The Axillary Region in a High Resolution MRI

Overview

The axillary region is regularly used for brachial plexus block. The technique may be guided by nerve stimulation, ultrasound or a combination of nerve stimulation and ultrasound. Magnetic resonance imaging (MRI) has been beneficial in presenting anatomy of interest for regional anesthesia and in demonstrating spread of local anesthetic (LA). An axillary MRI-study at our department supported the suggestion of multiple rather than a single injection technique. Using a 0.5 Tesla open MR scanner in that study, the investigators were not able to distinguish terminal nerves from equally sized vessels. Therefore the investigators could not definitely answer whether the LA reached the pertinent nerves. The investigators have recently performed an axillary block study with a 3.0 Tesla scanner. Now the terminal nerves were identified and for each patient the investigators could observe if the LA reached the nerves. The aim of this study was to demonstrate the anatomy of the brachial plexus in the axillary region at different levels. The investigators present the best pictures of the nerves with and without LA injected. The images are demonstrated in the axial and coronal plane.

For upper limb surgery, the brachial plexus can be blocked at the interscalene, supraclavicular, infraclavicular and axillary level as an alternative to general anesthesia. The axillary block requires more deposits to achieve a complete block. MRI investigations are of interest to better understand the block specific distribution of LA. With the new MRI Achieva 3.0T X-series (Philips Electronics, Eindhoven the Netherlands), with resolutions beyond 100μm using 2k imaging, we expected new information also compared with the earlier axillary MRI publication from our department. In that former study we used a single deposit technique in an open 0.5 Tesla scanner. We could not in that study recognize the terminal nerves or determine if the LA reached the axillary plexus. MRI publications of the brachial plexus mostly study the shoulder region and few are describing the axillary region. We did not find any article describing the axillary brachial plexus using a 3.0 Tesla high resolution MRI. Ultrasound visualizes the plexus nerves in the axilla and demonstrates dynamically the spread of LA. This usually occurs in 2-dimensional images where the initially observed LA fades after some minutes. MRI provides more easy 3 - dimensional images also in oblique planes compared with ultrasound. This study was done in order to demonstrate the relevant anatomy in the volunteers and the spread of LA in patients. We also present the used protocols and MRI - stacks after having optimized the configuration of the 3.0 MRI scanner.