Source: Diagnosing thoracic outlet syndrome
C.O. Brantigan, D.B. Roos, Hand Clin 20 (2004):27–36.

Thoracic outlet syndrome (TOS) is a common condition that is recognized uncommonly because the manifestations are varied and there is no single definitive test for it. Radiographs, MRIs, and even EMGs cannot make the diagnosis with certainty. Unfortunately many physicians doubt the diagnosis if the pathology cannot be seen radiographically or measured electrophysiologically.

Conceptually TOS is simple. It is a symptom complex caused by compression of the brachial plexus, or the axillary-subclavian artery or vein as they exit the chest. The clinical presentation is highly variable, depending on what parts of the brachial plexus are involved and to what extent the circulatory system is involved. The purely vascular forms of thoracic outlet syndrome are diagnosed easily but are uncommon. Neurologic compression is more difficult to diagnose. The physician needs to discern which symptoms relate to the brachial plexus, which relate to the major vessels, and which are totally unrelated. Because the presentation is so varied, each patient represents a challenge in physical diagnosis. Diagnosis is based on the total clinical picture, which is made up of a meticulous history, a complete physical examination, and a review of medical records.

As experience with this common though complicated disorder has increased, several basic concepts have emerged. Once these concepts are understood, it is possible to make an exact diagnosis and to plan specific, effective management.

Basic concepts of thoracic outlet syndrome

There is a mechanical predisposition.

People who develop clinical manifestations of TOS have one or more congenital anomalies that predispose them to develop symptoms. Thoracic outlet syndrome is a mechanical space problem. Because of the invariable underlying congenital anomalies and often a superimposed injury causing chronic muscle spasm, the space for the major structures of the outlet becomes compromised. This restriction of space precipitates the symptom complex of TOS. Treatment is directed to correcting the space problems either by physical therapy, exercise, or surgical decompression. The longer the space problem exists the more damage is done to the structures, particularly to the nerves of the brachial plexus.

TOS symptoms are primarily neurologic

In 98% of cases the symptoms are neurologic. Fifteen percent may have some concomitant arterial symptoms, but arterial symptoms seldom exist alone. Symptoms caused by pure venous compression occur in 1.5% of patients and usually present as axillary subclavian vein thrombosis. Physicians who diagnose only the vascular forms of thoracic outlet syndrome are misdiagnosing the vast majority of patients they see who have this neurologic condition.

Structural anomalies cause the problem

These abnormalities have been well described. Each has a specific effect and few of them compromise the circulation. For this reason, using circulatory tests as the basis for specific diagnosis commonly leads to error. Muscle spasm is important and aggravates the structural problems. Injuries lead to fibrosis, which further aggravates the structural problems.

Accurate diagnosis is based on the total clinical picture

There are no short cuts. A careful, even exhaustive history and physical examination are required, together with selective testing. Knowledge of other conditions that may belong in the domain of other specialists is required. When a patient presents with thoracic outlet syndrome symptoms, the goal should be to figure out an accurate diagnosis and not just to determine if thoracic outlet syndrome is present or absent. This may require a team of physicians and therapists.

Symptoms

TOS occurs in young and middle-aged adults and is three times as frequent in women as in men. Symptoms may develop spontaneously or following trauma of a type that causes chronic muscle spasm in the neck or shoulder region. [...] [Read More]

Source: Thoracic Outlet Syndrome
John T. Lohr PhD, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Medicine, 2002. Healthline.com.

Thoracic Outlet Syndromes

Definition

Thoracic outlet syndromes are a group of disorders that cause pain and abnormal nerve sensations in the neck, shoulder, arm, and/or hand.

Brachial Plexus. Image Credit: University of Bristol; Pen and ink drawing by PhD student Alice Roberts, Department of Anatomy

Description

The thoracic outlet is an area at the top of the rib cage, between the neck and the chest. Several anatomical structures pass through this area, including the esophagus, trachea, and nerves and blood vessels that lead to the arm and neck region. The area contains the first rib; collar bone (clavicle); the arteries beneath the collar bone (subclavian artery), which supply blood to the arms, a network of nerves leading to the arms (brachial plexus); and the top of the lungs.

