Don't be perplexed by the plexus! A practical approach to brachial plexus ultrasound

Figures

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  Figure 1.. Scan position for the (A) supraclavicular brachial plexus, (B) subcoracoid area, and (C) axillary fossa.

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  Figure 2.. (A) The C7 transverse process has a large posterior tubercle (arrow) (“thumbs up sign”) with no anterior tubercle. The C7 root lies anterior to the posterior tubercle. (B) The C6 vertebral body has equal-sized anterior and posterior tubercles. The C6 nerve root lies between the C6 tubercles.

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  Figure 3.. (A) Transverse ultrasound of the interscalene gap shows the monofascicular upper (U), middle (M), and lower (L) trunks of the brachial plexus. The classic “traffic light sign” is not always seen. The phrenic nerve is shown (open arrow). (B) Transverse ultrasound of the interscalene gap shows the dorsal scapular artery (arrowhead) passing through the middle and upper trunks of the brachial plexus. The suprascapular nerve is shown (block arrow). Abbreviations: Sa = scalenus anterior muscle; Sm = scalenus medius muscle.

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  Figure 4.. (A) Transverse ultrasound of the posterior triangle showing the “bunch of grapes” appearance of the divisions (arrows) aligned superomedial to the subclavian artery (ScA). (B) Transverse colour Doppler ultrasound shows the transverse cervical artery passing over the divisions of the brachial plexus.

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  Figure 5.. Schematic diagram of costoclavicular gap. Abbreviations: SC = subclavius muscle; SA = scalenus anterior; SM = scalenus medius; A = subclavian artery; V = subclavian vein.

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  Figure 6.. (A) Schematic diagram of infraclavicular area. (B) Transverse ultrasound examination showing the cords (arrows) aligned alongside the axillary artery (AxA). Abbreviations: Pmi = pectoralis minor; Pmj = pectoralis major; AxV = axillary vein.

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  Figure 7.. Transverse ultrasound of axillary fossa showing the musculocutaneous nerve (MCN) lying between the biceps (B) and coracobrachialis (Cb) muscles. The median nerve (M) consistently lies closest to the biceps muscle. The radial nerve (R) tends to lie towards the posterior of the axillary artery while the ulnar nerve lies superomedial to the axillary artery between the radial and medial nerves.

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  Figure 8.. Longitudinal ultrasound showing a medium-sized nerve sheath tumour arising from the C5 root of the brachial plexus, which is in continuity with the tumour. The tumour (thick arrow) shows severe cystic degeneration with moderate posterior enhancement (open arrow).

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  Figure 9.. (A) Transverse ultrasound showing severe irradiation plexopathy of the interscalene triangle with perineural fat fibrosis leading to poor definition of the trunks (arrows) as well as severe dermal and subcutaneous thickening and hypoechogenicity due to fibrosis. (B) Transverse ultrasound showing moderate to severe irradiation plexopathy of the divisions, which are thickened, ill-defined, and clumped with hypoechogenicity of the adjacent fat due to fibrosis (arrows). Abbreviations: Sa = scalenus anterior muscle; Sm = scalenus medius muscle.

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  Figure 10.. 27-year-old man with arm weakness following traction injury. (A) T2-weighted fat-suppressed MR image shows severe oedema in the subcoracoid and axillary regions (open arrows) but no specific nerve injury. (B) Longitudinal ultrasound, on the following day, shows severe musculocutaneous nerve swelling (arrows) consistent with a severe traction injury.

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  Figure 11.. 68-year-old man with known diffuse large B-cell lymphoma and arm pain for 2 months. Transverse US shows severe thickening of the soft tissues around the divisions (arrows) lateral to the subclavian artery (ScA) consistent with lymphoma infiltration. The suprascapular nerve deep to the omohyoid muscle (Omh) is not involved (arrowhead).

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  Figure 12.. Schematic diagram showing indentation of lower trunk (L) (“wedge-sickle sign”), which can be caused by a fibromuscular band, a prominent or medially placed scalenus medius muscle, or a high-riding first rib (arrow). Abbreviations: Sa = scalenus anterior muscle; Sm = scalenus medius muscle; ScA = subclavian artery.