Imaging of Thoracic Outlet Syndrome Constantine A. Raptis, MD

Imaging of the patient with Thoracic Outlet Syndrome

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Constantine A. Raptis, MD Director of Thoracic MRI Mallinckrodt Institute of Radiology St. Louis, MO

Goals of this presentation

No disclosures

• Review the imaging modalities used in the evaluation of the patient with suspected thoracic outlet syndrome • Present imaging findings associated with the diagnosis of thoracic outlet syndrome • Discuss Di common postoperative t ti complications of corrective surgery

What is the thoracic outlet?

What is Thoracic Outlet Syndrome?

• Extends from the cervical spine and mediastinum to the lower border of the pectoralis minor muscle • 3 compartments: – Interscalene I t l ti triangle l – Costoclavicular space – Retropectoralis R li minor i space

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Please note that for this version for the syllabus, I have omitted the cases/images that will be included in the presentation.

• Compression of the neurovascular structures that traverse the thoracic outlet • More common in patients less than 40 years old • F:M F M approximately i t l 4:1 41

It’s It s really three diseases • • • •

Neurogenic syndrome Arterial syndrome V Venous syndrome d Typically, neurogenic syndrome thought to account for over 90% of cases, but this may be an overestimate and be due to recruitment bias

Symptoms • Neurogenic: Pain and paresthesia – Neck, ear, occipital region, upper back, clavicle, chest,, arm -> depends p on where compression p is

• Arterial: Weakness, cold, pain, embolic p phenomena • Venous: Swelling and cyanosis, venous distension • Provocative maneuvers are important in the physical exam

Role of imaging prior to surgery

– Some centers more likely to manage neurogenic thoracic outlet syndrome conservatively

• Evaluate for other etiologies for the patients symptoms

Conventional Radiographs • Cervical rib – Less than 1% of the population, but seen in 55-10% of patients with TOS – Arises from C7 – Can be complete or incomplete – Often associated with a fibrous band

• Plain radiographs – Excellent for initial survey of bony abnormalities

• Ultrasound – Can be used to look for thrombus,, dilated collaterals,, positional changes

• CT – Excellent for bony abnormalities, but has radiation concerns in typically young population

• MRI – Modality of choice for evaluation of vascular TOS

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• Important to detect anatomic abnormalities • Helpful in discriminating neurogenic from vascular thoracic outlet syndrome

Choice of modalities

• Angiography – Choice for the acutely symptomatic patient as it provides a means of treatment

Conventional Radiographs • Elongated transverse process of C7 – Considered elongated if tip extends below transverse process of T1 below – Can C also l b be associated with fibrous band

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Conventional Radiographs • Anomalous first rib – Fuses to second rib rather than sternum

• Abnormal first ribs or clavicle – Old fractures – Exostoses

Ultrasound • Can assess blood flow during clinical maneuvers • Frequently relies on indirect signs of more proximal arterial stenosis • Difficult to image exact level of stenosis • Can be performed with patient upright • At our institution institution, ultrasound for TOS typically only done in office and as an adjunct to CT or MRI

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Angiography • Typically reserved for the patient presenting with acute symptoms suspicious for venous TOS • Venogram performed with arms at varying degrees of abduction • If thrombus is detected, a declot can be performed f d

Computed Tomography • Technique – IV on asymptomatic side – Split bolus (5 minutes between injections) • 4 cc/sec injectino

– First run: Arm of interest up, head towards ipsilateral side • Time off aorta • Then venous phase at 90 seconds

– Second run: Arm of interest down • Time off aorta • Then venous phase at 90 seconds

Magnetic Resonance Imaging • Technique – Phased array coil – IV on asymptomatic y p side – Contrast agent choice • Intravascular agent (1 cc/sec) – Allows for single injection – Will have venous opacification on all runs after initial arterial phase

• Extracellular agent (2 cc/sec) – Can get pure arterial phase with arms up and arms down – Requires q two injections j

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Magnetic Resonance Imaging • Protocol ((for intravascular agent) g ) • Arms at side – – – –

TSE T1 Hi Hi--res coronal TSE T1 HiHi-res axial Test bolus timed for arch 3D VIBE axial breath hold centered at arch (pre contrast) – 3D MRA coronal breath hold (pre contrast) – Give contrast – 3D MRA coronal breath hold (post contrast x 3) • Run 1 timed for aorta, Run 2 after 12 seconds, then Run 3 after 40 seconds

– 3D VIBE axial i l breath b th hold h ld (post ( t contrast) t t)

MRI Technique Continued • Arms above head head, head to symptomatic side – 3D MRA coronal breath hold x2 – 3D VIBE axial breath hold – No need to rebolus patient when using an intravascular agent

MRI for brachial plexus • Not routinely performed at our institution institution, focus is on vascular etiologies • Can evaluate brachial plexus by adding supplemental T1 Hi Hi--res sagittal images with arms up and arms down

• Post processing – Obtain subtractions and MIPs as needed

Findings g on cross sectional imaging g g

Imaging the post post--operative patient

• Arterial TOS Arterial compression p with arms elevated PostPost-stenotic dilatation Aneurysm or pseudoaneurysm formation Collaterals Fibrous bands Thrombus (rare)

• Venous TOS – Venous V compression i with ith arms elevated l t d • Significance of venous compression can be difficult to determine given preponderance of even moderate venous narrowing with positional changes in normal individuals

– Thrombus Th b – Fibrous bands – Enlarged collateral vessels

• Neurogenic TOS

• Manyy surgical g techniques q available for thoracic outlet syndrome decompression – Different approaches – Most M t resectt th the entirety ti t off the th fifirstt rib ib and d cervical i l ribs ib – Resection of muscles about the thoracic inlet is variable – Vascular reconstruction or stenting may be necessary

• Many surgeons intentionally violate the apical pleura to provide a means of decompression of postoperative fluid/hematoma into the pleural space

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– – – – – –

– Loss of fat surrounding brachial plexus with arms elevated

Imaging the post post--operative patient • Expected findings on postoperative chest radiographs – Small or moderate pleural fluid collections – Small pneumothorax – Extrapleural hematoma at apex

Imaging the post post--operative patient • Potential complications – Hemothorax – Chylothorax y – Pneumothorax – Supraclavicular p infection or hematoma – Pulmonary infection – Lung herniation – Nerve damage – Vascular injury/ injury/rethrombosis rethrombosis

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Patients presenting with symptoms after f previous i d decompression i

Delayed presentation

• Imaging may be necessary to see exactly what procedure was performed • Often important to assess the amount of remnant first rib

• Grafts and stents prone to restenosis

– This Thi iis best b t done d with ith CT – Complete resection involves resection of entire first rib posteriorly to the costovertebral junction and anteriorly to junction with sternum

• Imaging the contralateral side is often important as bilateral TOS is not uncommon

Conclusion

– Can evaluate with CT or MRI – Many of these patients go straight to angiography for attempted declot

References/Suggested Reading •

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• Imaging g g of p patients with thoracic outlet syndrome y plays an important role in diagnosis and postoperative care • CT and d MRI remain i the th key k imaging i i modalities d liti for f evaluating thoracic outlet syndrome patients, with CT p preferred for investigating g g bony y abnormalities and MR preferred for vascular and soft tissue abnormalities • Knowledge of expected imaging findings in TOS patients is essential for accurate diagnosis

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