new perspectives on neurogenic thoracic outlet syndrome

New Perspectives on Neurogenic Thoracic Outlet SyndromePublished on Practical Pain Management (http://www.practicalpainmanagement.com)

New Perspectives on Neurogenic Thoracic OutletSyndrome

The quality of life for patients with neurogenic thoracic outlet syndrome is profoundly diminished.Emerging evidence supports minimally invasive chemodenervation of the cervicothoracic musculaturewith onobotulinum toxin as a treatment option.By Paul J Christo, MD, MBA [1] Volume 14, Issue #8

[2]The definition,incidence, diagnosis, and treatment of thoracic outlet syndrome (TOS) are somewhat controversial.Originally coined in 1956, the term TOS indicated a compression of the neurovascular structures in theinterscalene triangle corresponding to the possible etiology of the symptoms.1 The controversy iscentered on the fact that TOS refers to the anatomy or location of the problem without identifying thecauseeither vascular or neurogenic.

Therefore, TOS generally is defined as a group of disorders caused by compression of the brachialplexus, subclavian artery, or subclavian vein in the thoracic outlet, the area between the clavicle(collarbone) at the base of the neck and the first rib, including the front of the shoulders and chest. TOSis a progressive condition marked by the impingement of the nerves and blood vessels that feed thethoracic outlet.

Neurogenic TOS (NTOS), the most common form of TOC, can result from inadequate space caused byscalene hypertrophy, fibrosis, or congenital abnormalities, such as the occurrence of a cervical rib.Other causes include repetitive motions that can enlarge or change the tissue in or near the thoracicoutlet (similar to carpel tunnel syndrome). These repetitive activities include assembly line work, typing,and other movements; hyperextension-flexion injuries; neck injuries from motor vehicle accidents(whiplash); and sports-related injuries, particularly from swimming, baseball (pitching), weightlifting,and volleyball.

Frequent symptoms of NTOS include numbness; tingling in the fingers; pain in the neck, shoulder orarm; muscle spasms around the scapula; headaches; and weakness in the upper extremities (Table 1).2

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[3]

Pathophysiology

In many patients, the etiology of NTOS involves a combination of a double hit of a congenitalpredisposition and an injury to the area that compromises the outlet. The narrowed space affects thescalene muscles, the brachial plexus, the long thoracic and suprascapular nerves, and the stellateganglion (Figure 1).

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[4]

Although the notion of NTOS as a complex spectrum disorder provokes some controversy in the field, itsimpact on patients is beyond dispute. Data indicate that the quality of life for a patient with untreatedTOS is as impaired as that of someone with chronic heart failure.3

TOS has been divided into 3 forms:

Neurogenic TOS (brachial plexus compression)

1. True neurogenic TOS2. Common neurogenic TOS

Arterial (subclavian artery compression)Venous (subclavian vein compression)

As noted, nearly all cases of TOS (95%) are neurogenic in origin. NTOS is an underappreciated and oftenoverlooked cause of shoulder and neck pain and numbness. Like patients with other chronic painconditions, patients with untreated neurogenic TOS experience a diminished quality of life, reducedfinancial well-being, functional limitations, and an increased risk for depression and anxiety.4-6

True NTOS, which is confirmed with objective findings, accounts for only 1% of cases, whereas commonNTOS, which has symptoms suggestive of brachial plexus compromise but no objective findings, makesup 99% of neurogenic cases of TOS.7,8 The remaining cases of TOS are arterial (1%) and venous(3%-5%).1

Neurogenic TOS occurs in an estimated 3 to 80 per 1,000 individuals, the wide range reflecting the lackof confirmation in many patients with signs and symptoms indicative of the condition. Women withNTOS outnumber men by 3 to 4:1. The syndrome is particularly common in people who perform

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repetitive tasks with their upper extremities, such as violinists, data entry personnel, and workers onassembly lines. Athletes with repetitive overhead arm motion, including volleyball players, swimmers,baseball pitchers, and weightlifters, also are at increased risk, as are people who have experienced necktrauma.9

