так и сосудов.…”

Cervical Rib and Thoracic Outlet Syndrome

“…Vascular TOS (vTOS) primarily involves compression of the subclavian artery or vein, or it is sometimes secondary to thrombus formation in the venous vasculature. Anatomical anomalies in the thoracic outlet has the potential to predispose to any of the types of the TOS like variable insertions of scalenus anterior, scalenus minimus or pectoralis mino muscle, cervical rib, fibrous and muscular bands, and atypical course of neurovascular structures of the outlet [24].…”

Neurogenic thoracic outlet syndrome: current diagnostic criteria and advances in MRI diagnostics

“…Compression can occur between the anterior and middle scalene muscles, underneath a cervical rib, beneath the pectoralis minor tendon, or by fibrous bands anywhere along the course of the plexus. 11 The most common symptoms, including pain in the neck, shoulder, arm, and hand, are typically unilateral but can also occur bilaterally. 13 In one of the largest studies of nTOS, symptoms of lower plexus compression were most common (68%), followed by symptoms of both upper and lower plexus compression (20%) and symptoms of upper plexus compression alone (12%).…”