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Presentation (10)-4.pptx imaging in Thoracic outlet syndrome
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- 2. • The thoracicoutlet extends from the cervical spine and superior border of the mediastinum to the lower border of pectoralis minor muscle. • The brachial plexus ,sub clavian vein and subclavian artery traverse the thoracic outlet ,and when compressed ,can result in upper extremity symptoms.
- 3. • TOS isclassified according to which structures are involved. 1.Neurogenic TOS (from compression of brachial plexus nerves) 2.Venous TOS(from compression of subclavian vein) 3.Arterial TOS(from compression of subclavian artery)
- 4. ANATOMY OF THETHORACIC OUTLET/ CERVICOTHORACOBRACHIAL JUNCTION • Anatomically ,the thoracic outlet can be divided into three compartments
- 5. -The inter scalenetriangle Most medial compartment. Bordered by the middle scalene muscle posteriorly,anterior scalene anteriorly and 1st rib inferiorly Contents= subclavian artery and brachial plexus Subclavian vein lies outside the triangle
- 6. - The costoclavicularspace - Bordered by the subclavius muscle anteriorly,clavicle superiorly and the first rib and the middle scalene posteriorly - Contains the entire neurovascular bundle.
- 7. - The Retropectoralisminor space The most lateral compartment The neurovascular bundle course between the pectoralis minor tendon anteriorly and the ribs and intercostal muscles posteriorly
- 8. • The costoclavicularspace is the most frequent site of arterial compression,while the interscalene triangle is the second most frequent site • Neurological compression occurs frequently in both costoclavicular space and in the interscalene triangle
- 9. • TOS isthe constellation of symptoms produced when the neurovascular structures that traverse the thoracic outlet are compressed. • More common in 20-40 years of age • Male:Female =1:4 • The symptoms of TOS are typically reproduced /exacerbated by activity requiring elevation or sustained use of the arms,such as reaching for objects overhead
- 10. CLINICAL FEATURES OFTOS NEUROGENIC TOS(90%) • Symptoms may be sensory or motor • In upper plexus TOS (involving C5,C6,C7 nerves) pain is generally located in the side of the neck and radiates upwards to ear and occipital region • The pain may also radiate posteriorly to the rhomboid area,anteriorly into the upper pectoral region and laterally through the deltoid and trapezius muscle
- 11. • In lowerplexus TOS involving (C8 and T1 nerves) pain is distributed in the anterior or posterior shoulder region and radiates along the inner aspect of the arm. • Parasthesia affects mainly the ring and little fingers with an ulnar nerve distribution. • The end stage of neurogenic TOS is Gilliatt-Sumner hand in which there is atrophy of the hand muscles and hyperesthesia in the ulnar and medial antebrachial cutaneous distributions
- 12. ARTERIAL TOS • Symptomsinclude weaknes,cold and pain in the extremity,caused by ischemic neuritis of the brachial plexus • In case of severe compression,subclavian artery thrombosis with peripheral embolisation can be observed. • Asymptomatic pulsatile mass may be present in the supraclavicular space due to an underlying aneurysm
- 13. VENOUS TOS • Swellingand cyanosis of the extremity with pain and a feeling of heaviness in the upper limb. • Venous distension of the upper arm and shoulder region. • Acute subclavian-axillary vein thrombosis refers to a Paget – Schroetter syndrome. • Pulmonary emboli may be present in patients with occlusive venous TOS
- 14. • TOS shouldremain a diagnosis of exclusion • Differential Diagnosis: - Superior sulcus lung malignancy - Lipomas/Neurogenic tumours in supraclavicular region - Takayasu arteritis
- 15. CONVENTIONAL RADIOGRAPHY • Shouldbe performed in all patients with suspected TOS • Serves as a low cost means of identifying bone anatomic abnormality • The major bone abnormalities that are relevant to TOS and can be detected at plain radiography include: Cervical ribs Elongated C7 transverse process Anomalous first rib Abnormal first rib or clavicle
- 16. CERVICAL RIBS • Thebest way to identify cervical ribs at radiography or CT is to identify the contralateral first rib and confirm that the cervical rib arises from the C7 transverse process. • Complete or Incomplete- Complete cervical ribs(30%) attatch to the normal first rib by fusion or by forming a joint. • Incomplete cervical ribs can be of varying length and usually have a thick ligament extending from their tip to the 1st rib.
- 17. ELONGATED C7 TRANSVERSEPROCESS • An elongated C7 transverse process is defined as extending laterally beyond the transverse process of T1 • Do not demonstrate a costoverteberal articulation while the cervical ribs do
- 18. ANOMALOUS FIRST RIB •Anomalous / Hypoplastic first ribs are the first ribs that articulate with the second rib rather than the sternum. • Tends to lie more cephalad and have more vertical ‘J’ shape • Can cause narrowing at the thoracic outlet due to associated fibrous bands or a bulky articulation with the second rib
- 19. ABNORMAL FIRST RIBOR CLAVICLE • Defined as having either an old fracture or exostosis • Can often heal with bulky callus/heterotopic ossification • Removed with decompression surgery in patients with suspected TOS
- 20. CT ANGIOGRAPHY • SpiralCT is performed first with the arms alongside the body and then with the arms elevated in an attempt to reproduce the neurovascular compression • IV contrast is injected into a vein opposite to that being examined.The scan is started 15-20 seconds after the start of a monophasic injection of 90 mL of iodinated contrast medium at a rate of 4 mL/sec • By comparing the images obtained with the arms along side the body and after elevation ,it is possible to assess the narrowing of various compartments, as well as any dynamic compression of neurovascular structures
- 21. • Arterial compressionis assessed with CT cross sections produced by sagittal reformation of data obtained both in neutral position and after postural maneuvers. • Arterial stenosis has been expressed as the percentage of reduction of the cross sectional area or the diameter of the artery.
