The literature about anatomy, damaging factors, and treatment is so immense and differing in detail that we have to restrict our statements to personal experiences. Citations of literature will also be limited to examples which are representative of specific viewpoints.

We must define the neurogenic form of the syndrome as a nerve irritation syndrome. The five cervical nerve roots run together with the subclavian artery and vein between the scalene muscles laterally and downward. The two lower roots first rise a little through the upper thoracic outlet, and then unite to the inferior trunk which turns downwards. The interior margin of the first rib and sometimes, additionally, a cervical rib has thereby to be overcome. This anatomical situation is in itself completely normal because it is pre-existing in every human. An irritation syndrome of the inferior trunk can, however, start when anomalies or phylogenetically residual structures occur with fibrous ligaments within the scalene muscles, additional scalene muscles, fibrous ligaments between an elongated cervical transverse process and the internal margin of the first rib. Sometimes, if a cervical rib is present, such a fibrous band starts from its end, and runs obliquely through the thoracic outlet to insert somewhere at the first rib. Slim persons with a long and thin neck, predominantly women, are particularly prone to develop lower plexus irritation due to these structures. We should not forget that additional structures run transverse between the scalene muscles and fibrous bands: the subclavian artery and vein, and the transverse colli artery sometimes of large caliber. Pulsating forces within the arteries are quite able to press the comparably soft nerves against the fibrous ligaments. Due to arm abduction, daily activities, or unfavourable positioning overnight, the pre-existing narrowness in the thoracic outlet increases so that vascular and neurogenic symptoms will easily be induced or will deteriorate.

In the thoracic outlet we are not confronted with a particularly narrow tunnel as elsewhere in limbs, but exclusively with an unfavourable combination of life-long pre-existing structures which leave behind a narrowness. The onset of symptoms is, therefore, usually independent of any incident or injury. Typical damaging factors are often unknown. Instead, symptoms start spontaneously. Patients almost never have a reasonable explanation as to why and exactly when discomfort came into their life. Therefore patients and physicians take a long time to realise that a thoracic outlet syndrome might be the answer.

Patients’ complaints consist of electric-current-like sensations almost always irradiating into the ulnar aspect of the hand. Sometimes they observe these disturbing sensations during special arm positions or movements. In cases that have progressed further, patients sustain atrophy of the intrinsic hand muscles. Permanent numbness is not in the foreground, but it is discomfort by disturbing dysesthesias instead. As most of these patients with thoracic outlet syndrome don’t present any objectively noticeable deficits, physicians often suspect that patients are exaggerating their symptoms.

The onset of symptoms is usually unrelated to any trauma; they start spontaneously, and they increase chronically. Nevertheless, very rarely, the patient is able to remember a certain period of time when the symptoms actually emerged. Sometimes he even discusses a potential incident which he then suspects is responsible, like having carried heavy moving boxes on his shoulder in the past.

The typically nonspecific symptoms may be presented bilateral. On the other hand, the existence of a cervical rib on only one side does not really dispose which side is symptomatically affected. As fibrous ligaments are already mentioned as being responsible for symptom origin, the side and size of a cervical rib that has been examined in the patient’s X-ray do not determine which is the affected side of a plexus irritation. We even observed the opposite situations more frequently with a cervical rib on one side and symptoms due to fibrous bands on the other. Nevertheless, bilateral symptoms are possible with and without cervical ribs, with and without the enlargement of the seventh vertebra’s transverse processes, but always in cases of very slim persons.

From the neurological viewpoint it may be important that the Trömmner reflex runs through the inferior trunk, and that the Roos testing (paresthesias during finger motion with arms abducted, elbow joints 90° flexed, and hand palms to outside) turns out pathologically on the affected side. In our own experience, we particularly rely on the findings during supraclavicular palpation: this maneuver presses nerves against the disturbing ligamentous structure and immediately increases the amount of dysesthesias. We are convinced that this sign is a real aid in reaching the diagnosis. It indicates the location of a slightly degenerating and regenerating process like the Tinel sign. It even indicates the affected structure of the brachial plexus, namely, predominantly, the inferior trunk. By doing so, the patient observes dysesthesias exactly in the sensitive distribution area of the affected trunk. This area is similar to a dermatome, and completely differs from an autonomous peripheral nerve distribution area; for instance, numbness or dysesthesias of the ulnar nerve present an exact border in the middle of the fourth digit, whereas inferior trunk irritation also involves the third digit, sometimes with a border in the middle of the third digit. Of course, it should not be a matter of discussion that a cervical disc protrusion C6-7 has to be excluded before any thoracic outlet surgery is indicated.

