The subclavius posticus muscle: a factor in arterial, venous or brachial plexus compression?

Congenital, Acquired, and Trauma-Related Risk Factors for Thoracic Outlet Syndrome-Review of the Literature

Thoracic outlet syndrome is a group of disorders that affect the upper extremity and neck, resulting in compression of the neurovascular bundle that exits the thoracic outlet. Depending on the type of compressed structure, the arterial, venous, and neurogenic forms of TOS are distinguished. In some populations, e.g., in certain groups of athletes, some sources report incidence rates as high as about 80 cases per 1000 people, while in the general population, it is equal to 2-4 per 1000. Although the pathogenesis of this condition appears relatively simple, there are a very large number of overlapping risk factors that drive such a high incidence in certain risk groups. Undoubtedly, a thorough knowledge of them and their etiology is essential to estimate the risk of TOS or make a quick and accurate diagnosis.

Prevalence and anatomy of the anomalous subclavius posticus muscle and its clinical implications with emphasis in neurogenic thoracic outlet syndrome: Scoping review and meta-analysis

BACKGROUND

The subclavius muscle runs underneath the clavicle. However, there have been a few reports of a duplicated subclavius muscle which is commonly referred to as subclavius posticus muscle due to its orientation being posterior to the proper subclavius muscle. Its occurrence seems to potentially create a narrowing interval at the superior thoracic aperture as it crosses over the brachial plexus. It might also have functional influence on the shoulder girdle.

PURPOSE

To provide comprehensive gross anatomy description of the variant "subclavius posticus muscle" and to investigate its reported clinical implications with emphasis on its involvement in causing brachial plexus compression.

BASIC PROCEDURES

A scoping review with meta-analysis of the gross anatomy of the subclavius posticus muscle was conducted along with investigating its correlation to the thoracic outlet syndrome. Forty-seven articles were pooled through two rounds of the selection process. The relevant information was extracted and meta-analyzed.

MAIN FINDINGS

The scoping review and meta-analysis of the 47 articles revealed a total prevalence of 11/2069 (4.9%); 10/1369 (5.1%) in cadaveric studies, and 1/700 (5.0%) in MRI studies. The subclavius posticus muscle is a short triangular muscle with an average length of 12 cm and an average width of 1 cm. It originates from the sternal end of the first rib in most cases with reported variants of one case originating from the costoclavicular ligament and one case where it was fused with the proper subclavius muscle. Its insertion is more variable: on the superior border of the scapula with variable length in 71.35%, on the coracoid process of the scapula in 25.42%, and on the clavicle in 0.90%. The subclavian nerve seems to be the dominant nerve supply with a 57.6% prevalence, while 25.8% are innervated by the suprascapular nerve. Other reported nerves were the nerve to the myolohyoid (4.5%), accessory phrenic nerve (4.5%), and a direct branch from the brachial plexus (2.0%). The blood supply was reported (only once) to be from the suprascapular artery. However, the venous drainage was not established at all.

PRINCIPAL CONCLUSIONS

The subclavius posticus muscle is a variant muscle occurring with a reported overall prevalence of 4.9%. It can compress the brachial plexus as it runs across at the space of the superior thoracic aperture with exquisite contact, and this can lead to a neurogenic thoracic outlet syndrome. It also can be involved in the vascular thoracic outlet syndrome. Lastly, it is important not to omit its potential influence in shoulder joint instability to some extent.

Modern Treatment of Neurogenic Thoracic Outlet Syndrome: Pathoanatomy, Diagnosis, and Arthroscopic Surgical Technique

Compressive pathology in the supraclavicular and infraclavicular fossae is broadly termed "thoracic outlet syndrome," with the large majority being neurogenic in nature. These are challenging conditions for patients and physicians and require robust knowledge of thoracic outlet anatomy and scapulothoracic kinematics to elucidate neurogenic versus vascular disorders. The combination of repetitive overhead activity and scapular dyskinesia leads to contracture of the scalene muscles, subclavius, and pectoralis minor, creating a chronically distalized and protracted scapular posture. This decreases the volume of the scalene triangle, costoclavicular space, and retropectoralis minor space, with resultant compression of the brachial plexus causing neurogenic thoracic outlet syndrome. This pathologic cascade leading to neurogenic thoracic outlet syndrome is termed pectoralis minor syndrome when primary symptoms localize to the infraclavicular area. Making the correct diagnosis is challenging and requires the combination of complete history, physical examination, advanced imaging, and ultrasound-guided injections. Most patients improve with nonsurgical treatment incorporating pectoralis minor stretching and periscapular and postural retraining. Surgical decompression of the thoracic outlet is reserved for compliant patients who fail nonsurgical management and respond favorably to targeted injections. In addition to prior exclusively open procedures with supraclavicular, infraclavicular, and/or transaxillary approaches, new minimally invasive and targeted endoscopic techniques have been developed over the past decade. They involve the endoscopic release of the pectoralis minor tendon, with additional suprascapular nerve release, brachial plexus neurolysis, and subclavius and interscalene release depending on the preoperative work-up.

