AANS Neurosurgeon | Volume 26, Number 3, 2017

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Gray Matters: Bringing Polemic Issues With Inchoate Guidelines Into Sharper Focus

Thoracic Outlet Syndrome

This 47-year-old, right-handed, otherwise healthy gentleman with history of pulmonary embolus presented with right upper extremity pain, numbness and weakness of the right hand grip causing him to drop objects. He repairs roof fire sprinkler systems, work that requires routine sustained arm elevation. His symptoms started after an episode when he experienced significant upward traction to both arms while transporting a heavy cart at work. He notes the symptoms have been progressively worsening in spite of physical therapy and non-steroidal anti-inflammatory medications for a prolonged period of time. He reports pain and numbness in the right mid-supraclavicular region radiating down to the fourth and fifth fingers of the right hand during arm extension, abduction and external rotation over and behind his head. He also reported experiencing right hand swelling and color change to reddish/purple becoming cold to touch.

On physical examination, he has exquisite tenderness over the right supraclavicular region (Erb´s point) with reproduction of symptoms, decreased right radial pulse when elevating arm or shoulder abduction to 180 degrees (Wright’s hyperabduction test) and when rapid hand opening/closing with shoulder abducted to 90 degrees and elbow flexed to 90 degrees (Elevated Arm Stress Test (EAST)). Neck extension and head rotation toward the symptomatic side with inspiration and extension of the arm also reproduced his symptoms (Adson test). His motor examination was normal with no intrinsic muscle atrophy or wasting. There were no objective signs of radiculopathy or myelopathy and the rest of his neurological examination was normal.

An EMG/NCV showed right lower trunk (C8-T1) plexopathy. Duplex studies of the subclavian vessels revealed bilateral arterial waveform dampening with provocative testing. An MRI of the cervical spine was unremarkable for any significant pathology.

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Discussion
Thoracic outlet syndrome (TOS) refers to a constellation of signs and symptoms that arise from compression of the brachial plexus, subclavian artery and subclavian vein by various structures within the confined space of the thoracic outlet. Compression may occur at three sites: the interscalene triangle (delimited by the anterior scalene muscle anteriorly, middle scalene muscle posteriorly and the medial surface of the first rib inferiorly), the costoclavicular space (delimited anteriorly by the middle third of the clavicle, posteromedially by the first rib and posterolaterally by the upper border of the scapula) and the subpectoral tunnel (circumscribed by the pectoralis minor muscle anteriorly and the chest wall posteriorly). Compression may be caused by a prominent or extended C7 transverse process, an anomalous cervical rib, tight fascial or ligamentous bands or first rib abnormalities, anterior scalene muscle hypertrophy or be the result of injury. Historically, this has led to a plethora of terms describing this clinical condition including cervical rib syndrome, scalene anticus syndrome, costoclavicular syndrome and hyperabduction syndrome.

There is also no universal agreement on the diagnosis and management of TOS. Clearly, neurogenic (affecting the brachial plexus) and vascular (affecting the subclavian artery, vein or both) forms are evident and at times both components may co-exist. There are also instances in which patient symptoms are not corroborated by objective testing on physical examination or diagnostic studies (“disputed” TOS). In our practice, we rely on a careful history and physical examination, appropriate diagnostic testing (chest x-ray to rule out cervical rib, EMG/NCV, duplex of subclavian artery and vein, MRI brachial plexus, CTA chest with arm hyperabduction) and repeated evaluations with a multidisciplinary approach. Recent guideline from the Society for Vascular Surgery (SVS) do not even recommend testing other than a chest x-ray and instead rely on the patient’s symptoms and physical examination to a greater extent. However, it is essential to exclude other conditions that can mimic TOS: appropriate clinical and diagnostic testing for cervical disk disease, spinal or foraminal stenosis, cervical spinal cord tumors, cervical syringomyelia, brachial plexitis, ulnar and/or median nerve entrapment neuropathy, nerve sheath tumors, shoulder abnormalities, complex regional pain syndrome, fibromyalgia, apical lung lesions such as a Pancoast tumor, multiple sclerosis (MS) and amyotrophic lateral sclerosis, should be considered and performed.

Tenderness in the supraclavicular space at Erb’s point is very suggestive of neurogenic TOS. The hyperabduction (Wright’s) test is considered positive when a decreased right radial pulse is detected with elevation of the arm and shoulder abduction to 180 degrees; EAST (Roos’) test is considered positive if it reproduces the patient’s symptoms if the patient pumps his or her fists with the shoulder abducted to 90 degrees and elbow flexed to 90 degrees; Adson’s test is considered positive if the patient’s symptoms are reproduced or aggravated with arm and neck extension and head rotation toward the symptomatic side with inspiration. Other clinical findings include vasomotor disturbances with changes in skin color and temperature and the eponymous Gilliatt-Summer hand characterized by atrophy of the abductor pollicis brevis, interosseous and hypothenar muscles.