Pain and other symptoms occur when the nerves or blood vessels in this area are compressed. The likelihood of blood vessels or nerves in the thoracic outlet being compressed increases with increased size of body tissues in this area or with decreased size of the thoracic outlet. The pain of thoracic outlet syndrome is sometimes confused with the pain of angina that indicates heart problems. The two conditions can be distinguished from each other because the pain of thoracic outlet syndrome does not appear or increase when walking, while the pain of angina does. Also, the pain of thoracic outlet syndrome usually increases if the affected arm is raised, which does not happen in cases of angina.

There are three types of thoracic outlet syndromes: (Cf. next excerpt, NINDS)

• True neurogenic thoracic outlet syndrome is caused by a compression of the nerves in the brachial plexus. Abnormal muscle or other tissue causes the problem.
  
• Arterial thoracic outlet syndrome is caused by compression of the major artery leading to the arm, usually by a rib.
  
• Disputed thoracic outlet syndrome describes patients who have chronic pain in the shoulders and arms and have no other disease or syndrome, but the underlying cause cannot be accurately determined.
• [Read More]

Source: NINDS Thoracic Outlet Syndrome Information Page
National Institute of Neurological Disorders and Stroke (NINDS) [Last updated 20.06.08]

What is Thoracic Outlet Syndrome?

TOS is an umbrella term that encompasses three related syndromes that cause pain in the arm, shoulder, and neck: neurogenic TOS (caused by compression of the brachial plexus), vascular TOS (caused by compression of the subclavian artery or vein) and nonspecific or disputed TOS (in which the pain is from unexplained causes).  Occasionally, neurogenic TOS and vascular TOS co-exist in the same person. Most doctors agree that TOS is caused by compression of the brachial plexus or subclavian vessels as they pass through narrow passageways leading from the base of the neck to the armpit and arm, but there is considerable disagreement about its diagnosis and treatment. Making the diagnosis of TOS even more difficult is that a number of disorders feature symptoms similar to those of TOS, including rotator cuff injuries, cervical disc disorders, fibromyalgia, multiple sclerosis, complex regional pain syndrome, and tumors of the syrinx or spinal cord.  Symptoms of TOS vary depending on the type.

Neurogenic TOS has a characteristic sign, called the Gilliatt-Sumner hand, in which there is severe wasting in the fleshy base of the thumb. There may be numbness along the underside of the hand and forearm, or dull aching pain in the neck, shoulder, and armpit.

Vascular TOS features pallor, a weak or absent pulse in the affected arm, which also may be cool to the touch and appear paler than the unaffected arm. Symptoms may include numbness, tingling, aching, and heaviness.

Non-specific TOS most prominently features a dull, aching pain in the neck, shoulder, and armpit that gets worse with activity. Non-specific TOS is frequently triggered by a traumatic event such as a car accident or a work related injury.  It also occurs in athletes, including weight lifters, swimmers, tennis players, and baseball pitchers.

TOS is more common in women. The onset of symptoms usually occurs between 20 and 50 years of age. Doctors usually recommend nerve conduction studies, electromyography, or imaging studies to confirm or rule out a diagnosis of TOS. [...] [Read More]

Source: Tests and diagnosis
Thoracic outlet syndrome, Mayo Clinic staff (8.11.08)

[...]
Some of the more common provocation tests that can suggest the presence of thoracic outlet syndrome include:

• Adson's maneuver. For this test, you'll be asked to turn your head toward the symptomatic shoulder while you extend your arm, neck and shoulder slightly away from your body. While you inhale, your doctor will check for a pulse on the wrist of your extended arm. If your pulse is diminished or if your symptoms are reproduced during the maneuver, your doctor considers this a positive test result, which may indicate thoracic outlet syndrome. Because false-positives often occur, your doctor may repeat the test on the unaffected side.
  
• Wright test. From a sitting position and with the help of your doctor, you'll hold your arm up and back (hyperabduction), rotating it outward, while your doctor checks your pulse to see if it's diminished. As in the Adson's maneuver, your doctor will want to know if your symptoms are reproduced during the test.
  
