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Published online before print March 13, 2003, 10.1148/radiol.2272012111
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(Radiology 2003;227:461-468.)
© RSNA, 2003

Thoracic Imaging

Thoracic Outlet: Assessment with MR Imaging in Asymptomatic and Symptomatic Populations1

Xavier Demondion, MD, Eric Bacqueville, MD, Christelle Paul, MD, Bernard Duquesnoy, MD, Eric Hachulla, MD and Anne Cotten, MD

1 From the Departments of Osteoarticular Radiology (X.D., E.B., C.P., A.C.) and Rheumatology (B.D.), Hôpital Roger Salengro, Centre Hospitalier Regional Universitaire de Lille, Boulevard du Pr. J. Leclercq, 59037 Lille, France; Anatomy Laboratory, Faculty of Medicine, Université de Lille 2, France (X.D.); and Department of Internal Medicine, Hôpital Claude Huriez, Lille, France (E.H.). Received January 2, 2002; revision requested February 28; final revision received August 19; accepted August 27. Address correspondence to X.D. (e-mail: xdemondion@chru-lille.fr).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To compare the dynamic modifications of the thoracic outlet in asymptomatic volunteers and symptomatic patients and assess the presence and location of vasculonervous compressions in these two populations.

MATERIALS AND METHODS: Thirty-five healthy volunteers and 54 patients with clinical symptoms of thoracic outlet syndrome (TOS) underwent magnetic resonance (MR) imaging of the thoracic outlets with their arms alongside their bodies and after a postural maneuver. Measurements were obtained at the interscalene triangle (thickness of anterior scalene muscle, interscalene angle), at the costoclavicular space (minimum costoclavicular distance, distance between inferior border of subclavius muscle and the anterior chest wall, maximum thickness of subclavius muscle, angle between first rib shaft and horizontal), and at the retropectoralis minor space (distance between posterior border of pectoralis minor muscle and posterior lining of axilla at the passage of the axillary vessels, thickness of pectoralis minor muscle). The presence and location of vasculonervous compressions were also assessed. Group data were analyzed with the Student t test.

RESULTS: Patients with TOS had a smaller costoclavicular distance after the postural maneuver (P < .001), a thicker subclavius muscle in both arm positions (P < .001), and a wider retropectoralis minor space after the postural maneuver (P < .001) than did volunteers. Venous compressions after the postural maneuver were observed in 47% of volunteers and 63% of patients at the prescalene space, in 54% of volunteers and 61% of patients at the costoclavicular space, and in 27% of volunteers and 30% of patients at the retropectoralis minor space. Arterial and nervous compressions, respectively, were seen in 72% and 7% of patients. No arterial or nervous compression was seen in volunteers. Except for venous thrombosis, vasculonervous compressions were demonstrated only with arm elevation. Only three thoracic outlet measurements differed significantly in both populations.

CONCLUSION: MR imaging appeared helpful in demonstrating the location and cause of arterial or nervous compressions.

© RSNA, 2003

Index terms: Arteries, MR, 91.12941, 942.12941 • Arteries, subclavian, 942.781 • Thorax, diseases, 60.781 • Veins, MR, 91.12941, 942.12941 • Veins, subclavian, 942.781


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
The thoracic outlet consists of three anatomic spaces, the congenital or acquired narrowing of which may induce vascular or nervous compression. These spaces include the interscalene triangle, the costoclavicular space, and the retropectoralis minor space (subcoracoid tunnel) (1). Compression of neural, arterial, or venous structures when they cross one of these tunnels leads to thoracic outlet syndrome (TOS). The diagnosis is based on results of clinical evaluation, particularly if patient symptoms can be reproduced when various dynamic maneuvers, including elevation of the arm, are undertaken (2–4).

However, clinical diagnosis is often difficult, requiring the use of imaging procedures. The contribution of magnetic resonance (MR) imaging to the depiction of vasculonervous compression of the thoracic outlet has been outlined (5–7). Two case reports have indicated the usefulness of MR imaging in the assessment of vasculonervous compression after upper limb hyperabduction (8,9), and a more recent report has outlined the dynamic modifications of the costoclavicular space at MR imaging (10). However, to the best of our knowledge, there has been no large series in which volunteers and patients with TOS were compared, and we still do not know whether MR imaging demonstrates different features in these two populations. The purposes of our study were to compare the dynamic modifications of the thoracic outlet in asymptomatic volunteers and in symptomatic patients for the three compartments of the thoracic outlet at MR imaging and to assess the presence and location of vasculonervous compressions at MR imaging in these two populations.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Study Population
This prospective study incorporated analysis of results of MR examinations of 35 volunteers (10 men, 25 women; mean age, 36 years; age range, 21–49 years) and of 54 patients (eight men, 46 women; mean age, 39 years; age range, 20–59 years). The institutional review board of Centre Hospitalier Regional Universitaire de Lille approved the study, and informed consent was obtained from both volunteers and patients.

