Upper plexus thoracic outlet syndrome--case report

Ultrasonographic Diagnosis of Thoracic Outlet Syndrome Secondary to Brachial Plexus Piercing Variation

Structural variations of the thoracic outlet create a unique risk for neurogenic thoracic outlet syndrome (nTOS) that is difficult to diagnose clinically. Common anatomical variations in brachial plexus (BP) branching were recently discovered in which portions of the proximal plexus pierce the anterior scalene. This results in possible impingement of BP nerves within the muscle belly and, therefore, predisposition for nTOS. We hypothesized that some cases of disputed nTOS result from these BP branching variants. We tested the association between BP piercing and nTOS symptoms, and evaluated the capability of ultrasonographic identification of patients with clinically relevant variations. Eighty-two cadaveric necks were first dissected to assess BP variation frequency. In 62.1%, C5, superior trunk, or superior + middle trunks pierced the anterior scalene. Subsequently, 22 student subjects underwent screening with detailed questionnaires, provocative tests, and BP ultrasonography. Twenty-one percent demonstrated atypical BP branching anatomy on ultrasound; of these, 50% reported symptoms consistent with nTOS, significantly higher than subjects with classic BP anatomy (14%). This group, categorized as a typical TOS, would be missed by provocative testing alone. The addition of ultrasonography to nTOS diagnosis, especially for patients with BP branching variation, would allow clinicians to visualize and identify atypical patient anatomy.

Anatomical variations in the brachial plexus roots: implications for diagnosis of neurogenic thoracic outlet syndrome

Neurogenic thoracic outlet syndrome (NTOS) is the most common type of TOS. Typically it results from impingement of the neurovasculature as it passes between the anterior and middle scalene muscles; this classic anatomical relationship being the foundation of clinical diagnosis. Positional testing relies on vascular compromise occurring when the subclavian artery is compressed in this space. This study describes several anatomical variations observed in this relationship. Sixty-five cadavers (35m/30f) were assessed to determine the frequency and extent of brachial plexus branching variants. A total of thirty-one variations from "classic" anatomy were observed (47.7%). In two specimens (3.1%), the entire superior trunk coursed completely anterior to the anterior scalene in a position of relative vulnerability. In 27 instances, a portion of or the entire superior trunk pierced the anterior scalene muscle, and in two, the middle trunk also pierced the muscle belly. Interestingly, while two bilateral branching variations were observed, the majority occurred unilaterally, and almost exclusively on the left side. There were no sex differences in frequency. The high frequency of these variations and their potential to predispose patients to neurogenic TOS suggest that current diagnostic methods may be insufficient in clinical diagnosis. Due to lack of vascular compromise, patients with the piercing variant would not display positive signs on the traditional positional tests. The use of ultrasound to determine the route of the brachial plexus could determine whether this variation is present in patients who suffer from TOS symptoms but lack a diagnosis based on traditional positional testing.

Thoracic outlet syndrome: a neurological and vascular disorder

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.

Anomalous vasculature as direct cause of upper brachial plexus thoracic outlet syndrome

Direct vascular etiologies of upper plexus thoracic outlet syndrome (TOS) other than the subclavian vessels are exceptional. This is a unique case of an anomalous artery and its accompanying vein causing direct compression to the upper brachial plexus causing TOS. All symptoms resolved after successful treatment consisting of ligation and resection of the vessels. This case demonstrates that although direct vascular etiologies causing upper plexus TOS are extremely uncommon, they should be considered in the differential diagnosis.

Rapid recovery of serratus anterior muscle function after microneurolysis of long thoracic nerve injury

Background

Injury to the long thoracic nerve is a common cause of winging scapula. When the serratus anterior muscle is unable to function, patients often lose the ability to raise their arm overhead on the affected side.

Methods

Serratus anterior function was restored through decompression, neurolysis, and tetanic electrical stimulation of the long thoracic nerve. This included partial release of constricting middle scalene fibers and microneurolysis of epineurium and perineurium of the long thoracic nerve under magnification. Abduction angle was measured on the day before and the day following surgery.

Results

In this retrospective study of 13 neurolysis procedures of the long thoracic nerve, abduction is improved by 10% or greater within one day of surgery. The average improvement was 59° (p < 0.00005). Patients had been suffering from winging scapula for 2 months to 12 years. The improvement in abduction is maintained at last follow-up, and winging is also reduced.

Conclusion

In a notable number of cases, decompression and neurolysis of the long thoracic nerve leads to rapid improvements in winging scapula and the associated limitations on shoulder movement. The duration of the injury and the speed of improvement lead us to conclude that axonal channel defects can potentially exist that do not lead to Wallerian degeneration and yet cause a clear decrease in function.