• Roos stress test. From a sitting position, your doctor will ask you to hold both elbows at shoulder height while pushing your shoulders back. You will then repeatedly open and close your hands for several minutes. If your symptoms are present after the test, or if you feel heaviness and fatigue in your shoulders, this can indicate the presence of thoracic outlet syndrome.

To confirm the diagnosis of thoracic outlet syndrome, your doctor may also order one or more of the following tests:

• X-ray. Your doctor may order an X-ray of the affected area, which may reveal an extra rib (cervical rib) and can also rule out other conditions that may be causing your symptoms.
  
• Magnetic resonance imaging (MRI) scan. MRI is a painless procedure that uses a magnetic field and radio waves to create computerized images of the soft tissues of your body. These images can help your doctor determine the location and cause of compressions of the brachial plexus nerves or the subclavian artery. The scans may also reveal any congenital anomalies — such as a fibrous band connecting your spine to your rib or a cervical rib — that may be the cause of your symptoms.
  
• Electromyography (EMG). This test enables your doctor to see and hear how your muscles and nerves are working. To conduct the test, a small electrode needle is inserted through your skin and into the muscles near where you're having symptoms. The electrical activity detected by this electrode is displayed on a monitor and may be heard through a speaker.
  
• Nerve conduction study. Also called nerve conduction velocity, this test measures the speed of conduction of impulses through a nerve. Doctors use the test to evaluate possible nerve damage. Small electrodes are placed on your skin over the area being tested, and a tiny electrical current is sent to the nerves in your thoracic outlet. The electrical signals produced by nerves and muscles are picked up by a computer, and the information is interpreted by a doctor trained in electrodiagnostic medicine.

• Read more...
• Definition • Symptoms • Causes • Complications • Preparing for your appointment
• Treatments and drugs • Lifestyle and home remedies • Coping and support • Prevention

Figure 1.
Compression factors in the thoracic outlet with the signs and symptoms produced.

Source: Urschel Jr. HC, Kourlis Jr. H. Thoracic outlet syndrome: a 50-year experience at Baylor University Medical Center Proc (Bayl Univ Med Cent) 2007;20:125–135.

Source: Diagnosing thoracic outlet syndrome
C.O. Brantigan, D.B. Roos, Hand Clin 20 (2004):27–36.

The most reliable test for TOS is the "elevated arm stress test," (EAST) described by Roos. It is performed by having the patient put both arms in the 90º
abduction–external rotation position, with the shoulders and elbows in the frontal plane of the chest. The patient is then instructed to open and close the hands slowly over a 3-minute period. Normally the patient can perform this stress test for 3 minutes with only forearm muscle fatigue and minimal distress. In those with an outlet syndrome, the test reproduces the usual symptoms: gradual increase of pain in the neck and shoulder, aching progressing down the arm, and paresthesias developing in the forearm and fingers. Those with arterial compression develop arm pallor with the arm elevated and reactive hyperemia when the limb is lowered. Those with venous compression may develop cyanosis and swelling. Many patients with TOS are unable to complete this test and drop the arms to the lap in marked distress, which they recognize as reproduction of their usual symptoms. An occasional patient with carpal tunnel syndrome may get some numbness in the fingers, but this is from compression of the median nerve during squeezing of the hand and is confined to the first three fingers, a different response from TOS. A patient with cervical disc syndrome may get pain in the neck and shoulder from holding the arms elevated but feels minimal distress in the arm or hand. A patient with orthopedic shoulder problems may experience intolerable symptoms but they are confined to the shoulder area. The important characteristics of a positive test include reproduction of usual symptoms that involve the entire extremity. The duration of tolerance of this test may reflect the severity of the TOS.

