Interscalene Block Anatomy — FRCA Primary MCQ

Instant feedback + full explanation. One question, done properly.

EasyAnatomyInterscalene Block AnatomyFRCA Primary

During an ultrasound-guided interscalene brachial plexus block at the level of the cricoid cartilage, between which two muscles are the C5–C7 nerve roots typically identified?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Anterior scalene and middle scalene

Option E is correct. At the standard interscalene ultrasound level near the cricoid cartilage, the C5–C7 roots are identified in the interscalene groove between the anterior scalene and middle scalene muscles. These roots unite more distally to form the brachial plexus trunks, so specifying the roots is anatomically more precise for this view. The interval between the middle and posterior scalenes is too posterior. Sternocleidomastoid is superficial to the region but does not bound the interscalene groove. Subclavius, pectoralis minor and the intercostal muscles are infraclavicular or thoracic structures and are not boundaries of the interscalene space.

Reference: RCoA-hosted Plan A Blocks, Upper Limb & Trunk: Interscalene Brachial Plexus Block, 2020. https://www.rcoa.ac.uk/sites/default/files/documents/2020-11/Plan%20A%20-%20Upper%20%20Lower%20Limb_A0_FINAL_With%20crop%20marks.pdf