Conservative management is the initial treatment and quite effective in most cases. It usually involves a combination of carefully directed physical therapy and medical management. The goal of physical therapy for TOS is to reduce abnormal pressure on the neurovascular structures of the thoracic outlet. Patient posture, neck, shoulder and scapular dyskinesia, deep neck flexor weakness, scalene hypertonicity, thoracic spine/rib cage joint restrictions and peri-scapular strength are assessed. Postural education with use of manual therapy and exercises consisting of soft tissue mobilization focused on the scalenes and pectorals. Joint mobilizations and direct pressure on a vertebra or rib aimed at stretching the capsular or periarticular structures along with stretching exercises are performed. Strengthening exercises focused on the serratus anterior, middle/lower trapezius and rhomboids improves resting posture of the shoulder girdle and scapular control with elevation. A course of physical therapy can vary from 12 weeks to six months; improved posture can be expected at six weeks and strength/dynamic control can be expected at 12 weeks.

Medical management is performed in conjunction with physical therapy. Non-steroidal anti-inflammatory medications, anti-neuropathic medications, such as gabapentin and pregabalin, muscle relaxants and short-term opioid medications are titrated to effective symptom management. Scalene triangle corticosteroid injections are occasionally used with both therapeutic and diagnostic utility. Direct injection of both the anterior and middle scalene muscles under ultrasound guidance has also been described, having some element of diagnostic utility prior to decompression.

Surgery is generally reserved for persistently symptomatic patients who are refractory to conservative management. It consists of decompression of the thoracic outlet through a variety of approaches; anterior supraclavicular, transaxillary, posterior subscapular or infraclavicular. The anterior supraclavicular approach, which we prefer, is most common and

Figure 1

allows wide exposure of the supraclavicular plexus and middle two-thirds of the first rib, where most of the potential congenital bands are located. A transverse supraclavicular incision two finger-breadths above the clavicle in the posterior triangle of the neck is made and the platysma divided. The clavicular head of the sternocleidomastoid is mobilized or cut. We mobilize the supraclavicular fat pad laterally preserving the supraclavicular nerves and section the inferior belly of the omohyoid. The thoracic duct and phrenic nerve which lie on top of the anterior scalene muscle are vulnerable to injury. The phrenic nerve can be stimulated to confirm diaphragmatic contraction and protected (Figure 1). The brachial plexus and subclavian artery and vein are also similarly protected.

There are two options in dealing with the anterior scalene muscle: a sharp division down the middle of the muscle with coagulation of the cut ends allows the muscle to shrink away and decompresses the underlying plexus of nerves (Figure 2). Alternatively, sharply removing the anterior scalene muscle via division inferiorly at the rib and superiorly using judicious bipolar cautery to control any bleeding is an option exercised by many vascular surgeons; studies

Figure 2

suggest this may be more effective than simply dividing the muscle. The option of sectioning the middle scalene is also selectively used. There is a risk of injuring nerves that traverse through the muscle itself such as the long thoracic and dorsal scapular nerves. If planning a middle scalene muscle division, it is essential to identify these nerves carefully before proceeding. The transaxillary approach also allows relatively easy access to the ipsilateral first rib but provides limited exposure of the brachial plexus. The posterior subscapular approach is usually for patients who have undergone a previous anterior approach or radiation therapy with scarring; it is rarely employed. It involves extensive muscle dissection, and some nerves such as the long thoracic, dorsal scapular and spinal accessory nerve are vulnerable to injury by this exposure. Pectoralis minor tenotomy (to decompress the subcoracoid segment of the brachial plexus) may be useful in treating recurrent neurogenic TOS.

Success after thoracic outlet decompression is variable, but recent reports suggest an excellent response; however, recurrence of symptoms can occur. Carefully individualizing each case and relying on a multidisciplinary evaluation and approach may be most prudent.

 

THE EXPERTS WEIGH IN

Eric L. Zager, MD, philadelphia

zager-headshot-resizedIn this report, Drs. Jusué-Torres and colleagues present a typical work-related injury with intractable symptoms involving the upper extremity. Unlike the much more common diagnosis of cervical spondylosis, this patient presented with minimal neck pain and marked exacerbation of upper extremity pain, numbness and a sensation of weakness with arm elevation. That is an important differential diagnostic point: The patient with cervical radiculopathy tends to prefer to keep the arm elevated overhead, while the patient suffering with painful neurogenic TOS cannot tolerate arm elevation or repeated arm usage.