Nerve tension tests of the upper extremity have been described that correspond to straight leg raising as a test for nerve impingement in the lower extremity. Upper limb tension tests have been described that are median, ulnar, or radial nerve dominant. Although they may be well accepted by physiotherapists and do provide objective measurements, their role in separating TOS from other upper extremity nerve problems is not well documented. [...] [Read More]

See Also:
 NINDS Thoracic Outlet Syndrome Information Page
National Institute of Neurological Disorders and Stroke (NINDS)
 Physical Therapy Corner: Thoracic Outlet Syndrome

Source: Etiology and pathology
Richard J. Sanders, MD, Sharon L. Hammond, MD
Hand Clin 20 (2004):23–26

Etiology
Trauma
The etiology of neurogenic thoracic outlet syndrome (TOS) is believed to be a combination of neck trauma plus an anatomic predisposition. The basis for regarding neck trauma as the primary etiology stems from observations in most of a few thousand patients whose symptoms of pain in their necks and arms and paresthesia in their hands developed shortly after a motor vehicle accident. This observation was followed by microscopic studies that demonstrated significant histologic changes in the scalene muscles of patients with neurogenic TOS. Neck trauma may occur as a single acute incident or it can develop insidiously following repeated small episodes of neck strain.

Acute neck trauma
Motor vehicle accidents have a high incidence of whiplash injuries. This is the most common mechanism causing neurogenic TOS. More than half of the patients the authors see with neurogenic TOS developed their symptoms following a motor vehicle accident. Other investigators also have noted a high incidence of neck trauma. Studies of whiplash injuries following motor vehicle accidents by several authors revealed that more than 30% of these patients developed symptoms of neurogenic TOS; although most patients responded to conservative therapy, a fair number went on to surgical decompression of the thoracic outlet.

Repetitive stress and posture
The next most common cause of neurogenic TOS is repetitive stress injury in the work place. This develops in people who work at keyboards, on telephones, on assembly lines, or who sit in one position for several hours at a time. The specific cause is repeated small traumata to the neck muscles over a prolonged period of time either by frequently turning the neck back and forth, holding a telephone by bending the ear against the shoulder, or poor posture causing muscle imbalance. In muscle imbalance, some muscles are overused and others underused. TOS attributable to these causes frequently is associated with cumulative trauma syndrome, which includes carpal tunnel, pronator tunnel, radial tunnel, and cubital tunnel syndromes together with TOS. Support for the influence of posture on TOS symptoms comes from a survey of more than 1000 dentists, 98% of whom responded. In this group of dental practitioners, there was a 29% incidence of pain and paresthesia noted in the upper extremities. In a similar study of dental hygienists, 26% were noted to have symptoms of carpal tunnel syndrome. This emphasizes the importance of posture and position in the etiology and treatment of neuropathies caused by muscle imbalance or overuse. Other etiologies that may play a small role in causing neurogenic TOS are large, heavy breasts and carrying heavy backpacks. These causes are uncommon but do occur. [...] [Read More]

Brachial Plexus - Learning the Anatomy

Image Credit:
Medical Illustration and Photography, UNC Chapel-Hill, Medical Support
[University of North Carolina Medical School]

Ventral root of C5 Ventral root of C6 Ventral root of C7 Ventral root of C8 Ventral root of T1 Ulnar Radial Median Musculocutaneous Cords Medial Posterior Lateral Posterior divisions Anterior divisions Inferior Middle Superior Inferior trunk Middle trunk Superior trunk

Brachial Plexus Image Credit: DNA Illustrations, Inc. SparkCharts: The Nervous System : Brachial Plexus (2009)

Image Credit:
Anaesthesia UK (12.12.04): Applied anatomy for upper limb blocks


Image Credit:
Anaesthesia UK (12.12.04): idem.