Histologic studies suggest that injury to either the anterior scalene muscle (ASM) or the middle scalenemuscle are the main causative factors of NTOS. Muscle fibrosis is a prime finding on examination ofexcised scalene muscles, with NTOS patients having 3 times as much scar tissue as unaffectedsubjects.8-10

The ASM derives from the transverse processes of the C3-C6 vertebrae. The muscle, which attaches tothe first rib, serves as an accessory muscle of respiration, and also rotates the neck slightly. Spasm ofthe ASM puts traction on the brachial plexus and causes edema of the muscle and nerves, which, inturn, limits the space of the outlet. Development of scar tissue and fibrosis of the ASM further worsenneural compromise and perpetuate pain.8,11

Targeting treatment to relieve tension and spasm of the ASM can interrupt the chain of events thatleads to NTOS.

Diagnosis

There is no one standard for the diagnosis of TOS. The diagnosis of NTOS can be difficult because itoften has a nonspecific clinical presentation. In a classic case, the patient will complain of painoriginating in the area of the shoulder and radiating along the inner aspect of the arm. Other commonsymptoms involve pain in the neck; the trapezius, mastoid, and anterior chest wall musclesall fromupper plexus compression (C5-C7). Physical examination will reveal tenderness in the scalene muscles,trapezius, and chest wall. Patients may have a positive Tinel sign over the brachial plexus in the neck,reduced sensation in the fingers to light touch, and positive provocative maneuvers.9

Complicating the differential diagnosis, however, is that the entire arm often is involved withoutdermatomal preference. The clinician must distinguish cervical radiculopathy from disk herniation orstenosis and rule out carpal tunnel syndrome.

A thorough history and physical examination are key to accurate diagnosis of NTOS. Testing for NTOS isunreliable. Ancillary testing lacks sensitivity and specificity. Similarly, provocative testing, including theAdson maneuver,12 has unknown reliability and specificity. The Adson maneuver, in particular, producesmany false positive results and no longer is considered useful for identifying patients with NTOS.13

Provocative maneuvers, nerve tension tests, and thumb pressure over the brachial plexus can assist inthe determination of NTOS, but the elevated arm stress test, or Roos stress test, is perhaps the mostreliable indicator.13 Another potentially useful diagnostic test includes the Spurling test to identifycervical disk disease.8,14,15

Imaging Studies

Patients with NTOS often have normal results on electromyelography (EMG) and nerve conduction tests.However, these studies can be used to exclude other causes of neuropathic symptoms, such asradiculopathy, carpal tunnel syndrome, cubital tunnel syndrome, and polyneuropathy.

A chest x-ray may be warranted to identify cases of cervical rib. Magnetic resonance imaging andcomputed tomography (CT) also can help to rule out conditions that mimic NTOS.

Some evidence suggests that a medial antebrachial cutaneous nerve conduction study can detectmilder cases of NTOS. This test measures sensory function of the lower trunk of the brachial plexus and

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often yields positive results in patients with negative findings on an EMG or nerve conduction tests.However, additional studies are required to validate the utility of the test.9,16

Anterior Scalene Block

First described in 1939, the anterior scalene block (ASB) is an intramuscular confirmatory test for NTOS.The block paralyzes the muscle in spasm, allowing the first rib to descend and decompresses thethoracic outlet.17 A positive response to an ASB test correlates well with good surgical outcomes,whereas temporary muscle relaxation helps predict benefit from decompression. In one study, EMG-guided block provided relief in 94% of patients who underwent surgery.18

A variety of imaging techniques can improve the success of ASB. CT guidance for scalene injections, inparticular, has been shown to minimize Horners sign, dysphonia, brachial plexus block, anddysphagia.17

Treatment

Conservative

Conservative treatment for NTOS involves steps to minimize pressure on the brachial plexus, restoringmuscle balance in the neck, and improving neural mobility. Correcting ergonomic issues and poorposture can help, as can nerve glides, stretching exercises, and biofeedback. A 14-month course ofpostural correction and strengthening of the shoulder girdle led to significant reductions in pain andhigh patient satisfaction in one study.19