The volunteers and patients were asked to indicate which arm was the dominant one. None of the volunteers had thoracic outlet symptoms—in any arm position—or a history of trauma or neoplasm. The symptoms were on the dominant arm side in 37 patients and on the contralateral arm side in 17. All patients were evaluated by using provocative clinical tests (Adson maneuver [11], Wright maneuver [12], Eden maneuver or military position [13], Roos test [14], and Tinel sign in the supraclavicular fossa). Patients were included in the study when at least two provocative clinical tests reproduced the symptoms. The symptomatology of each patient was then classified by two clinicians (B.D., E.H.) as either arterial (ischemia, pallor, coolness, fatigability, pain, muscle cramp, pulselessness), venous (edema, cyanosis, fatigability, heaviness, thrombosis), neurologic (paresthesia, numbness, tingling, progressive weakness, loss of dexterity, pain), or neuroarterial (a combination of arterial and neurologic symptoms). Cervical signs were not prominent in any patient and could not explain the symptoms. Conventional radiography of the cervical spine was performed in patients with arterial or neuroarterial symptoms to detect cervical ribs and elongated transverse processes.

MR Imaging
The study was performed with a 1.5-T MR imaging unit (Magnetom Vision; Siemens, Erlangen, Germany) and a phased-array body coil. A coronal scout image was obtained initially. Two contiguous sagittal T1-weighted spin-echo sequences of 16 sections each were performed in the right and left thoracic outlets of each volunteer. For patients, only the symptomatic side was assessed to avoid prolonged uncomfortable positioning. Imaging parameters were as follows: repetition time msec/echo time msec, 544/14; section thickness, 3 mm; intersection gap, 0.3 mm; imaging matrix, 224 x 256; and field of view, 263 x 350 mm. The sequences were performed first with the subjects’ arms alongside the body and again after a postural maneuver (hyperabduction to 130° and external rotation of the arms). Each sagittal T1-weighted sequence took 4 minutes 7 seconds to perform. The length of time it took to perform an examination with the two arm positions, including the time involved in positioning the patient, was about 30 minutes.

An additional sequence with the same parameters was performed in the frontal plane in one patient.

Image Analysis
The anatomic characteristics of the thoracic outlet were analyzed by two experienced musculoskeletal radiologists (X.D., E.B.), who reviewed the images in consensus for the location of bone, vascular, and muscular structures, and who worked together at the console of the MR imaging unit to perform measurements at the interscalene triangle, the costoclavicular space, and the retropectoralis minor space before and after the postural maneuver. They were blinded as to whether they were reading MR images from volunteers or from patients.

Measurements at the interscalene triangle.—The interscalene angle—defined by the anterior scalene muscle and the middle and posterior scalene muscles—was measured (Fig 1). The thickness of the anterior scalene muscle at its widest part was also assessed (Fig 1).



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  		Figure 1. Sagittal T1-weighted MR image (544/14) of the interscalene triangle obtained in a 32-year-old male volunteer after hyperabduction of the arm shows the clavicle (1), the subclavian artery (2), the maximum thickness of the anterior scalene muscle (3), the middle and posterior scalene muscles (4), and the interscalene angle ({star} between the two white lines).

 
Measurements at the costoclavicular space.—Using the sagittal view that depicted the longest portion of the first rib shaft, the radiologists measured the following at the costoclavicular space: the minimum costoclavicular distance (ie, the minimum distance between the posterior border of the clavicle and the superior margin of the first rib), the distance between the inferior border of the subclavius muscle and the anterior chest wall, the maximum thickness of the subclavius muscle, and the angle between the axis of the longest portion of the first rib shaft and horizontal (Fig 2).



