Thoracic outlet syndrome Aims and objectives – To demonstrate the role of 4D dynamic MRA( TWIST MRA) in thoracic outlet syndrome
3D CE MRA Vs 4D Dynamic ( TWIST ) MRA CE 3D MRA provides high resolution 3D MRA data set of the vascular target region. The images are static and does not provide dynamic flow information 4D Dynamic ( Twist ) MRA (Time resolved angiography with stochastic tragectories ) with high temporal resolution offers 3D data set of images along with dynamic flow information.
Techniques of twist- 4D TWIST MRA done after injecting 5-7 cc of contrast followed by application of MRA sequences immediately after the contrast administration with multiple measurments are taken in rapid succession. Contrast timing is less critical Images are evaluate in MIP format in cine mode to visualized real time flow TWIST MRA has advantage of answering vascular diagnostic questions where blood flow dynamics play a role such as atareovenous malformations, venous malformation in the brain. For the reasons indicated above TWIST MRA is gaining clinical importance. This novel 4d MRA can be used in studying thoracic outlet syndrome where documentation of subclavian artery compression on arm elevation is must in diagnosing vascular thoracic outlet syndrome
4D DYNAMIC MRA Twist MRA 8 measurements Fov – 450 Body matrix coil -- 12 channel Contrast – 7 cc, IV, hand injection Total scan time – 4 minutes
CASE 1 Female 31 yrs presented with pain on arm elevation with clinical assessment suggestive of arterial thoracic outlet syndrome Twist MRA done by injecting 5 – 8 cc of gadolinium contrast via the opposite upper limb It has demonstrated focal severe stenosis of left subclavian artery on arm elevation and normal flow in arm neutral position
4D DYNAMIC MRA – ARM NEUTRAL POSITION (click on the image)
4D DYNAMIC MRA – ARM ELEVATED POSITION( click on the image)
THORACIC OUTLET Three compartments Interscalene triangle Costo clavicular space Retopectoralis minor space Dynamically induced compression of neural,arterial,venous structures --- thoracic outlet syndrome Age- 20-40 yrs Female – male ratio- 4:1 Symptoms – elevation of arms Three distinct syndromes – Neurogenic ( 90-95%), arterial (5-10%),venous Provacative clinical tests – Roos test, Adsons test, Wright test, costoclavicular test
THORACIC OUTLET There are three common sites of compression: scalene triangle- between scalenus anterior and scalenus medius muscles costoclavicular space between clavicle and 1 st rib Subpectoral space - between pectoralis minor and coracoid process The scalene triangle is defined by the first rib and the anterior and middle scalene muscles and is the most medial compartment. The subclavian artery and branches of the brachial plexus pass through the borders of this triangle while the subclavian vein passes anterior to it.
THORACIC OUTLETE SYNDROME- Thoracic outlet syndrome (TOS) refers to a group of clinical syndromes caused by congenital or acquired compression of brachial plexus (neurogenic TOS) or subclavian artery or subclavian vein as they pass through the thoracic inlet. NEUROGENIC TOS Sensory/Motor Upper plexus TOS– C5,C6,C7 nerves Lower plexus TOS- common,C8,T1 nerves ARTERIAL TOS Weakness, cold and pain Complication – sub clavian artery thrombosis with peripheral embolization
Venous TOS-Pain,swelling, cyanosis – subclavian vein compression leads to swelling and thrombosis- paget schroetter syndrome TOS - Etiologies Scalenus anticus syndrome- Bone abnormalities – cervical rib Elongated C7 transverse process First Rib /clavicle (Tumor/Exostosis, excessive callus) Soft tissue abnormalities Poor posture and weak muscular support in thin woman Cervical rib Increased incidence in TOS ( 5-9% in TOS,1% In normal population) COMLETE-INCOMPLETE Clue to tight fibrous band - Elevation of sub clavian artery
CONGENITAL SOFT TISSUE ABNORMALITIES Anterior scalene muscle hypertrophy Common belly origin of scalene muscles Brachial plexus passing through anterior scalene muscle Broad middle scalene Interdigitations between scalene muscles Supernumery muscles – scalene minimus muscle Anomalous fibrous bands IMAGING MODALITIES- PLAIN RADIOGRAPHY – cervical spine and CXR CT ANGIOGRAPHY MRI WITH MRA DOPPLER
Ct angiography Useful to asses vessels and bony relations Fine analysis of brachial plexus not possible
Other applications Other conditions TWIST MRA used are Limb vascular malformation- venous hemangioma,AVM Peripheral Arterial disease Hand vascularity - small vessel disease of the hand