MRI is used to evaluate the presence of thoracic outlet syndrome causing brachial plexopathy. Three spaces are evaluated: the interscalene triangle, costoclavicular space, retropectoralis minor space. The costoclavicular space is the most commonly compressed, followed by the interscalene triangle. MRI or MRA imaging with the affected arm in a normal followed by hyperabducted position to make the spaces more arrow demonstrates narrow subclavian artery or brachial plexus impingement.  Focal abnormal brachial plexus T2-weighted hyperintensity with or without distortion; as well as scalene muscle inflammation or fibrosis may be present ¹.

Various lesions can be the cause of thoracic outlet syndrome and are visible on MRI ^1,2:

• Bony – cervical rib, long transverse process of C7 vertebrae, callus, osteochondroma of clavicle or first rib, bilateral hypoplastic first ribs fused second ribs
• Soft tissue – fibrous band, hypertrophy of scalenus anterior, hypertrophy of scalenus minimus, fibrous scarring 
  • MRI can show fibrous band and asymmetry from elongated transverse process of C7 or cervical rib to first rib, leading to compression of C8 or T1 roots or inferior trunk

Case courtesy of A/Prof Pramit Phal.