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  		Figure 2a. Sagittal T1-weighted MR images (544/14) of the costoclavicular space in a 41-year-old female volunteer obtained (a) with the arm alongside the body and (b) after hyperabduction of the arm show the clavicle (1), the subclavian artery (2), the subclavian vein (3), the angle ({star} in a) between the axis of the first rib and horizontal, the maximum thickness of the subclavius muscle (line at 4), and the minimum costoclavicular distance (line between 1 and 5).

 


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  		Figure 2b. Sagittal T1-weighted MR images (544/14) of the costoclavicular space in a 41-year-old female volunteer obtained (a) with the arm alongside the body and (b) after hyperabduction of the arm show the clavicle (1), the subclavian artery (2), the subclavian vein (3), the angle ({star} in a) between the axis of the first rib and horizontal, the maximum thickness of the subclavius muscle (line at 4), and the minimum costoclavicular distance (line between 1 and 5).

 
Measurements at the retropectoralis minor space.—In this area, the radiologists measured the distance between the posterior border of the pectoralis minor muscle and the posterior lining of the axilla at the passage of the axillary vessels. Because of the obliquity of the pectoralis minor muscle when the arms were alongside the body, this measurement was performed on the section in which the most lateral part of the muscle was imaged in order to be as near as possible to the insertion of the pectoralis minor muscle in the coracoid process (Fig 3a). After hyperabduction of the arm, this measurement was performed on the section in which the insertion of the pectoralis minor muscle was demonstrated because of the sagittalization of the muscle (Fig 3b). The thickness of the pectoralis minor muscle at its widest part was also assessed for both arm positions.



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  		Figure 3a. Sagittal T1-weighted MR images (544/14) of the retropectoralis minor space in a 37-year-old female volunteer obtained (a) with the arm alongside the body and (b) after hyperabduction of the arm show the pectoralis minor muscle (1), the coracoid process (2), and the distance (line at 3) between the posterior border of the pectoralis minor muscle and the anterior chest wall at the passage of the axillary vessels.

 


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  		Figure 3b. Sagittal T1-weighted MR images (544/14) of the retropectoralis minor space in a 37-year-old female volunteer obtained (a) with the arm alongside the body and (b) after hyperabduction of the arm show the pectoralis minor muscle (1), the coracoid process (2), and the distance (line at 3) between the posterior border of the pectoralis minor muscle and the anterior chest wall at the passage of the axillary vessels.

 
The radiologists were also asked to assess compression of the vessels and the brachial plexus at the different tunnels of the cervicothoracobrachial junction. They also assessed compression of the subclavian vein at the prescalene space (the space between the posterior border of the clavicle and the anterior border of the anterior scalene muscle), because this structure is not located in the interscalene triangle (7). The criterion used for determining whether a vessel was compressed was the appearance of a reduction in its cross-sectional area. Compression was defined as a cross-sectional area that was reduced more than 30% for arteries and more than 50% for veins. The criterion used for determining neurologic compression was the disappearance of the fat surrounding the brachial plexus or the appearance of a close relationship between the brachial plexus and adjacent bone structures.

Finally, the radiologists analyzed the conventional radiographs of the patients to detect cervical ribs and elongated transverse processes. They then compared the radiographs and MR images to verify that they had previously correctly recognized these abnormal features.

Statistical Analysis
All data were expressed in means ± SDs. Group data were analyzed with the Student t test. P < .05 was considered to indicate a statistically significant difference.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
The results of all the MR examinations could be used for analysis in our study. Thirty-four (63%) of the 54 patients presented with neuroarterial symptoms; 13 (24%), neurologic symptoms; four (7%), venous symptoms; and three (6%), arterial symptoms. Radiographs of the cervical spine obtained in 37 of the 54 patients demonstrated 10 elongated transverse processes of C7 and five cervical ribs. All of these structures were seen on MR images.

Interscalene Triangle
Measurements.—Results of measurements performed at the interscalene triangle are summarized in Tables 1–3. No significant difference was demonstrated between the measurements obtained in volunteers and those obtained in patients (Table 4).


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  		TABLE 1. Mean Values ± SDs and P Values for Measurements in 35 Volunteers

 

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  		TABLE 2. Mean Values ± SDs and P Values for Measurements in 54 Patients

 

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  		TABLE 3. Mean Values and P Values for Measurements in Men and Women among the 54 Patients

 

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  		TABLE 4. P Values for Difference in Measurements between 35 Volunteers and 54 Patients according to Arm Position

 
Vasculonervous compressions.—No arterial or nervous compression was observed at the interscalene triangle in the volunteers, but 33 venous compressions (47% of 70 subclavian veins) were observed in the prescalene space on MR images obtained in the volunteers after the postural maneuver.