- 23. • Venous compressionis very difficult to interpret because such compression is frequently observed in asymptomatic individuals in all the compartments of the tboracic outlet after arm elevation. • Venous thrombosis and collateral circulation are well demonstrated and constitute objective signs of venous TOS
- 24. LIMITATIONS OF CT •Fine analysis of brachial plexus is not possible due to limited CT resolution. • Abduction of the shoulder is limited by the size of the CT tunnel itself ( upper limb elevation > 130 degree is impossible) • CT study is carried out with the patient in supine position,which has an effect on dynamically induced compression • CT is an ionizing radiation and iodinated contrast – medium may be contraindicated or result in adverse effects
- 25. MRI • MRI ofTOS is classically performed by using a phased array coil • Accurate observation of all the anatomic compartments of the thoracic outlet is possible especially with the use of sagittal T1 weighted sequences • The sequences must be performed with the arm in a neutral position and ,also after hyper abduction of the arm
- 28. • Arterial andvenous compressions may be assessed by comparing the arterial cross sectional area at the considered location with arm in a neutral position( along side the body) and after arm elevation. • Arterial compression may also be detected by analysing the arterial calibre along the course of the vessel.
- 30. • MR angiographyis complementary to analysis of arterial cross sectional area on sagittal MR images • This sequence is helpful in detecting post stenotic aneurysmal dialatation. • Preferred IV contrast material is Gadofosveset trisodium single injection at 1 mL/ sec
- 31. • When venousTOS is suspected ,venous thrombosis and collateral circulation must be looked for • If venous thrombosis is found,a brief investigation of the central pulmonary vasculature is done to evaluate for emboli.
- 32. • MRI allowsgood analysis of the brachial plexus due to excellent soft tissue contrast if provides. • The criteria for neurologic compression are disappearance of the fat surrounding the brachial plexus and close contact with the adjacent bony structures.
- 33. • MRI candetect muscle hypertrophy (scalenus,subclavius or pectoralis minor) and abnormal muscles ( scalenus minimus) and fibrous bands • Limitation of MRI is same as that of CT,that is,restriction of arm elevation due to the size of tunnel and the supine position of the patient. • Orientation of anatomic structures may be difficult in very thin individuals due to little adipose tissue.
- 34. ULTRASONOGRAPHY • Power dopplerUSG in association with B mode scanning is used in assesment of subclavian and axillary arterial cross sectional areas. • B – mode scanning can detect anatomic abnormalities such as aneurysmal dialatation and vascular occlusion.
- 35. • Color duplexexamination a/w postural maneuvers (arm in neutral position,90 degree,120 degree,180 degree of abduction) can demonstrate alterations of the blood flow such as complete cessation or increased velocity • The advantage of USG is that it can be performed with the patient in an upright position
- 36. INITIAL MANAGEMENT OFTOS • A conservative approach is the rule in the initial treatment of neurogenic TOS • Relaxing the scalene muscles and strengthening the postural muscles.- physical therapy and hydrotherapy • NSAIDS and muscle relaxants
- 37. • The initialtreatment of arterial TOS is focussed on revascularisation – performed via brachial artery thromboembolectomy. • The initial treatment of effort thrombosis is catheter directed thrombolytic therapy.Maintenence treatment is given with IV heparin ,which is then converted to oral warfarin
- 38. SURGICAL STRATEGIES • Firstrib resection and subclavian artery reconstruction are required when any degree of aneurysmal degeneration is present • Thoracic outlet decompression for venous TOS includes scalenectomy,brachial plexus neurolysis,resection of the 1st rib and circumferential venolysis
- 39. IMAGING OF POSTOPERATIVEPATIENT Immediate postoperative period • The 1st rib will have been resected and drain is typically present in the supraclavicular region. • Many surgeons will intentionally violate the apical pleura to provide a means for decompression of postoperative fluid into the pleural space.Thus small or even moderate pleural effussions or a small pneumothorax may be seen • Associated subcutaneous gas is often seen in the supraclavicular space and chest wall.
- 40. • In manypatients,there will be respiratory splinting on the side of surgery ,consequently, lower lobe atelectasis is a common finding • Elevation of ipsilateral diaphragm due to temporary phrenic nerve dysfunction.
- 41. SHORT TERM COMPLICATIONS(Daysto weeks) • Unexpected vascular damage can result in a supraclavicular hematoma in the post surgical bed • If there is breach of the apical pleural surface and the bleeding is continous ,a hemothorax can result.
- 42. • An enlargingpneumothorax or one that exerts tension typically requires immediate attention • The thoracic duct or right lymphatic duct injury can result in chylothorax. • In CT,chylous effussions manifest as simple fluid with fat –fluid level with in.
- 43. LONG TERM COMPLICATIONS(Months to Years) -APICAL LUNG HERNIATION • Rare potential complication of thoracic outlet decompression. • Occurs due to violation of the apical pleura,allowing the lung to herniate into the supraclavicular space • CT with coronal reconstruction is required to confirm the finding and determine the extent of hernia • Management is wedge resection to treat the hernia
- 44. -REMNANT/ REGROWN FIRSTRIB • Complete resection of first rib involves resection of the sternum anteriorly and the costoverteberal junction posteriorly. • Remnant 1st rib is close to the traversing axillosubclavian vessels and can cause recurrent vascular complications. • CT is the imaging study of choice to detect remnant 1st rib.
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