Physical Therapy

Some data support the use of heat packs, exercise programs, and cervical traction for the treatment ofNTOS.20,21 A course of inpatient rehabilitation, followed by a home exercise program, appears to have ahigh rate of satisfaction among patients who have undergone this regimen. However, data suggest that,in general, no single approach to physical therapy is sufficient on its own. Indeed, without otherinterventions, physical therapy may lead to worse outcomes for some patients. In one study, 42 patients(37 women, 5 men) diagnosed with NTOS who had participated in physical therapy at least 6 monthsprior to the study were selected.22 At the end of the follow-up period, 25 patients reported symptomaticimprovement, 10 reported that they were the same, and 7 patients had worse symptoms. Poor overalloutcome was related to obesity (P


Chemodenervation

Injection of onobotulinum toxin Type A (Botox) is a relatively new and promising approach to thetreatment of NTOS.23 Studies indicate that onobotulinum toxin is safe and effective for an increasingnumber of neuromuscular ailments. Approved indications for onobotulinum toxin injections includehemifacial spasm, blepharospasm, strabismus, and chronic migraine, among others. Successful off-labeluse also has been described for lumbosacral myofascial pain, piriformis syndrome, and lateralepicondylitis.

Administration of onobotulinum toxin for NTOS involves a single, low-dose injection (20 units) into theASM under CT-guidance. In one study, 27 patients with NTOS experienced substantial pain relief for upto 3 months following low-dose injections of onobotulinum toxin under CT guidance.23 The primaryoutcome was pain and sensation on a visual analog scale (VAS) at 1, 2, and 3 months after therapy.Short Form McGill Pain Questionnaire scores were evaluated before treatment and at 1, 2, and 3 monthsafter therapy. Patients reported substantial relief from treatment at both 1 and 2 months, andstatistically and clinically significant relief in both sensory and VAS scores at the 3-month point (29%and 15%, respectively).23

Onobotulinum toxin reduces muscle overactivity in the area of the injection by blocking the release ofacetylcholine, weakening the muscle for as long as 3 to 4 months. The toxin also may reduce pain andinflammation in some patients, perhaps by inhibiting the release of neuropeptidesparticularlysubstance P and glutamatethat are implicated in nociceptive transmission and centralsensitization.24,25 Some evidence suggests that onobotulinum toxin can improve wound healing andreduce scarring in injured muscles.5,26

Injections of onobotulinum toxin represent a minimally invasive approach for patients hoping to avoidsurgery, or a bridge to surgery for those seeking to delay the procedure. Successful injections mayobviate the need for surgeryand the potential complications from surgeryand limit the time patientsmust take off from work, home duties, and other activities of daily living. This benefit can be substantialbecause the common course for surgical patients involves 8 weeks of physical therapy starting 2 weeksafter the procedure, necessitating 2 to 3 months leave from work, as well as no heavy lifting (>10pounds) for 6 months.5

Although chemodenervation can be performed using multiple imaging modalities, the evidence for CTguidance is strong (Table 2). CT allows clinicians to visualize nearby anatomy (in real-time in the case ofCT fluoroscopy), and, unlike ultrasound, it is not vulnerable to obscuring by adiposity or osseousstructures. CT imaging is fast, accurate, reliable, and safe, leading to a higher percentage of successfulanesthetic blocks compared to other modalities: 82% versus 38% for ultrasound, 18% for EMG +fluoroscopy, and 72% for EMG alone.17,27,28 This advantage is borne out by the high rate of improvementafter surgery associated with CT-guided blocks (70%) to confirm true cases of neurogenic TOS.5,23

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[5]

Keeping exposure time to 60 seconds or less limits the amount of ionizing radiation patients receive.