Compression of the subclavian artery was seen at MR imaging in 11 patients (20%). In four of these 11 patients, this arterial compression was caused by a fibrous band. The fibrous band was associated with a cervical rib in two cases and with an elongated transverse process in one case (Fig 4). The fibrous bands were confirmed at surgery in two cases. Surgery was not performed in the other two cases.



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  		Figure 4a. (a) Sagittal and (b) coronal T1-weighted MR images (544/14) of the interscalene triangle obtained after hyperabduction of the arm in a 42-year-old female patient who had neuroarterial symptoms in the upper arm. Note that the subclavian artery (arrow) is compressed and lifted up by a tiny fibrous structure (arrowhead); this finding was confirmed at surgery.

 


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  		Figure 4b. (a) Sagittal and (b) coronal T1-weighted MR images (544/14) of the interscalene triangle obtained after hyperabduction of the arm in a 42-year-old female patient who had neuroarterial symptoms in the upper arm. Note that the subclavian artery (arrow) is compressed and lifted up by a tiny fibrous structure (arrowhead); this finding was confirmed at surgery.

 
Compression of the inferior trunk of the brachial plexus was also demonstrated at MR imaging in two patients (4%) who had a very tight interscalene triangle space. Compression of the subclavian vein in the prescalene space was demonstrated in 34 patients (63%).

Costoclavicular Space
Measurements.—Results of measurements performed at the costoclavicular space are summarized in Tables 1–3. The minimum costoclavicular distance became significantly more narrow (P < .001) in patients than in volunteers when the arms were elevated (Table 4). The distance between the posterior border of the subclavius muscle and the anterior chest wall narrowed significantly (P < .001) in both populations after the postural maneuver, but no significant difference in the degree of narrowing was demonstrated between the two populations. The thickness of the subclavius muscle decreased significantly after the postural maneuver in both populations, but the subclavius muscle was significantly thicker in the patients in both arm positions (Tables 1, 2, 4). The angle between the first rib axis and horizontal narrowed significantly after the postural maneuver in each population (Tables 1, 2), but no significant difference was found between the two populations (Table 4). Higher values for this angle were found in women with the arms alongside the body.

Vasculonervous compressions.—MR images obtained in the costoclavicular space after the postural maneuver revealed compression of 38 (54%) of the 70 subclavian veins that were assessed in the volunteers. No compression of the subclavian artery and brachial plexus was seen in volunteers.

Venous and arterial compressions (Fig 5), respectively, were demonstrated in 33 (61%) and 28 (52%) of the patients after the postural maneuver. A very tight contact between the subclavian artery and the extremity of a cervical rib was demonstrated in two patients after the postural maneuver. A subclavian vein thrombosis with a collateral pathway was demonstrated in one patient (Fig 6). A brachial plexus compression due to tight contact between the clavicle and the first rib was demonstrated in two patients (Fig 7).



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  		Figure 5a. Sagittal T1-weighted MR images (544/14) of the costoclavicular space in 35-year-old female patient with arterial symptoms obtained (a) with arms alongside the body and (b) after hyperabduction of the arms. Hyperabduction results in compression of the subclavian artery (arrow).

 


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  		Figure 5b. Sagittal T1-weighted MR images (544/14) of the costoclavicular space in 35-year-old female patient with arterial symptoms obtained (a) with arms alongside the body and (b) after hyperabduction of the arms. Hyperabduction results in compression of the subclavian artery (arrow).

 


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  		Figure 6a. Sagittal T1-weighted MR images (544/14) of (a) the costoclavicular space and (b) the retropectoralis minor space obtained after hyperabduction of the arms in a 33-year-old male patient with venous symptoms. Note the collateral venous pathways (arrows), a consequence of subclavian vein thrombosis.

 


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  		Figure 6b. Sagittal T1-weighted MR images (544/14) of (a) the costoclavicular space and (b) the retropectoralis minor space obtained after hyperabduction of the arms in a 33-year-old male patient with venous symptoms. Note the collateral venous pathways (arrows), a consequence of subclavian vein thrombosis.

