THORACIC OUTLET SYNDROME

Alexandru AndritoiuMilitary Hospital Craiova, Romania

Diagram shows the three compartments of the Diagram shows the three compartments of the thoracic outlet and their componentsthoracic outlet and their components

Demondion X et al. Radiographics 2006;26:1735-1750

Diagram shows the three compartments of the thoracic outlet and their components. AS = anterior scalene muscle, BP = brachial plexus, C = clavicle, CC = costoclavicular space,IT = interscalene triangle, MS = middle and posterior scalene muscles, Pmi = pectoralis minor muscle, RP = retropectoralis minor space, SA = subclavian artery, SM = subclavius muscle, SV = subclavian vein.

Definition

• Thoracic outlet syndromes are caused by compression of the neurovascular structures passing through the thoracic outlet.

Anatomic sections show the compartments of the thoracic outlet

Demondion X et al. Radiographics 2006;26:1735-1750

Fig.  Anatomic sections show the compartments of the thoracic outlet. (a) Section obtained after removal of the pectoralis major muscle shows the costoclavicular space (red oval) and retropectoralis minor space (yellow oval). Pmi = pectoralis minor muscle.

Anatomic sections show the compartments of the Anatomic sections show the compartments of the thoracic outletthoracic outlet

Demondion X et al. Radiographics 2006;26:1735-1750

Fig. (b) Section obtained after removal of the pectoralis minor muscle shows the neurovascular bundle. C = clavicle, straight black arrow = axillary artery, curved black arrow = axillary vein, white arrow = brachial plexus.

Classification• Subgroup 1Subgroup 1 - - ((neurologic typeneurologic type)) – 95% of cases This type is secondary to compression of the brachial plexus

caused by various soft tissue and bony abnormalities at the point where the nerves pass between the anterior and middle scalene muscles.

• Subgroup 2 - (the venous type): 3-4% of cases. Venous thrombosis may be categorized into primary and secondary

thrombosis based on the etiology. Primary venous thoracic outlet syndrome, or primary venous thrombosis, is also called Paget-Schrötter syndrome. The disease is named after the 2 individuals who first described this entity: Paget, who described it in 1875, and von Schrötter, in 1884. Other terms for this condition include effort thrombosis, spontaneous thrombosis, and traumatic thrombosis.

• Subgroup 3Subgroup 3 ( (the arterial type): 1-2% of cases. This type is associated with the most serious complications,

including limb ischemia (which may result in the loss of the affected upper extremity).

• Race No racial predilection exists.• Sex Thoracic outlet syndrome is traditionally

more common in women than in men, with a female-to-male ratio as high as 3:1.[6 ]

• Age Thoracic outlet syndrome is most common

in people aged 10-50 years

DIAGNOSIS• Clinical maneuversClinical maneuvers• RadiographyRadiography• UltrasonographyUltrasonography is readily available and relatively

inexpensive, and it can be performed in both arterial and venous thoracic outlet syndrome.

• Magnetic resonance (MR) angiographyMagnetic resonance (MR) angiography and computed tomographic (CT) angiography(CT) angiography of the thoracic inlet, especially with recently devised techniques and protocols, are promising noninvasive modalities that may soon provide image quality comparable to that of angiography and venography.

• Angiography and venographyAngiography and venography remain the criterion standards for the radiologic diagnosis of these conditions, and they have the added benefit of enabling potential endovascular treatment.

Thoracic outlet maneuvers

• may be performed during an imaging examination if spectral analysis is performed at the radial or ulnar artery before and during the following maneuvers:

Adson maneuver

• Evaluates compression by the scalenus anticus muscle or cervical rib.

• The patient takes a deep breath, extends the neck back and upward and then turns the head first to the right and then to the left.

TThhe Roos teste Roos test

• The patient repeatedly clenches and unclenches the fists while keeping the arms abducted and externally rotated (palms forward and upward). The elbows are braced slightly behind the frontal plane.

• The test is positive when symptoms are reproduced with this maneuver.