Brachial Plexus Innervation (Rear aspect)
Image Credit: Peter Jurek © 2009, Right Brain Visualization Inc


Brachial Plexus Innervation (Frontal aspect)
Image Credit: Peter Jurek © 2009, Right Brain Visualization Inc

• Brachial Plexus
  Henry Gray (1825–1861). Anatomy of the Human Body. 1918. Fig. 808
  
• Brachial Plexus Anatomy
  Illustrated Notes in Regional Anesthesia
  
• Learn the Brachial Plexus in Five Minutes or Less
  Daniel S. Romm MD and Dennis A. Chu MD, Department of Veteran's Affairs, Biloxi, Mississippi
  
• Lecture 15: Muscles of the Appendicular Skeleton I
  Anthony Uzwiak, Anatomy and Physiology, Rutgers
• Use Google or Yahoo! to search for additional images:
   

Source:
Thoracic Outlet Syndrome
eMedicine, WebMD (Updated: 1.07.09)
Benjamin M Sucher, DO, FAAPMR, FAOCPMR,
Medical Director, EMG Labs of AARA (Arizona Arthritis & Rheumatology Associates)

Background
Thoracic outlet syndrome (TOS) is a controversial topic in the literature; many proponents support the existence of the condition, but some strongly vocal opponents doubt the validity of TOS as a medical entity. Even the name itself has been questioned because the actual site of pathology is technically the thoracic "inlet," not the "outlet." The primary controversy seems to center around the lack of objective criteria for diagnosis and the confusion with multiple types or clinical presentations.

Since TOS involves proximal neurovascular structures (see image below and Image 1), symptoms often are confused with various distal compression neuropathies or cervical radiculopathies. In addition, surgical treatment has been known to have devastating complications, which further fuels debate with the opponents of recognition of this entity. Conservative treatment appears to be the most universally accepted approach, with even surgeons recommending a prolonged trial before any operative procedure.

Image Credit: eMedicine, Thoracic Outlet Syndrome, BM Sucher, drawing by Travis Progressive postural decompensation with neurovascular compression. Normal resting posture. Shoulder protraction beginning; the sternomastoid muscles are shortening, drawing the head anteriorly and inferiorly. Advanced deformity with adaptive shortening of scalene and pectoralis minor muscles. Also note narrowed costoclavicular space (ribs 1-5 have been relatively elevated). Neurovascular compression is evident at all 3 sites.

Pathophysiology
Thoracic outlet syndrome (TOS) involves compression, injury, or irritation to the neurovascular structures at the root of the neck or upper thoracic region, bounded by the anterior and middle scalenes; between the clavicle and first rib (with possible enlargement/hypertrophy of the subclavius); or beneath the pectoralis minor muscle. Some authors define the thoracic outlet as an opening bordered by the first rib laterally, the vertebral column medially, and the claviculomanubrial complex anteriorly. The syndrome of compression at this site could be primarily neurologic, involving the brachial plexus, most often the lower trunk or medial cord; alternatively, it could involve compression of the subclavian artery and/or vein.

One proposed classification system has broken TOS into the following 3 categories:

• True neurogenic TOS: The brachial plexus is injured in these cases as documented by electromyography (EMG) and/or nerve conduction studies.
• True vascular TOS: The subclavian artery and/or vein is damaged or thrombosed, as documented by arteriogram or venogram.^1,2
• Nonspecific or disputed TOS: Patients have symptoms, but there are no abnormal tests to document the lesion clearly. This category is by far the most common type of TOS seen in the clinical setting.

Many authors have discovered accessory cervical ribs associated with TOS³; however, they have noted tough fibrous bands coming off the accessory ribs that are believed to be more responsible for the pathology. There have even been reports of bony fusion of variant cervical ribs, resulting in bifid ribs with attached fibrous bands.⁴ The bands cause tethering of the brachial plexus, which results in traction and, therefore, symptoms. Other authors report compression or irritation of the neurovascular bundle more distally under the pectoralis minor muscle or from anterior displacement of the humeral head.

Additionally, clavicle fractures can result in plexopathy from expanding hematomas or pseudoaneurysms that compress the plexus, with variable latent periods following the fracture. Delayed onset of symptoms may suggest exuberant callus from the healing fracture site. Nonunion of the fracture site also can result in direct compression by the lateral fragment, which is pulled inferiorly.