Pectoralis minor syndrome - review of pathoanatomy, diagnosis, and management of the primary cause of neurogenic thoracic outlet syndrome

Thoracic outlet syndrome is an umbrella term for compressive pathologies in the supraclavicular and infraclavicular fossae, with the vast majority being neurogenic in nature. These compressive neuropathies, such as pectoralis minor syndrome, can be challenging problems for both patients and physicians. Robust understanding of thoracic outlet anatomy and scapulothoracic biomechanics are necessary to distinguish neurogenic vs. vascular disorders and properly diagnose affected patients. Repetitive overhead activity, particularly when combined with scapular dyskinesia, leads to pectoralis minor shortening, decreased volume of the retropectoralis minor space, and subsequent brachial plexus compression causing neurogenic thoracic outlet syndrome. Combining a thorough history, physical examination, and diagnostic modalities including ultrasound-guided injections are necessary to arrive at the correct diagnosis. Rigorous attention must be paid to rule out alternate etiologies such as peripheral neuropathies, vascular disorders, cervical radiculopathy, and space-occupying lesions. Initial nonoperative treatment with pectoralis minor stretching, as well as periscapular and postural retraining, is successful in the majority of patients. For patients that fail nonoperative management, surgical release of the pectoralis minor may be performed through a variety of approaches. Both open and arthroscopic pectoralis minor release may be performed safely with effective resolution of neurogenic symptoms. When further indicated by the preoperative workup, this can be combined with suprascapular nerve release and brachial plexus neurolysis for complete infraclavicular thoracic outlet decompression.

Bilateral absence of subclavius muscles with thickened costocoracoid ligaments: a case report with the clinical-anatomical correlation

Anatomical variation is defined as normal flexibility in the topography and morphology of body structures. Such variations are not uncommon in muscles, particularly in the upper limb. Subclavius muscle (SM) has a proximal attachment to the first costochondral junction and the muscle fibers are then directed upwards and laterally to get attached distally to the subclavian groove of the clavicle. Having similar attachments as the subclavius, the costocoracoid ligament (CCL) is the thickening of the proximal part of clavipectoral fascia extending up to the coracoid process. Both SM and CCL help in the maintenance of smooth movements of the pectoral girdle and both may not always be present. Absent SM may be due to anomalous development from the muscle matrix that also forms the inferior belly of the omohyoid apart from the SMs. This anatomical variation may be associated with thickened CCLs and can be correlated to the smooth functioning of the pectoral girdle.

Paralysis of the Upper Extremity Due to Acute Thoracic Outlet Syndrome Caused by the Subclavius Posticus Muscle: A Case Report With Literature Review

The subclavius posticus muscle is a rare aberrant muscle that traverses from the costal cartilage of the first rib posterolaterally to the superior border of the scapula. We report a patient having persistent paralysis of shoulder abduction with wrist and finger extension after a humeral neck fracture. Electromyography (EMG) examination revealed injuries to several upper extremity peripheral nerves, including the radial, axillary, and musculocutaneous nerves. Magnetic resonance imaging (MRI) performed at 10 months post-injury showed severe entrapment of the left brachial plexus by the subclavius posticus muscle at the thoracic outlet. The diagnosis of brachial plexus injury due to a rare abnormal subclavius posticus muscle was typically delayed until the MRI was performed for unexplained multiple peripheral nerve palsy. Resection of the aberrant muscle and brachial plexus decompression did not yield significant improvement in the patient’s radial nerve palsy until 6 months after surgery. Entrapment of the brachial plexus caused by the subclavius posticus muscle can cause symptoms of acute thoracic outlet syndrome following trauma to the upper extremity. In a case of inexplicable multiple peripheral nerve injuries in the upper extremity that are not proportional to the degree of trauma, MRI imaging along with EMG is required.

