Anatomical variation of the brachial plexus roots identified during pre-procedural ultrasound for an interscalene block

Dear Editor, In shoulder surgery, the interscalene brachial plexus block (ISB) remains the most frequently employed technique. At this level, the brachial plexus roots are known to display several anatomical variations. In this letter, we report an anatomical variant of the brachial plexus roots observed during an ultrasound scan prior to performing an ISB. We illustrate the observed sono-anatomy features of the variant seen, offer an explanation as to why targeting this variant may clinically result in a failed block, and describe a rescue strategy. [...]