Trapezius weakness due to spinal accessory nerve injury (following cervical lymph node biopsy) also has been implicated as a cause of TOS. This results in "droopy shoulder" with secondary compression of the neurovascular bundle, which is particularly aggravated with arm elevation (abduction).⁵

• Overview • Differential Diagnoses & Workup • Treatment & Medication • Follow-up • Multimedia

References

1. de Leon RA, Chang DC, Hassoun HT, et al. Multiple treatment algorithms for successful outcomes in venous thoracic outlet syndrome.
   Surgery. May 2009;145(5):500-7. [Medline].
2. Davidovic LB, Koncar IB, Pejkic SD, et al. Arterial complications of thoracic outlet syndrome.
   Am Surg. Mar 2009;75(3):235-9. [Medline].
3. Brewin J, Hill M, Ellis H. The prevalence of cervical ribs in a London population.
   Clin Anat. Apr 2009;22(3):331-6. [Medline].
4. Cagli K, Ozcakar L, Beyazit M, et al. Thoracic outlet syndrome in an adolescent with bilateral bifid ribs.
   Clin Anat. Sep 2006;19(6):558-60. [Medline].
5. Al-Shekhlee A, Katirji B. Spinal accessory neuropathy, droopy shoulder, and thoracic outlet syndrome.
   Muscle Nerve. Sep 2003;28(3):383-5. [Medline].

Source:
The Thoracic Outlet Syndrome
Annie S. Dubuisson, MD
Department of Neurosurgery, CHU Liege, Belgium
(Dr. Dubuisson was a peripheral nerve fellow at LSUMC) Emphasis added.

Abstract:
Thoracic outlet syndrome (TOS) is due to compression/irritation of brachial plexus (BP) elements ("neurogenic TOS") and/or subclavian vessels ("vascular TOS") in their passage from the cervical area toward the axilla. The usual site of entrapment is the interscalenic triangle. TOS is a source of disagreement among clinicians regarding its incidence, diagnostic criteria and optimal treatment. Constitutional factors, like a cervical rib, predispose to the development of TOS. The syndrome often develops during the 3rd or 4th decade, following external factors such as trauma, weight excess, incorrect shoulder posture. The clinical picture can be varied: pain in the cervical region and arm, paresthesias (medial side of arm predilected) aggravated by overhead positions of the arms, hand intrinsic muscle deficit/atrophy, easy fatiguability, paleness, coldness of hand. The clinical examination may be entirely normal or show cervical muscle spasm, tenderness of BP in the supraclavicular area, radial pulse attenuation and occurence of symptoms upon positional maneuvers, sensory or motor deficit. The diagnosis is based upon clinical evaluation and absence of other relevant pathology. Therefore, the cervical spine and distal peripheral nerves are studied by radiological and electrophysiological studies. There is no laboratory test confirming TOS: most of the time, there is no anatomic variation seen radiologically and electrophysiological testing is normal. The scalene muscle block appears a helpful diagnostic tool if used with the other clinical data.

Unless there is significant motor deficit or subclavian artery compression, the treatment should be kept conservative as long as possible, by an individually tailored physical therapy program. In case of neurological deficit or symptoms unresponsive to medical treatment, the patients will be helped by decompressive operation in the thoracic outlet. Transaxillary first rib resection (TAR) has been the most popular surgical approach but nowadays, the supraclavicular approach has superseded TAR in many centers. The anterior approach provides a good access to the BP elements and subclavian artery, allowing their adequate relief from constrictive/irritative anatomic structures. The posterior subscapular approach is indicated in rare cases of TOS associated with severe obesity, a large cervical rib or recurrent TOS with residual first rib following TAR. (NerveCenter 4(2), 1999)

[...]
Epidemiology:
TOS commonly develops during the 3rd or 4th decade, more often in women, under the combination of a peculiar cervical anatomy and of external factors. Some morphotypes predispose to the syndrome: poor muscular development, droop of scapula, obesity and breast hypertrophy. The patient psychological status may sometimes play an important role in the development of the syndrome: stress and depression can lead to chronic muscle spasm in the neck region and there to decompensation of a previously asymptomatic predisposing anatomy. Other precipitating factors are work-related (static work posture). An antecedent of neck or shoulder trauma is noted in approximately half of the cases. [...] [Read Full Text]

Management plan flowchart for TOS