Interclavicularis anticus digastricus muscle in a female body donor: a case report

Background and objectives

Muscular variations of the ventral thoracic wall are generally common and of great clinical interest.

Materials and methods

An unusual muscular variation of the ventral thoracic wall was observed and dissected in a West-European female body donor.

Results

An interclavicularis anticus digastricus muscle was observed and studied. It originated from the manubrium sterni and inserted bilaterally to the clavicles. Both muscle bellies were interconnected by a tendon on the ventral surface of the manubrium sterni. The muscle was innervated by branches of the lateral pectoral nerve.

Conclusions

The interclavicularis anticus digastricus muscle is a muscular variation of the ventral thoracic wall of unknown prevalence. This variation might be of clinical interest in orthopaedics and thoracic surgery. It is also a vulnerable structure during infraclavicular insertion of a subclavian vein catheter or fractures of the clavicle.

Completely thoracoscopic 3-port robotic first rib resection for thoracic outlet syndrome

BACKGROUND

In thoracic outlet syndrome (TOS), the constriction between bony and muscular structures leads to compression of the neurovascular bundle to the upper extremity. Traditional surgical techniques using supra-, infraclavicular or transaxillary approaches to remove the first rib do not usually allow good exposure of the entire rib and neurovascular bundle. We have therefore developed a robotic approach to overcome these limitations.

METHODS

Between January 2015 and November 2020, 38 consecutive first rib resections for neurogenic, venous or arterial TOS were performed in 34 patients at our institutions. For our completely portal approach, we used two 8mm working ports and one 12mm camera port.

RESULTS

The surgery time was between 71 to 270 min (median 133 min, SD+/-44.7 min) without any complications. Chest tube was removed on postoperative day 1 in all patients and the hospital stay after surgery ranged from 1 to 7 days (median 2 days, SD+/-2.1 days). No relevant intra- or postoperative complications were observed and complete or subtotal resolution of symptoms was seen in all patients.

CONCLUSIONS

The robotic technique described here for first rib resection has proven to be a safe and effective approach. The unsurpassed exposure of the entire first rib and possibility for a robotic-assisted meticulous surgical dissection has prevented both intra- and postoperative complications. This makes this technique unique as the safest and most minimally invasive approach to date. It helps improving patient outcomes by reducing perioperative morbidity with an easily adoptable procedure.

Robotic-Assisted Thoracoscopic Resection of the First Rib for Vascular Thoracic Outlet Syndrome: The New Gold Standard of Treatment?

In thoracic outlet syndrome (TOS) the narrowing between bony and muscular structures in the region of the thoracic outlet/inlet results in compression of the neurovascular bundle to the upper extremity. Venous compression, resulting in TOS (vTOS) is much more common than a stenosis of the subclavian artery (aTOS) with or without an aneurysm. Traditional open surgical approaches to remove the first rib usually lack good exposure of the entire rib and the neurovascular bundle. Between January 2015 and July 2021, 24 consecutive first rib resections for venous or arterial TOS were performed in 23 patients at our institutions. For our completely portal approach we used two 8mm working ports and one 12/8 mm camera port. Preoperatively, pressurized catheter-based thrombolysis (AngioJet®) was successfully performed in 13 patients with vTOS. Operative time ranged from 71-270 min (median 128.5 min, SD +/- 43.2 min) with no related complications. The chest tube was removed on Day 1 in all patients and the hospital stay after surgery ranged from 1 to 7 days (median 2 days, SD +/- 2.1 days). Stent grafting was performed 5-35 days (mean 14.8 days, SD +/- 11.1) postoperatively in 6 patients. The robotic approach to first rib resection described here allows perfect exposure of the entire rib as well as the neurovascular bundle and is one of the least invasive surgical approaches to date. It helps improve patient outcomes by reducing perioperative morbidity and is a procedure that can be easily adopted by trained robotic thoracic surgeons. In particular, patients with a/vTOS may benefit from careful and meticulous preparation and removal of scar tissue around the vessels.

Rare Case of Dynamic Thoracic Outlet Syndrome Resolved by an Isolated Subclavius Posticus Muscle Resection: A Case Report

CASE

We reported a dynamic neurogenic left thoracic outlet syndrome (TOS) with a permanent abduction of the fifth left finger. Preoperative magnetic resonance imaging (MRI) assessed the presence of subclavius posticus muscle (SPM). Because of a nonoperative treatment failure, we performed a brachial plexus neurolysis and SPM resection. Immediate postoperative assessment showed an immediate disappearance of the Wartenberg sign.