 


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  		Figure 7a. Sagittal T1-weighted MR images (544/14) of the costoclavicular space in a 46-year-old female patient with neurologic symptoms obtained (a) with arms alongside the body and (b) after hyperabduction of the arms. Note the narrowness of the costoclavicular space, the contact between the clavicle and the cords of the brachial plexus (arrow), and the disappearance of the surrounding fat after arm hyperabduction (compare with Fig 2b).

 


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  		Figure 7b. Sagittal T1-weighted MR images (544/14) of the costoclavicular space in a 46-year-old female patient with neurologic symptoms obtained (a) with arms alongside the body and (b) after hyperabduction of the arms. Note the narrowness of the costoclavicular space, the contact between the clavicle and the cords of the brachial plexus (arrow), and the disappearance of the surrounding fat after arm hyperabduction (compare with Fig 2b).

 
Retropectoralis Minor Space
Measurements.—Results of measurements performed at the retropectoralis minor space are summarized in Tables 1–3. There was significant narrowing of the retropectoralis minor space after the postural maneuver in both populations (Tables 1, 2). However, this space was found to be significantly wider in patients after the postural maneuver (Tables 1, 2). The thickness of the pectoralis minor muscle increased significantly after the postural maneuver in the two populations (Tables 1, 2, 4).

Vasculonervous compressions.—MR images obtained in the retropectoralis minor space after the postural maneuver revealed compression of the axillary vein in 19 (27%) of the 70 veins that were assessed in the volunteers and in 16 (30%) of the patients themselves. No arterial or nervous compression was evidenced at this compartment in either population.

MR imaging revealed three arterial compressions in the three patients with arterial symptoms. In the 13 patients with neurologic symptoms, MR imaging depicted four brachial plexus compressions and seven arterial compressions; MR imaging results were considered normal in two cases. In the 34 patients with neuroarterial symptoms, MR imaging demonstrated 26 arterial compressions and findings that were considered normal in eight cases. In the four patients with venous symptoms, MR imaging demonstrated one case of venous thrombosis and three cases of arterial and venous compression. Overall, for the 54 patients with TOS, MR imaging demonstrated a vascular or nervous compression in 44 (81%).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
REFERENCES
 
Diagnosis of TOS is typically based on clinical and electrophysiologic criteria, such as results of electromyography or somatosensory evoked potential testing. However, in many cases symptoms are vague and nonspecific, and imaging is required to identify a cause and location to provide information for eventual surgical repair. The usefulness of spiral computed tomography (CT) in the evaluation of patients with TOS has been suggested, and functional anatomic imaging of the thoracic outlet with spiral CT has been reported (15,16). However, CT remains an imaging technique that requires irradiation and use of iodinated x-ray contrast media. More recently, MR imaging has been found to be useful in delineating the vasculonervous structures of this space. However, to the best of our knowledge, no results of studies involving large series of patients to determine whether MR imaging is valuable in the depiction of TOS have yet been published. Consequently, the purpose of our study was to evaluate whether MR imaging may demonstrate features suggestive of TOS.

Several provocative clinical tests that are important for making the diagnosis of TOS involve hyperabduction of the arm. This maneuver has recently been performed in patients imaged with MR. The first objective of this study was to analyze whether this maneuver allows depiction of different dynamic modifications of the thoracic outlet in volunteers and patients.

Dynamic modifications of the interscalene triangle space have not been reported in subjects examined with MR imaging, to the best of our knowledge. In our study, no significant difference in measurements could be demonstrated between volunteers and patients with TOS. Measurements at this space consequently appear not to be helpful in the differentiation of symptomatic from asymptomatic populations.

We observed a significant narrowing of the costoclavicular space after the postural maneuver in both populations, but the minimum costoclavicular distance narrowed to a significantly greater degree in patients than in volunteers. These results are in agreement with those of the study of Smedby et al (10), which was performed with 10 volunteers and seven patients. However, we did not obtain similar measurements. This discrepancy may be explained in part by the different degrees of arm abduction used (130° in our study; 90° in the study of Smedby et al [10], because they used an open MR imaging unit).

Hyperabduction of the arms produced horizontality of the first rib in both populations in our cohort. We observed a significantly higher degree of obliquity of the first rib in the female patients compared with the male patients. This finding may play a part in explaining the higher prevalence of TOS in women. Indeed, in accordance with observations in the literature (2), in our study, TOS was more frequent in women than in men (male-to-female ratio, 4:23). The results of this study also demonstrated that the subclavius muscle was thicker in the symptomatic population in both arm positions. This muscle modification highlights the potential importance of the subclavian muscle in compression of the subclavian vessels at the costoclavicular space.