Surgical Decompression

Multiple approaches to surgical decompression for NTOS are available, although comparative efficacydata for the techniques do not exist. Studies suggest that initial rates of success are high, approaching90%; however, complications occur in more than 30% of patients and longitudinal data show a 60%recurrence of symptoms within the first year after surgery and 80% within the second year. In addition,60% of patients report persistent disability within the first year after surgery.29

Conclusion

Neurologic TOS is the most common type of TOS, as well as the most often overlooked andmisdiagnosed form of the condition. It causes persistent pain, impaired function, and emotional distress.If untreated, the quality of life for patients with NTOS is profoundly diminished. Emerging evidencesupports minimally invasive chemodenervation of the cervicothoracic musculature with onobotulinumtoxin. Clinicians and patients should consider this approach before attempting surgical decompression.References: References

1. Hooper TL, Denton J, McGalliard MK, Brisme JM, Sizer PS Jr. Thoracic outlet syndrome: acontroversial clinical condition. Part 1: anatomy, and clinical examination/diagnosis. J Man ManipTher. 2010;18(2):74-83.

2. Christo PJ, McGreevy K. Updated perspectives on neurogenic thoracic outlet syndrome. Curr PainHeadache Rep. 2011;15 (1):14-21.

3. Chang, DC, Rotellina-Coltvet LA, Mukherjee D, De Leon R, Freischlag JA. Surgical intervention forthoracic outlet syndrome improves patients quality of life. J Vasc Surg. 2009;49(3):630-635.

4. Institute of Medicine (US) Committee on Advancing Pain Research, Care, and Education. Relieving pain in America: a blueprint for transforming prevention, care, education and research.Washington, DC: National Academies Press (US); 2011.

5. Stewart WF, Ricci JA, Chee E, Morganstein D, Lipton R. Lost productive time and cost due tocommon pain conditions in the US workforce. JAMA. 2003;290(18):2443-2454.

6. Leong IY, Farrell MJ, Helme RD, Gibson SJ. The relationship between medical comorbidity and self-rated pain, mood disturbance, and function in older people with chronic pain. J Gerontol A BiolSci Med Sci. 2007;62(5):550-555.

7. Atasoy, E. Thoracic outlet compressionsyndrome. Orthop Clin North Am. 1996;27(2):265-303.

8. Brantigan CO, Roos DB. Etiology ofneurogenic thoracic outlet syndrome. Hand Clin. 2004;20(1);17-22.

9. Sanders RJ, Hammond SL, Rao NM.Thoracic outlet syndrome: a review. Neurologist. 2008;14(6):365-373.

10. Machleder HI, Moll F, Verity MA. The anterior scalene muscle in thoracic outlet compressionsyndrome. Histochemical and morphometric studies. Arch Surg. 1986;121(10):1141-1144.

11. Atasoy E. Thoracic outlet syndrome: anatomy. Hand Clin. 2004;20(1);7-14.12. Demirbag D, Unlu E, Ozdemir F, et al. The relationship between magnetic resonance imaging

findings and postural maneuver and physical examination tests in patients with thoracic outletsyndrome: results of a double-blind, controlled study. Arch Phys Med Rehabil. 2007;88(7):844-851.

13. Physiopedia. Roos stress test. http://www.physio-pedia.com/Roos_Stress_Test. Accessed August17, 2014.

14. Roos, DB. New concepts of TOS that explain etiology, symptoms, diagnosis and treatment. Vasc

Page 7 of 10


Surg. 1979;13:313-2115. Rayan GM, Jensen C. Thoracic outlet syndrome: provocative examination maneuvers in a typical

population. J Shoulder Elbow Surg. 1995;4(2):113-117.16. Foley JM, Finlayson H, Travlos A. A review of thoracic outlet syndrome and the possible role of

botulinum toxin in the treatment of this syndrome. Toxins. 2012;4(11):1223-1235.17. Mashayekh A, Christo PJ, Yousem DM, Pillai JJ. CT guided injection of the anterior and middle

scalene muscles: technique and complications. Am J Neuroradiol. 2011;32(3):495-500.18. Jordan SE, Machleder HI. Diagnosis of thoracic outlet syndrome using electrophysiologically

guided anterior scalene blocks. Ann Vasc Surg. 1998:12(3):260-264.19. Crosby CA, Wehbe MA. Conservative treatment for thoracic outlet syndrome. Hand Clin.