• A positive test is very suggestive of the thoracic outlet syndrome.

Hyperabduction maneuver

• Evaluates compression of the neurovascular bundle between the coracoid process and the pectoralis minor muscle.

• The patient externally rotates the shoulders and extends the arms out from the chest and then above the head.

Costoclavicular maneuver

• Evaluates compression of the neurovascular bundle between the clavicle and the first rib.

• The patient assumes an exaggerated military position with shoulders pushed backward and pressed downward.

Principal Causes of TOS

Arterial compression in a 37-year-old man.Arterial compression in a 37-year-old man.

Demondion X et al. Radiographics 2006;26:1735-1750

Ultrasonography

• Continuous-wave Doppler ultrasonography (US) has the advantage of enabling assessment of blood flow during performance of the clinical tests used in clinical practice.

• This technique is frequently used to confirm the clinical suspicion of arterial TOS. However, it is based on indirect signs of more proximal arterial stenosis and does not demonstrate the exact site of the arterial compression.

• The usefulness of power Doppler US in association with B-mode scanning has recently been reported in the assessment of subclavian and axillary arterial cross-sectional areas in patients with clinical suspicion of arterial TOS.

• B-mode scanning may allow detection of anatomic abnormalities such as aneurysmal dilatation and deviation of vessels.

• Color duplex sonographic examination associated with postural maneuvers (arm in neutral position, 90°, 120°, and 180° of abduction) may demonstrate alterations of the blood flow, such as complete cessation of blood flow or increase of blood flow velocity (,,).

AAdvantagedvantages of USs of US• the direct comparison between dynamically induced symptoms and

concomitant visualization of the vessels. • the possibility of performing the examination with the patient in an

upright or seated position, as in clinical examination, in contrast to CT and MR imaging, which are performed with the patient in a supine position.

• Unfortunately, this technique does not allow an accurate overview of the thoracic outlet region nor in particular an analysis of the region of the pulmonary apex. It must always be kept in mind that thoracic outlet symptoms may reveal locoregional disease such as a superior sulcus lung tumor (Pancoast-Tobias). For this reason, sonography should not be used solely to assess TOS; rather, it appears to be a valuable supplementary technique to CT or MR imaging in the event of clinical discordance, especially in patients with positive clinical features of TOS but negative features of TOS at CT and MR imaging.

•

The criteria for hemodynamically significant compression

Venous compresionVenous compresion:• the obliteration of flow through the subclavian vein or the

loss of normal cardiac pulsatility or respiratory phasicity.AArterial narrowingrterial narrowing• a 2-fold or greater increase in the peak systolic velocity

compared with that measured with the arm in the neutral position or the obliteration of flow.

A venogram of a 20-year-old woman with right arm swelling that shows occlusion of the right subclavian vein as it passes through the thoracic inlet. A wire was advanced across the occlusion into the superior vena cava.

Thoracic outlet syndrome (venous subtype)Thoracic outlet syndrome (venous subtype)

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Fig.  Thoracic outlet syndrome (venous subtype). (a) Coronal MIP images from a contrast-enhanced MR angiographic study performed with arms up positioning demonstrate normal-caliber patent subclavian arteries bilaterally in the arterial phase image on the left and stenosis of the distal right subclavian vein (arrow) in the venous phase image on the right. (b) Axial MIP image from contrast-enhanced MR angiographic study performed with arms up positioning again demonstrate a severe distal right subclavian vein stenosis (arrow). (c) Coronal MIP image from the same study performed with patient’s arms in neutral position shows that the right subclavian vein has returned to normal caliber (arrow), demonstrating the dynamic changes at the thoracic outlet that can elicit clinical symptoms and different imaging findings.

Follow-up careFollow-up care

Duplex ultrasonography has been useful in the follow-up care of patients after surgical or radiologic intervention, and a baseline postprocedural examination is routinely performed.

Longley B et al. Color Doppler ultrasound of thoracic outlet syndrome. Semin Intervent Radiol. 1990;7:230-5.