Hyperabduction of the arm produced a narrowing of the retropectoralis minor space and a thickening of the pectoralis minor muscle in both populations. However, we found a greater distance between the posterior side of the pectoralis minor muscle and the anterior chest wall in the symptomatic population. We have no explanation for this paradoxic result. However, we did not observe any arterial or nervous compression in this space in either population.

The second objective of this study was to assess the presence of vasculonervous compressions in these two populations. Of interest is that all the vasculonervous compressions were demonstrated only when the arms were elevated; this fact highlights the usefulness of this postural maneuver when a patient is suspected of having TOS. Venous compression was frequently demonstrated in the three compartments of the thoracic outlet in both asymptomatic and symptomatic populations when the arms were elevated. Venous compression has already been reported in asymptomatic populations imaged with color duplex ultrasonography (US) (17,18), phlebography (19), and CT (16) when the arms are elevated. This feature must consequently be interpreted carefully in patients with symptoms of TOS. Venous thrombosis and collateral circulation were detected with both arm positions. They represent an objective, but probably delayed, feature of venous compression.

In our study, arterial compression was demonstrated in 39 patients (72%). Arterial compression occurred at the costoclavicular space in 28 (72%) of the 39 cases and at the interscalene triangle space in 11 (28%) cases. In four patients, the arterial compression was due to a fibrous band (confirmed at surgery in two patients) associated with bone anomalies in three cases. Bandlike structures have already been reported by Panegyres et al (5). The visibility of such abnormal structures represents a fundamental advantage of MR imaging over other imaging techniques and may influence potential surgical treatment. In two patients, arterial compression was due to a cervical rib extending into the costoclavicular space. Interestingly, arterial compression could be observed no matter what form the symptoms took. Nervous compressions were observed in only 7% of the patients.

Our study had the following limitations:

1. The amplitude of the postural maneuvers carried out in our study was limited and was directly influenced by the size of the MR imaging tunnel, as reported by Smedby et al (10). The conventional MR tunnel did not allow an abduction of the arms to a degree inferior to 130°. However, numerous degrees of abduction during clinical evaluation have been reported (11,12,14). One hundred eighteen degrees of abduction has been reported, but we decided not to undertake this maneuver because a false-positive rate of 11% for findings of arterial TOS was described in this study of Doppler US in healthy volunteers (17).

2. The absence of modifications in the interscalene triangle after arm hyperabduction may be related to the fact that the MR imaging examination was performed with patients in a supine position, in contrast to the physical examinations, which were performed with patients in a sitting or standing position. A study of angiography in 115 patients (20) showed that 32% of false-negative results were related to use of the supine position. Rotation of the head during clinical examination has also been reported. We decided not to ask subjects to perform any rotation of the head because the contraction of the scalene muscles achieved by means of head rotation may be uncertain in the supine position. Moreover, physicians do not agree about which way subjects should turn their heads (11).

3. The MR imaging sequences we used did not allow deep inhalation with breath holding because the acquisition times were 4 minutes long. Further studies, including ones involving the use of fast MR imaging sequences that allow the breath to be held while the scalene muscles are contracted, might demonstrate additional dynamic changes.

In conclusion, patients with TOS had a significantly smaller costoclavicular distance after the postural maneuver and a thicker subclavius muscle in both arm positions than did volunteers. Venous compression must be interpreted very carefully because it is observed very frequently in asymptomatic populations. MR imaging was found to be very helpful in demonstrating the location and cause of arterial and nervous compression.

Except for venous thrombosis, vasculonervous compressions were demonstrated only with arm elevation in our study; this fact highlights the value of this postural maneuver in the assessment of patients with TOS.


   FOOTNOTES
 
Abbreviation: TOS = thoracic outlet syndrome

Author contributions: Guarantors of integrity of entire study, A.C., X.D.; study concepts, A.C., X.D.; study design, X.D., C.P.; literature research, C.P., X.D.; clinical studies, B.D., E.H.; data acquisition and analysis/interpretation, C.P., E.B., X.D.; statistical analysis, E.B., X.D.; manuscript preparation and definition of intellectual content, A.C., X.D.; manuscript editing, X.D., E.B.; manuscript revision/review and final version approval, all authors.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 

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