Conventionally TOS has been thought to represent a group of diverse disorders that result in compression of the neurovascular bundle exiting the thoracic outlet. Until recently, TOS classification has been based on symptoms, rather than the underlying pathology, with the subgroups consisting of neurogenic (NTOS), venous (VTOS or PSS), and arterial (ATOS). Neurogenic TOS accounts for over 95% of the cases, followed by venous (3–5%) and arterial (1–2%). Neurogenic TOS (NTOS) has been further divided into True NTOS (TNTOS) and Disputed NTOS (DNTOS), with DNTOS reportedly representing 95–99% of all neurogenic cases. In order to decrease confusion and to improve therapeutic results with TOS, the disease should be classified based on the underlying pathologic entity. Acquired and traumatic abnormalities of the clavicle and first rib should be classified separately. Clearly after the more common and objectively supported diagnoses of conditions that result in neurovascular symptoms of the upper extremity, such as cervical spine disease, carpal tunnel disease, and nerve entrapment syndromes, have been ruled out, there remains a group of patients who are suspected of having TOS. In these patients, rather than the more usual classification such as arterial, venous, or neurogenic, the more accurate approach from a diagnostic and therapeutic approach is to classify them as: Cervical Rib Disease: Patients with cervical rib syndrome (CRS) can have complications relating to compression of the subclavian artery (previously referred to as ATOS) and the brachial plexus(previously referred to as True NTOS) secondary to a well-formed cervical rib, or to an incompletely formed first rib, fibrous band associated with a rudimentary cervical rib, or a giant transverse process of C7. Thoracic Outlet Disease or “Subclavian Vein Compression Syndrome”: In these patients an abnormal first rib at its junction with the sternum results in compression of the subclavian vein at the subclavian-innominate junction. Compression of the vein results in venous hypertension in the upper extremity and resultant neurologic symptoms. With prolonged compression of the subclavian-innominate junction, the vein clots giving rise to Paget–Schroetter syndrome. Therefore, patients who have been previously classified as Disputed Neurogenic and Venous TOS represent a variable symptomatic presentation of the same pathologic entity, which affects the subclavian vein. Presently MRA of the thoracic outlet with arm maneuvers is the test of choice in patients suspected of having TOS. This test shows the abnormal bony tubercle on the first rib with extrinsic compression of the subclavian innominate junction, which is exacerbated with elevation of the arm above the shoulder. Robotic resection of the medial aspect of the first rib along with disarticulation of the costo-sternal joint has the best reported results to date.
Dynamic ultrasonography for assessing the nerve-fasciae relationship in entrapment syndromes