CONCLUSION

SPM constitutes an underestimated cause of TOS. A careful MRI reading is necessary to make correct diagnosis. Nonoperative treatment includes physiotherapy and can be proposed in first instance. When nonoperative treatment fails, brachial plexus exploration with release of the SPM may result in resolution of symptoms.

The prevalence and characteristics of the subclavius posticus muscle in the adult population on MRI

PURPOSE

The subclavius posticus muscle (SPM) is an aberrant muscle, and the presence of the SPM has a clinical significance, since the SPM might lead to thoracic outlet syndrome (TOS). To date, no radiological study has been evaluated the prevalence of the SPM in the adult population. In this study, we aimed to assess the prevalence of the SPM using magnetic resonance imaging (MRI).

METHODS

We retrospectively reviewed brachial plexus, neck, and thoracic MRI of the patients who underwent MRI for various pathologies. Only the patients whose MRI examinations did not have sufficient image quality and the patients who had any pathology that directly involved the thoracic outlet region were excluded from the study. The observers assessed images in the coronal plane to detect the presence of the SPM. The thickness of the muscle and the distance between the SPM and brachial plexus were also noted.

RESULTS

MRI examinations of 350 patients, 174 males and 176 females, were evaluated. SPM was detected in 29 patients (8.3%). In 6 patients (1.7%), we identified bilateral SPM. The mean thickness of the muscle was 6.10 ± 1.60 mm (range 2.5-10 mm). In 21 sides (60%), the brachial plexus and SPM were touching each other. In the remaining 14 sides (40%), the mean distances between the SPM and brachial plexus were 2.32 ± 0.62 mm (range from 1.7 to 3.6 mm).

CONCLUSIONS

We conducted the first radiological study that evaluated the prevalence of the SPM, and we also assessed the thickness of the SPM and the distance between the SPM and brachial plexus. We highlight that our study might be accounted as a first step for future studies to assess the role of the SPM in TOS.

An Aberrant Subclavius Posticus Muscle: A Case Report

OBJECTIVE

An aberrant subclavius posticus muscle was found during routine dissection of the left infraclavicular fossa of a 60-year-old male cadaver.

PRESENTATION

This aberrant muscle arises antero-medially, from the costoclavicular ligament, runs postero-laterally, over the trunks of the brachial plexus, and postero-lateral has a common insertion with the omohyoid muscle.

CONCLUSION

The presence of such an aberrant muscle may cause a dynamic compression of the subclavian artery and brachial plexus.

Absence of the subclavius muscle with contralateral subclavius posticus muscle: first imaging report

We present a case of a 56-year-old man with pain in in his right anterior shoulder, arm, and hand. MRI studies demonstrated absence of the subclavius muscle with contralateral subclavius posticus muscle. To our knowledge, imaging of the total absence of subclavius muscle has not been previously described. Understanding and recognition of subclavius posticus muscle are important for its potential role in thoracic outlet syndrome.

Thoracic Outlet Syndrome in the Overhead Athlete: A Report of 2 Cases of Subclavius Posticus Muscle

Subclavius posticus muscle is a supernumerary anatomical variation of the subclavius muscle. The aim of this study was to show the possible contribution of the posticus muscle in the development of unilateral thoracic outlet syndrome (TOS) in overhead athletes, presenting hypertrophy of the dominant arm due to their sport activity. Reported here are 2 young overhead athletes complaining pain, paresthesia, weakness in the dominant upper limb, although presenting none of the main shoulder and neurological disorders. After developing subclavian vein thrombosis, TOS was suspected and finally diagnosed by dynamic magnetic resonance angiography, which also showed bilateral subclavius posticus muscle in both patients. Despite bilateral subclavius posticus, TOS was only evident in the dominant limb in which the association of hypertrophy of lateral cervical muscles, resulting from the overhead sport activity, to the subclavius posticus likely led to a significant reduction of the upper thoracic outlet space.