As in many neurological disorders, a careful history in patients with suspected TOS is crucial in making a difficult diagnosis; this is particularly true in this controversial disorder, as the exam findings, imaging and electrical studies are often not very helpful or specific. We also use various provocative maneuvers routinely on exam, and find tenderness of the supraclavicular fossa, a positive Tinel’s sign with percussion over the supraclavicular plexus and a positive Roos’ test to be most helpful.  

TOS is really not one clean syndrome. The classic distinction of vascular TOS vs. neurogenic TOS is not always crystal clear. Many patients have an overlap of vascular and neurogenic symptoms, and that should not be surprising: The neurovascular bundle runs through a tight anatomic space, and there are many moving parts in very close association.

The vast majority of symptoms arise from the interscalene triangle where a variety of soft tissue anomalies (fibrous bands, hypertrophic muscles, Sibson’s fascia or suprapleural membrane) and occasionally bony anomalies conspire to compress and irritate the neural elements. We are talking about dynamic compression of the trunks of the plexus in this location (most often the lower trunk takes the brunt of the insult), while the more distal plexus can occasionally be constricted in the costoclavicular space or the subpectoral tunnel. The neurologists only rarely establish a diagnosis of true classic neurogenic TOS with the Gilliatt-Sumner hand and the characteristic pattern of findings on electrodiagnostic studies. The vast majority of patients present with a chronic pain syndrome, often post-traumatic, with very few hard neurological findings and typically unimpressive electrodiagnostic studies. 

We always want to rule out other pathology with MRI of the cervical spine and plexus, and we are now routinely using high-resolution diagnostic ultrasound with provocative maneuvers to help visualize the plexus elements in positions that elicit the worst symptoms. We are also offering ultrasound-guided injections of the scalene muscles for both diagnostic and therapeutic purposes; however, we do not yet know in detail how helpful these are in directing our future care. 

Operative intervention is offered only after a prolonged course of conservative management, unless we are dealing with the rare patient with the true neurogenic TOS, which is often not painful and presents with notable atrophy of the hand intrinsics. For operative intervention, I also prefer the anterior supraclavicular approach, as the anatomy is familiar and the plexus can be thoroughly explored and decompressed. Initially, I divided the anterior scalene muscle and found generally good results, but I then noted an occasional recurrence of symptoms.

In the few cases I have re-explored, I found that the remnant of the scalene muscle was tightly adherent to the plexus, so now I routinely resect as much of the anterior scalene muscle as I can safely. This requires extreme caution to avoid traction or cautery injury to the overlying phrenic nerve. We don’t stop there: We then explore circumferentially around each plexus element as well as the subclavian artery and often divide fibrous bands within the medial aspect of the middle scalene muscle. Occasionally there is a prominent suprapleural membrane (aka Sibson’s fascia) which is found at the depths of the wound medially, near the neural foramina. Most often, we are not resecting the first ribs unless they are malformed. Even cervical ribs and elongated C7 transverse processes are often not the constricting culprits – more often it is the associated fibrous band arising from the tip of the bony element that skewers the lower or middle trunk.

Even though the history of TOS surgery has been checkered with marginal indications, poor results and excessive litigation (particularly when thoracic surgeons were doing these procedures routinely), the current approach with careful patient selection, delicate decompressive surgery and then resumption of physical therapy can have very gratifying results. We are currently reviewing our experience with pediatric TOS and have found the results to be even better than in adults.  

References
1. Toussaint, C. P., & Zager, E. L. (2011). Thoracic Outlet Syndrome, in Youmans JR, Winn HR (eds): Youmans neurological surgery. Philadelphia, PA: Saunders/Elsevier, 2011, Vol 3, pp 2440-2446.

2. Watson, L. A., Pizzari, T., & Balster, S. (2010). Thoracic outlet syndrome part 2: conservative management of thoracic outlet. Manual therapy, 15(4), 305-314. 

3. Peek, J., Vos, C. G., Unlu, C., van de Pavoordt, H. D., van den Akker, P. J., & de Vries, J. P. (2016). Outcome of Surgical Treatment for Thoracic Outlet Syndrome: Systematic Review and Meta-Analysis. Annals of Vascular Surgery. 

4. Sheth, R. N., & Campbell, J. N. (2005). Surgical treatment of thoracic outlet syndrome: a randomized trial comparing two operations. Journal of Neurosurgery: Spine, 3(5), 355-363.

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8th World Congress of Neuroendoscopy
Nov. 1-4, 2017; Cape Town, South Africa

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Nov. 4, 2017 - Nov. 5, 2017; Boston, Mass.

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