Supraclavicular Block Anatomy — FRCA Primary MCQ

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ModerateAnatomySupraclavicular Block AnatomyFRCA Primary

In the usual ultrasound view for a supraclavicular brachial plexus block, a compact cluster of neural elements lies lateral and posterior to the subclavian artery and overlies the first rib. Which components of the brachial plexus form this cluster?

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Correct answer: B — The trunks approaching their divisions

Explanation lettering: E = shown as A · A = shown as B · B = shown as C · C = shown as E

A is correct. At the supraclavicular level, the three trunks remain closely bundled as they approach and begin to form their anterior and posterior divisions. On ultrasound this compact neural cluster lies lateral and posterior to the subclavian artery, over the first rib and near the pleura. This arrangement permits a dense upper-limb block from a relatively localised injection. The ventral rami pass through the interscalene groove more proximally, making D an interscalene rather than supraclavicular description. The cords are found infraclavicularly in relation to the axillary artery, excluding C. At the intervertebral foramina and in the proximal arm, the neural elements are respectively too proximal or have separated into individual terminal nerves.

Reference: Neal JM et al. Upper extremity regional anesthesia: essentials of our current understanding. Regional Anesthesia and Pain Medicine. 2009;34:134–170. https://pubmed.ncbi.nlm.nih.gov/19282714/