As mentioned above, thoracic outlet syndrome is a controversial topic in the literature. Besides TOS resulting from vascular compression, a neurogenic form occurs. The neurogenic TOS can be further subdivided into a disputed and a true form. The majority of neurogenic TOS belongs to the disputed form (95 %), whereas the true neurogenic TOS is very rare and accounts for less than 1 % of cases [16]. The true neurogenic TOS is characterised by an affection of the inferior trunk of the brachial plexus together with objective diagnostic findings, whereas the disputed neurogenic form of TOS produces only subjective symptoms like chronic pain. In contrast to carpal tunnel syndrome and ulnar neuropathy at the elbow, unfortunately, there are no standardized guidelines regarding the EDX in the diagnosis of TOS at the moment. One reason is certainly its rarity. In this section we will focus on the EDX in the diagnosis of the neurogenic forms only. Regarding vascular TOS, please refer to the specialist literature. Taking into account the anatomy and pathophysiology, the main goal of EDX is to demonstrate a lesion of the inferior trunk, and, on the other hand, to exclude other pathologies which are similar to TOS, e.g. neuropathy of the ulnar nerve or affection of nerve roots C7 and C8. This easily succeeds in advanced stages of true neurogenic TOS with a pre-existing axonal lesion, but those cases where only a transient compression without permanent damage of neural structures occurs are rather difficult to detect (disputed neurogenic TOS). The registration of f-waves of the ulnar and median nerves in neutral position and after provocative maneuvers is unspecific, and a reduction of amplitudes of motor-evoked potentials after provocation was reported in two cases only [17, 18]. The intramuscular anterior scalene block may serve as a diagnostic tool for disputed neurogenic TOS; it temporarily blocks and paralyzes the muscle and allows the first rib to descend, thereby decompressing the thoracic outlet. Pain relief following this diagnostic intervention may serve as a positive predictor when surgery is considered [19]. Demyelinising nerve damage (true neurogenic TOS) instead increases the chances of obtaining electrically abnormal findings. A pathologically changed sensory nerve conduction study of the medial antebrachial cutaneous nerve (sensory latency over 2.4 ms, latency difference of 0.3 ms or more, amplitude under 10 μV, and amplitude ratios of 2.0 or more) is therefore suggested as the most reliable approach. Considering patients with true neurogenic TOS, 40 out of 41 had at least one of these four diagnostic criteria [20]. Furthermore, it can simultaneously exclude a supraganglionic root lesion and a neuropathy of the ulnar nerve. It has to be valued superior to the simple registration of sensory nerve action potential of the ulnar nerve from the fifth finger, which is pathological in the case of true neurogenic TOS as well as in the case of ulnar neuropathy [20]. Other tests have been described in the literature. Fractionated motor nerve conduction studies both of the ulnar and median nerves together with registration of the corresponding f-waves may be helpful. Reduction in segmental motor nerve conduction velocity to <85 m/s of either the ulnar or median nerves across the thoracic outlet should corroborate the clinical diagnosis [21]. A similar test is the registration of compound muscle action potential latencies of the abductor pollicis brevis and abductor digiti minimi muscles after magnetic stimulation of the brachial plexus. Compound muscle action potential latency of the ABP over 11.04 ms and of the ADM over 10.60 ms can indicate a true neurogenic TOS [22]. Another useful diagnostic tool is the registration of dermatomal and mixed nerve somatosensory evoked potentials (SEPs); however, the abnormality rate for both ulnar and C8 dermatomal SEPs was 100 %-significant only in a small group of advanced disease with severe muscular atrophy, whereas in earlier clinical stages, this rate dropped significantly to 50–67 % [23]. If primary demyelization is followed by secondary axonal loss, or if axonal damage primarily occurred, needle electromyography can easily demonstrate these changes by analysis of the distribution pattern of denervation in several muscles (see Sect. 5.​6.​2). In true neurogenic TOS the abnormalities occur in all muscles supplied by the root C8, and they do not occur in the paravertebral musculature of the cervical spine [24, 25]. This phenomenon helps to differentiate TOS from root C7 and C8 lesions due to cervical disc protrusion. In summary, needle electromyography together with registration of sensory nerve action potential of the medial antebrachial cutaneous nerve plays the key role in the diagnosis of true neurogenic TOS.

