Usefulness of high-resolution ultrasound for small nerve blocks: Visualization of intercostobrachial and medial brachial cutaneous nerves in the axillary area

Abstract

Introduction High-resolution ultrasound (HRU) allows one to identify small nerves, but in the clinical setting, intercostobrachial nerve (ICBN) and medial brachial cutaneous nerve (MBCN) are not identified with conventional portable ultrasound (CPU) devices. The aim of this study is to identify both nerves and describe their relation with specific anatomical structures which could be easily identified with the ultrasound devices available in the clinical setting. Methods 21 healthy patients were scanned using HRU bilaterally in the axillary area located over the conjoint tendon to find the ICBN and MBCN and describe their anatomic relations. 5 fresh cadavers were used to validate the previous anatomical findings. ICBN and MBCN ultrasound-guided block was performed with 5 mL of methylene blue and iodine contrast, and the distribution was assessed by both CT scan and dissection. Results ICBN and MBCN were identified in all cases. The average distance of the ICBN branches to the artery was 35±6 mm in men and 27±5 mm in women. Constant identification of the muscle-tendon junction of the latissimus dorsi muscle with respect to the location of the branches of the ICBN nerve was observed. Dissection and CT scan confirmed these findings. Conclusion HRU is a useful tool to identify ICBN and MBCN nerves, and to describe structures which can be easily identified with CPU use in the clinical setting.