The syndrome can be divided grossly into vascular TOS and neurogenic TOS (NTOS). The vascular form can target the subclavian artery, causing distal ischemia, or the subclavian vein, characterized by repetitive thrombosis during exercise, which is called Paget–Schroetter syndrome. The neurogenic counterpart, which is the topic of the current chapter, generally affects the inferior primary trunk, though this can vary. In recent years, subcategorization of neurogenic TOS into so-called true neurogenic TOS (TNTOS) and disputed neurogenic TOS (DNTOS) has become more widely accepted. Of these, the former produces motor changes, including simultaneous atrophy of the thenar and hypothenar eminences and sensory loss in the lower trunk distribution (the so-called Gilliatt-Sumner hand). ² In contrast, DNTOS is characterized by sensory changes alone in the upper extremity, including pain that typically spreads through the territory of the lower trunk, but which also can affect the entire upper limb, the neck, and/or the shoulder. By definition, DNTOS is not associated with atrophic changes or sensory loss in the muscles of the hand, lest it be called TNTOS.

The first step toward diagnosing TOS is suspecting it. In our experience, many patients bounce between several different physicians, receiving a broad constellation of ineffective treatments. Once the correct diagnosis is made, treatment will depend on the anatomical elements affected, the cause, and the site of compression.

15.2 Diagnosis and Management of TOS

15.2.1 Important Concepts Regarding TOS

TNTOS is a well-defined entity, a fact that allows for relatively easy diagnosis and treatment. It predominantly affects young people, typically ranging from 15 to 35 years old. Its symptoms are both motor and sensory: the usual presentation is a Gilliatt-Sumner hand: an atrophy of the thenar and hypothenar eminences ( ▶ Fig. 15.1), associated with pain, dysesthesias, paresthesias, or hypo/anesthesia in the lower trunk territory, which includes the little finger and medial side of the ring finger, and the medial forearm and arm, with preserved sensation throughout the rest of the hand, mediated by the noncompressed primary upper trunk of the brachial plexus. This clinical presentation is almost pathognomonic, since very few other entities share this picture. An intramedullary or extramedullar–intradural tumor or degenerative disease affecting anterior horn neurons—in the latter case, without sensory impairment—can share some of the clinical findings described before. Also, an ulnar neuropathy can share some of the findings of TOS, but the involvement of the thenar eminence as well as the sensory loss in the forearm do not occur in an ulnar nerve lesion.

There is a broad constellation of clinical signs and tests described to diagnose both TNTOS and DNTOS such as Adson’s test, Wright’s test, the Roos test, and the Halsted test, among many others. For clinical practice, it is important to note that none of these tests is highly specific or sensitive, with many positive tests present in the normal population. In our experience, two good methods by which to elucidate tension or compression within the thoracic outlet are supraclavicular percussion of the brachial plexus and the interscalene space, and arm abduction associated with contralateral rotation of the head, both of which generate sensory symptoms. This being said, these signs are also neither highly sensitive nor specific.

The typical patient who presents with TNTOS is a thin, tall woman with slouching shoulders, though this is not always the rule. Nevertheless, it is extremely uncommon to see an overweight man of short stature with this clinical picture, as his anatomy does not predispose him to lower trunk compression, even in the presence of a cervical rib.

Of course, neurophysiological studies will show abnormalities in such patients, as denervation of the thenar and hypothenar muscles is easily demonstrated, also involving the flexor carpi ulnaris and flexor digitorum profundus of the fourth and fifth digit. Other neurophysiological abnormalities can be expected in this picture, as reduced or absent sensory responses in the ulnar nerve and in medial cutaneous nerve of the forearm.

Imaging plays a very important role in the management of both TNTOS and DNTOS. TNTOS is always associated with a compression site, such as a cervical rib, the first rib, an anomalous ligament, and a supernumerary muscle. It is important to obtain a high-quality computed tomography (CT) scan with a bone window of the thoracic outlet, together with a high-quality magnetic resonance imaging (MRI). Both studies will help determine the compression site, thereby confirming the diagnosis and assisting in the planning of subsequent surgery ( ▶ Fig. 15.2, ▶ Fig. 15.3, ▶ Fig. 15.4).

It is important to keep in mind that cervical ribs are present in a relatively high percentage of the normal population. ³ As such, the presence of one, on its own, does not confirm TOS. Similarly, the absence of clear pathology on imaging does not rule out the diagnosis of TOS when the clinical and neurophysiological pictures are compatible, since up to one-third of compressive structures are identified during surgery, most of them anomalous ligaments that are difficult to visualize on preoperative MRI.

Once TNTOS is diagnosed, our approach is to offer the patient surgical decompression as first-line management. This is a completely different strategy than the one we adopt for DNTOS. In TNTOS, the patient already has distal motor and sensory compromise caused by nerve compression in the proximal limb. Any time delay decompressing the brachial plexus can interfere with eventual motor recovery as, even after decompression, the nerve fibers have a long way to go to reach the hand (nearly 1 m, with a growing speed of 1 mm/day).

Our preferred surgical approach is the standard supraclavicular technique. We start with a 6-cm transverse cervical incision, which is a bit shorter than what we generally use to expose the brachial plexus for traumatic injuries. After dissecting the platysma and the cervical aponeurosis, the omohyoid muscle is retracted to provide access to the brachial plexus. It is extremely important to individualize each of the three primary trunks of the brachial plexus under stimulation, as well as the subclavian artery, before starting any resection procedure, to minimize the risk of damaging any of the neurovascular structures—typically the lower trunk, which is being compressed by a cervical rib or some other anomalous structure. Palpation may help to identify the site of compression, especially if it is within the interscalene space. In addition, intraoperative mobilization of the upper limb may be useful for detecting infraclavicular narrowing within the brachial plexus’ path toward the arm. If compression is caused by a ligament, simple sectioning should be enough to correct the problem. However, if a cervical or first rib needs to be resected, Kerrison rongeurs should be used, cautiously, to resect the bone structures, taking care not to damage the plexus and surrounding vessels. Removing the periosteum before rib resection has some advantages, including reduced bleeding and creating a definitive surgical plane in which no neurovascular structures will be found ( ▶ Fig. 15.5).

Related posts:

Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts or Tubes Nerve Injuries: Anatomy, Pathophysiology, and Classification Malignant Peripheral Nerve Sheath Tumors Ultrasound in Peripheral Nerve Surgery Nerve Anatomy of the Upper Limbs

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