Cadaveric study identifying clinical sonoanatomy for proximal and distal approaches of ultrasound-guided intercostobrachial nerve block

Background and objectives The intercostobrachial nerve (ICBN) has significant anatomical variation. Localization of the ICBN requires an operator's skill. This cadaveric study aims to describe two simple ultrasound-guided plane blocks of the ICBN when it emerges at the chest wall (proximal approach) and passes through the axillary fossa (distal approach). Methods The anatomical relation of the ICBN and adjacent structures was investigated in six fresh cadavers. Thereafter, we described two potential techniques of the ICBN block. The proximal approach was an injection medial to the medial border of the serratus anterior muscle at the inferior border of the second rib. The distal approach was an injection on the surface of the latissimus dorsi muscle at 3-4 cm caudal to the axillary artery. The ultrasound-guided proximal and distal ICBN blocks were performed in seven hemithoraxes and axillary fossae. We recorded dye staining on the ICBN, its branches and clinically correlated structures. Results All ICBNs originated from the second intercostal nerve and 34.6% received a contribution from the first or third intercostal nerve. All ICBNs gave off axillary branches in the axillary fossa and ran towards the posteromedial aspect of the arm. Following the proximal ICBN block, dye stained on 90% of all ICBN's origins. After the distal ICBN block, all terminal branches and 43% of the axillary branches of the ICBN were stained. Conclusions The proximal and distal ICBN blocks, using easily recognized sonoanatomical landmarks, provided consistent dye spread to the ICBN. We encourage further validation of these two techniques in clinical studies.