High resolution ultrasound and 3 T-MR imaging provide an important diagnostic tool to detect pathological irritations of the brachial plexus and the cervical nerve roots, whereas EDX is nonspecific. High resolution ultrasound is a cost effective alternative to MR imaging outside the spinal cord [26]. Both high resolution ultrasound and MR are able to define the underlying pathology of brachial plexus involvement, e.g. of neoplasia, traumatic, or inflammatory origin, or due to congenital bone variations and fibromuscular anomalies [26, 27]. Using the transverse processes of the cervical vertebra as a landmark, it is easy to identify the cervical nerve roots with high resolution sonography. Taking into account that the transverse process of C7 has only a posterior tubercle, it becomes easier to determine the root level. In most individuals, this landmark will allow to start the examination of the whole course of nerve roots C4–C7 from the foramen to the interscalene space, and, furthermore, of its trunks above of the clavicle. In non-obese individuals, the root C8/TH1 and the brachial plexus below the clavicle are mostly visible [28]. Normal values of CSA (nerve roots C5–C8 and brachial plexus above of the clavicle) have been published only in a few studies to date [29–31]. At present, experience regarding differential diagnosis between true and disputed neurogenic TOS starts using high resolution ultrasound. Figures 8.2 and 8.3 illustrate imaging abilities. According to our experience in 6 cases, fibrous bands and cervical ribs always demonstrated the same appearance wedge/sickle-shaped with hyperechoic edge of the scalene muscles as well as with a hypoechoic and thickened inferior brachial plexus trunk. External compression with the probe led to an indentation of the subclavian artery (Fig. 8.3). MR imaging additionally provides the opportunity to demonstrate the T2 nerve lesion in the case of entrapment (see Chap.​ 6) and the administration of contrast agent. This may be helpful in differentiating between entrapment from other types of pathology such as neoplasm or inflammatory immune neuropathies and to localize the site of entrapment precisely – supraclavicular, infraclavicular, and subclavicular entrapment possibilities have at least to be considered [26, 27].

As already outlined in the introductory remarks of this book, all young patients want relief of pain symptoms. Besides new diagnostic means, we primarily continue to rely on the Tinel sign which can be elicited when the nerves are pressed by the physician’s fingertips against the irritating structure in the supraclavicular triangle.

The literature is full of advice on how to approach the proximal part of the brachial plexus in the case of mechanical irritation. The history of this development can be derived from Atasoy’s extensive presentation [32]. The thoracic outlet syndrome is defined as a focal irritation. Consequently, the approach has to remain as small as possible. Personal experiences over more than two decades regarding the disputed and true neurogenic cases are as follows. First rib resection as often advocated is not mandatory; this also holds true in cases with associated vascular symptoms which can even consist of artery embolism or venous incidents like pulmonary embolism in patient’s history. Inferior trunk damage following rib resection as sporadically observed means an intolerable complication; it has therefore to be avoided in all cases. Partial cervical rib resection was necessary in about 50 %. Complete scalenotomy is unnecessary because muscle fibers do not compress nerves. However, ligamentous fibers hidden between muscles have to be identified and transected completely. In a single case of middle trunk compression, an elongated transverse process of C6 was shortened. When the internal margin of the first rib is particularly sharp, it can be rounded off by means of punches in order to reduce its additional irritating role. The supraclavicular approach was always sufficient to achieve vascular and nerve decompression and thus relief of symptoms. However, there is one restriction to be stated: all cases we operated on in this period always had neurogenic symptoms and, infrequently, additional vascular ones. Pure vascular thoracic outlet syndromes were not included in our series because, in our region, they are included in the field of vascular and thorax surgery.

Theoretically, three different approaches of different extensions to the thoracic outlet region are available, and, of course, for several decades all of them have been considered to be equally successful: the superior approach through the lateral neck triangle [33–35], the transaxillary approach which needs first rib resection [36, 37], and the posterior subscapular approach which is restricted to recurrent cases [34, 38]. Few authors recommend a combination of these options [39]. The whole history of recommendations since 1861 can be followed up – as already mentioned – in the comprehensive contribution by Atasoy in 1996 [32].