2004;20(1): 43-49.20. Taskaynatan MA, Balaban B, Yasar E, et al. Cerivcal traction in conservative management of

thoracic outlet syndrome. J Musculoskeletal Pain. 2007;15 (1): 89-94.21. Gulbahar S, Akalin E, Baydar M, et al. Regular exercise improves outcome in droopy shoulder

syndrome: a subgroup of thoracic outletsyndrome. J Musculoskeletal Pain. 2005;13(4):21-26.

22. Novak CB, Collins ED, Mackinnon SE. Outcome following conservative management of thoracicoutlet syndrome. J Hand Surg Am. 1995;20(4): 542-548.

23. Christo PJ, Christo DK, Carinici AJ, Freischlag FA. Single CT-guided chemodenervation of theanterior scalene muscle with botulinum toxin for neurogenic thoracic outlet syndrome. Pain Med.2010;11(4): 504-511.

24. Aoki K. Review of proposed mechanism for the antinociceptive action of botulinum toxin type A. Neurotoxicology. 2005;26(5):785-793.

25. Sheean G. Botulinum toxin for the treatment of musculoskeletal pain and spasm. Curr PainHeadache Rep. 2002;6(6):460-469.

26. Childers MK, Wilson DJ, et al. Treatment of painful muscle syndromes with botulinum toxin: Areview. J Musculoskel Rehab. 1998;10:89-96.

27. Torriani M, Gupta R, Donahue DM. Botulinum toxin injection in neurogenic thoracic outletsyndrome: results and experience using an ultrasound-guided approach. Skeletal Radiol.2010;39(10):973-980.

28. Jordan SE, Ahn SS, Gelabert HA. Combining ultrasonography and electromyography forbotulinum chemodenervation treatment of thoracic outlet syndrome: comparison withfluoroscopy and electromyography guidance. Pain Physician. 2007;10(4):541-546.

29. Franklin GM, Fulton-Kehoe D, Bradley C, Smith-Weller T. Outcome of surgery for thoracic outletsyndrome in Washington state workers compensation. Neurology. 2000;54(6):1252-1257.

View Sources [6] References

1. Hooper TL, Denton J, McGalliard MK, Brisme JM, Sizer PS Jr. Thoracic outlet syndrome: acontroversial clinical condition. Part 1: anatomy, and clinical examination/diagnosis. J Man ManipTher. 2010;18(2):74-83.

2. Christo PJ, McGreevy K. Updated perspectives on neurogenic thoracic outlet syndrome. Curr PainHeadache Rep. 2011;15 (1):14-21.

3. Chang, DC, Rotellina-Coltvet LA, Mukherjee D, De Leon R, Freischlag JA. Surgical intervention forthoracic outlet syndrome improves patients quality of life. J Vasc Surg. 2009;49(3):630-635.

4. Institute of Medicine (US) Committee on Advancing Pain Research, Care, and Education. Relieving pain in America: a blueprint for transforming prevention, care, education and research.Washington, DC: National Academies Press (US); 2011.

5. Stewart WF, Ricci JA, Chee E, Morganstein D, Lipton R. Lost productive time and cost due tocommon pain conditions in the US workforce. JAMA. 2003;290(18):2443-2454.

6. Leong IY, Farrell MJ, Helme RD, Gibson SJ. The relationship between medical comorbidity and self-rated pain, mood disturbance, and function in older people with chronic pain. J Gerontol A Biol

Page 8 of 10


Sci Med Sci. 2007;62(5):550-555.7. Atasoy, E. Thoracic outlet compressionsyndrome. Orthop Clin North Am. 1996;27(2):265-303.