Differential diagnosis of a rare case of upper limb pain: Paget-Schroetter syndrome in a doner kebab chef

[Purpose] Paget-Schroetter syndrome (PSS) is an uncommon deep vein thrombosis of the axillary and subclavian veins which may occur spontaneously, but is usually caused by excessive upper limb activity. PSS is clinically similar to other upper limb musculoskeletal disorders and soft tissue infections, and this may lead to delay in correct diagnosis in its early stages. The aim of our case report is to discuss this rare condition with reference to the available literature. [Subjects and Methods] Here we report the case of a doner kebab chef who complained of swelling and pain in his right arm around the biceps muscle. The initial diagnosis was biceps tendon rupture, for which the patient underwent magnetic resonance imaging (MRI) of the right arm and shoulder. Since the MRI revealed no pathological findings, right upper limb venous Doppler ultrasound analysis was performed. Subacute thrombosis materials were detected in the subclavian, axillary, and brachial veins. [Results] With rapid anticoagulant therapy, the patient’s symptoms quickly improved. [Conclusion] Early diagnosis and treatment of PSS is critical for preventing potentially fatal complications such as pulmonary embolism. Prophylaxis is important for preventing recurrent thrombosis and for avoiding the development of post-thrombotic syndrome. PSS should be considered a possible cause of painful swelling of the upper limbs, especially in young, active patients who use their arms excessively.

Neurogenic thoracic outlet syndrome due to subclavius posticus muscle with dynamic brachial plexus compression: a case report

Background

Neurogenic thoracic outlet syndrome is an underestimated cause of brachial weakness and pain. The subclavius posticus muscle (SPM) is an aberrant muscle originating from the medial aspect of the first rib reaching to superior border of the scapula, which may cause, depending on its activation, dynamic compression of the brachial plexus.

Case presentation

In the present study, we report about a 32-year-old male caucasian patient with weakness in radial deviation of his left hand. An isolated macrodactyly of his left middle finger had been operated twice. Electroneurography showed a carpal-tunnel-syndrome (CTS) on the left side. MRI of the brachial plexus revealed an additional muscle in the costoclavicular space, identified as SPM. To our knowledge, this is the second case report of a neurogenic thoracic outlet syndrome due to SPM, and the first case described with isolated macrodactyly and CTS in the same patient.

Conclusion

If complaints about hand weakness are only reported in cases of distinct hand positions, a dynamic compression of the brachial plexus by SPM may be the cause. A neurogenic thoracic outlet syndrome may facilitate the development of CTS.

Subclavius posticus: an anomalous muscle in association with suprascapular nerve compression in an athlete

Subclavius posticus is a rare anomalous muscle that traverses from the costal cartilage of the first rib posterolaterally to the superior border of the scapula. We present an athlete who presented with incapacitating suprascapular nerve compression associated with a subclavius posticus diagnosed by MRI. Symptoms were relieved, and function was restored by decompression of the nerve and excision of the anomalous muscle. We present this case to bring awareness of the subclavius posticus as an anatomic variant and a potential additional source for compression in suprascapular neuropathy. We recommend high-resolution magnetic resonance imaging to evaluate cases of isolated suprascapular neuropathy.

LEVEL OF EVIDENCE

V.

The subclavius posticus muscle: an unusual cause of thoracic outlet syndrome

We present the case of a 30-year-old female, complaining of thoracic outlet compression symptoms caused by a supernumerary muscle, the subclavius posticus, accompanied by a caudally inserted middle scalenus muscle on the second rib. This rare anatomic variant was clearly shown on CT angiography and MRI images and surgical treatment was successful. As first described by Rosenmuller in 1800, subclavius posticus is a supernumerary muscle originating from the cranial surface of the sternal end of the first rib, running laterodorsally beneath the clavicle, and inserting into the superior border of the scapula. Its role in thoracic outlet syndrome has been seldom demonstrated in living patients nor described in imaging, although it is theoretically easily recognizable on modern imaging modalities. It should be taken into account during workout of patients with thoracic outlet syndrome, since it can be potentially treated.

High-definition video-assisted transaxillary first rib resection for thoracic outlet syndrome

Transaxillary first rib resection is a well-established effective surgical treatment for patients with symptomatic thoracic outlet syndrome, but surgical access may be limited and visualization is constrained. The use of high-definition video-assisted imaging overcomes these limitations. The use of high-definition video-assisted visualization of the anatomy enhances the surgeon's tactile feedback of the rib from the small open wound and is effective in providing better surgical access and allows clear identification of vital structures for the operating surgical team. This technique enhances the appreciation of anatomic detail, situational awareness of the team, and allows for more efficient assistance to the surgeon. Improved visualization also facilitates effective education of nurses, residents, and students.