The main objections to the transaxillary approach are possible damage of the inferior trunk and a rather hidden localized cervical rib if existent [40], to the supraclavicular approach damage of the phrenic nerve [40]. Probably due to the surgeon’s experience, these complications remain rare. Nevertheless, in reality, they are intolerable. Another intolerable complication is reported by Millesi et al. in 2007: sliding capacities of roots and trunks have to be preserved. The fat tissue which surrounds the nerves allows this sliding during extensive arm motion. This tissue has to be kept aside and never removed [41]. Secondary bleedings leave behind scar tissue and cause severe adhesions. A postoperative suction drainage of 2 or even 3 days is therefore mandatory in our experience. Intra-operative looping of roots and nerves irritates mechanically; it could cause the surgeon to induce damage on previously untouched and normally functioning nerves. We should remember that the myelin sheath of the nerve fiber is rather sensitive; its damage may end up as grade I lesion in accordance with Sunderland’s classification detailed in Sect. 3.​1.

A small skin incision, 2–3 cm parallel to the clavicle, gives enough space. The skin in the neck region is extremely flexible and elastic so the actual approach site can easily be extended by two self-holding retractors. Of course, these retractors should not touch any nerve structure. Particular care has to be taken with the expected course of the phrenic nerve at the opening of the exposure. Adjacent, we find the above-mentioned package of loose fat tissue which we enter by using spreading movements of our scissors. We don’t cut through the tissue both in order to identify small venous vessels which have to be coagulated and individually transected and in order to avoid injury to the important structures lying underneath. By doing so, the omohyoid muscle is isolated within the fat package and can be looped and kept away. Above the muscle, by palpation with the finger tip, it will be helpful to feel and identify where superior and middle trunks run laterally and downward. A little more medial, the anterior scalene muscle can be exposed. By longitudinally spreading movements a careful opening of its surrounding membrane finally leads to the phrenic nerve. Spreading movements of scissor tips must always remain parallel to the expected structure. Instruments that keep nerves such as the phrenic nerve away must always to be placed in such a way that avoids harm or even kinking. During the surgery, all these instruments have to remain under permanent control. We use Langenbeck retractors and never loop nerves. The phrenic nerve acts as border: the whole exposure remains lateral to it because, if medial to it, the surgeon is in danger of damaging the internal jugular vein and the vagus nerve. The superior trunk – previously identified by fingertip – is now carefully isolated far enough, with the middle trunk next to it. At this point, both trunks can be slightly retracted upwards and lateral. Under them, palpation with fingertip will help, first, to find the irritating structure such as a fibrous band, and, second, to identify the subclavian artery which runs parallel to and under the clavicula, but sometimes also abnormally cranial convex curved. Before transecting or even removing any structure which you suppose to be responsible for the symptoms, a reliable identification of the inferior trunk and its division into the two centrally running roots C8 and T1 is mandatory. In most cases, the inferior trunk is flattened, and it rides across the band to lateral. Anatomical variations at root level, e.g. pre- and post-fixation of the brachial plexus, or a missing medial trunk are confusing [42, 43]. Prior to transecting the disturbing fibrous band, and sometimes, additionally, to opening a hypertrophic supra-pleural membrane you must have identified and isolated each structure. Along with this most important step, you can take a punch either to round off the internal margin of the first rib or to remove a cervical rib piece by piece, the latter however as extensively as possible. Rough bone edges left behind can cause new irritations. Before starting rib removal, its periost has to be carried off in order to skeletonise the bone. This procedure avoids injury to the parietal pleura and therefore reduces risks of pneumothorax decisively. Retracting instruments to keep nerves away again have to be under your permanent control. The suction in your left hand can aid as retractor in addition to instruments operated by your assistant.

As previously mentioned, a suction drain for 2 or even 3 days is necessary to exclude secondary bleeding and scarring. Before wound closure, the fat tissue is replaced into the supraclavicular groove. In addition, within this space are many small lymph vessels from which extravasations of lymph liquid will occur; this quickly stops when the wound sticks under suction (Fig. 8.4).

We therefore prefer hospitalization of these patients for no less than 4 days. In only one case a pneumothorax complication and the need for thorax drainage extended hospitalization. We have had no cases of phrenic nerve lesion nor recurrences. In one of our recent patients, a female physiotherapist with a fuller figure, the elicitable pain disappeared at once; however two days later there was a sudden onset of a neuropathic pain in the neck and lateral triangle region. We are aware of criticism but these selected patients are in permanent contact with each other via the internet; thus problems come to light very quickly nowadays.