8. Brantigan CO, Roos DB. Etiology ofneurogenic thoracic outlet syndrome. Hand Clin. 2004;20(1);17-22.

9. Sanders RJ, Hammond SL, Rao NM.Thoracic outlet syndrome: a review. Neurologist. 2008;14(6):365-373.

10. Machleder HI, Moll F, Verity MA. The anterior scalene muscle in thoracic outlet compressionsyndrome. Histochemical and morphometric studies. Arch Surg. 1986;121(10):1141-1144.

11. Atasoy E. Thoracic outlet syndrome: anatomy. Hand Clin. 2004;20(1);7-14.12. Demirbag D, Unlu E, Ozdemir F, et al. The relationship between magnetic resonance imaging

findings and postural maneuver and physical examination tests in patients with thoracic outletsyndrome: results of a double-blind, controlled study. Arch Phys Med Rehabil. 2007;88(7):844-851.

13. Physiopedia. Roos stress test. http://www.physio-pedia.com/Roos_Stress_Test. Accessed August17, 2014.

14. Roos, DB. New concepts of TOS that explain etiology, symptoms, diagnosis and treatment. VascSurg. 1979;13:313-21

15. Rayan GM, Jensen C. Thoracic outlet syndrome: provocative examination maneuvers in a typicalpopulation. J Shoulder Elbow Surg. 1995;4(2):113-117.

16. Foley JM, Finlayson H, Travlos A. A review of thoracic outlet syndrome and the possible role ofbotulinum toxin in the treatment of this syndrome. Toxins. 2012;4(11):1223-1235.

17. Mashayekh A, Christo PJ, Yousem DM, Pillai JJ. CT guided injection of the anterior and middlescalene muscles: technique and complications. Am J Neuroradiol. 2011;32(3):495-500.

18. Jordan SE, Machleder HI. Diagnosis of thoracic outlet syndrome using electrophysiologicallyguided anterior scalene blocks. Ann Vasc Surg. 1998:12(3):260-264.

19. Crosby CA, Wehbe MA. Conservative treatment for thoracic outlet syndrome. Hand Clin.2004;20(1): 43-49.

20. Taskaynatan MA, Balaban B, Yasar E, et al. Cerivcal traction in conservative management ofthoracic outlet syndrome. J Musculoskeletal Pain. 2007;15 (1): 89-94.

21. Gulbahar S, Akalin E, Baydar M, et al. Regular exercise improves outcome in droopy shouldersyndrome: a subgroup of thoracic outletsyndrome. J Musculoskeletal Pain. 2005;13(4):21-26.

22. Novak CB, Collins ED, Mackinnon SE. Outcome following conservative management of thoracicoutlet syndrome. J Hand Surg Am. 1995;20(4): 542-548.

23. Christo PJ, Christo DK, Carinici AJ, Freischlag FA. Single CT-guided chemodenervation of theanterior scalene muscle with botulinum toxin for neurogenic thoracic outlet syndrome. Pain Med.2010;11(4): 504-511.

24. Aoki K. Review of proposed mechanism for the antinociceptive action of botulinum toxin type A. Neurotoxicology. 2005;26(5):785-793.

25. Sheean G. Botulinum toxin for the treatment of musculoskeletal pain and spasm. Curr PainHeadache Rep. 2002;6(6):460-469.

26. Childers MK, Wilson DJ, et al. Treatment of painful muscle syndromes with botulinum toxin: Areview. J Musculoskel Rehab. 1998;10:89-96.

27. Torriani M, Gupta R, Donahue DM. Botulinum toxin injection in neurogenic thoracic outletsyndrome: results and experience using an ultrasound-guided approach. Skeletal Radiol.2010;39(10):973-980.

28. Jordan SE, Ahn SS, Gelabert HA. Combining ultrasonography and electromyography forbotulinum chemodenervation treatment of thoracic outlet syndrome: comparison withfluoroscopy and electromyography guidance. Pain Physician. 2007;10(4):541-546.

29. Franklin GM, Fulton-Kehoe D, Bradley C, Smith-Weller T. Outcome of surgery for thoracic outletsyndrome in Washington state workers compensation. Neurology. 2000;54(6):1252-1257.

First published on: September 1, 2014

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