MRI findings in thoracic outlet syndrome

We discuss MRI findings in patients with thoracic outlet syndrome (TOS). A total of 100 neurovascular bundles were evaluated in the interscalene triangle (IS), costoclavicular (CC), and retropectoralis minor (RPM) spaces. To exclude neurogenic abnormality, MRIs of the cervical spine and brachial plexus (BPL) were obtained in neutral. To exclude compression on neurovascular bundles, sagittal T1W images were obtained vertical to the longitudinal axis of BPL from spinal cord to the medial part of the humerus, in abduction and neutral. To exclude vascular TOS, MR angiography (MRA) and venography (MRV) of the subclavian artery (SA) and vein (SV) in abduction were obtained. If there is compression on the vessels, MRA and MRV of the subclavian vessels were repeated in neutral. Seventy-one neurovascular bundles were found to be abnormal: 16 arterial-venous-neurogenic, 20 neurogenic, 1 arterial, 15 venous, 8 arterial-venous, 3 arterial-neurogenic, and 8 venous-neurogenic TOS. Overall, neurogenic TOS was noted in 69%, venous TOS in 66%, and arterial TOS in 39%. The neurovascular bundle was most commonly compressed in the CC, mostly secondary to position, and very rarely compressed in the RPM. The cause of TOS was congenital bone variations in 36%, congenital fibromuscular anomalies in 11%, and position in 53%. In 5%, there was unilateral brachial plexitis in addition to compression of the neurovascular bundle. Severe cervical spondylosis was noted in 14%, contributing to TOS symptoms. For evaluation of patients with TOS, visualization of the brachial plexus and cervical spine and dynamic evaluation of neurovascular bundles in the cervicothoracobrachial region are mandatory.

Axillary arch in human: common morphology and variety. Definition of "clinical" axillary arch and its classification

In this work the authors summarize the extensive information available concerning the best-known variant muscular structure in the region of the human axilla--the axillary arch. Emphasis has been placed on the common morphology and variety of the axillary arches. From the anatomical descriptions, the authors extract the characteristics of a group of "typical" axillary arches and also noted the descriptions of a group of "unusual" axillary arches found in the recent literature. The axillary arch terminology, incidence in human population, innervation and origin are discussed. The clinical significance of the axillary arch is presented briefly and the need of a new concept for the axillary arch is stated. In conclusion, for the purpose of clinical practice, a new term--"clinical" axillary arch is defined, and its proper clinically oriented classification is presented.

Axillary arch in Bulgarian population: clinical significance of the arches

In order to study the incidence of the axillary arch in the Bulgarian population, we examined the axillary regions of 56 formol-carbol fixed human cadavers and observed two cases with a unilateral axillary arch. In the first case, the variant structure was situated on the right side of a 58-year-old female cadaver. The axillary arch extended from the lateral border of the latissimus dorsi to the posterior layer of the pectoralis major tendon. In the second case, the axillary arch was found on the left side of a 63-year-old male cadaver and had the same attachment points as in the first case. The innervation and blood supply of the arches are discussed. We have also reviewed extensive information concerning the clinical importance of the axillary arch, and for the first time, it was summarized clearly for clinicians. The summary consists of three parts: "diagnosis" of the axillary arch by physical investigation or imaging techniques; the axillary arch and surgical interventions in the region of the axilla; the axillary arch as an entrapment site for the axillary vessels and nerves.

An evidence-based review of magnetic resonance angiography for diagnosing arterial thoracic outlet syndrome

Arterial thoracic outlet syndrome (TOS) can be difficult to diagnose clinically. Recently, Magnetic Resonance Angiography (MRA) has been used to assist in the diagnosis of arterial TOS. The purpose of this article is to survey the current literature to establish the evidence for or against the use of MRA in the diagnosis of arterial TOS. The evidence-based search was conducted using PubMed, PEDro, Hooked on Evidence, EBM Journals, Ovid, Cochrane, and E medicine. The studies were graded as to the strength of recommendation and to the actual level of evidence. Statistics were calculated when sufficient data were present. The search yielded a total of seven studies. The studies received grades of recommendation that ranged from B to D. The current evidence in support of MRA as a valid test for diagnosing arterial TOS is weak and studies are not based on strong design.

Axillary arch: Potential cause of neurovascular compression syndrome

During routine bilateral dissection of 64 upper limbs in 32 adult human cadavers, four cases of an axillary arch, a muscular anomaly, were found. In one case, the axillary arch presented on both sides and in two cases it presented unilaterally on the right side. The innervation and relationships of the axillary arches are reported and the surgical significance of the anomaly is discussed.