High-resolution MRI demonstrates detailed anatomy of the axillary brachial plexus. A pilot study.

Axillary block is the most commonly performed brachial plexus block and may be guided by nerve stimulation or ultrasound. Magnetic resonance imaging (MRI) has proven to be beneficial in presenting anatomy of interest for regional anaesthesia and in demonstrating spread of local anaesthetic. The aim of this pilot study was to demonstrate the anatomy as shown by MRI of the brachial plexus in the axillary region. Nine volunteers and nine patients were examined in a 3.0 Tesla MR. The patients had two different brachial plexus blocks. Subsequently, they were scanned by MRI and finally tested clinically for block efficacy before operation. Axial images, with and without local anaesthetics injected, were viewed in a sequence loop to identify the anatomy. With the high-resolution MRI, we obtained images of good quality, and cords and all terminal nerves could be identified. When local anaesthetics are injected, neurovascular structures are displaced, and the vein is compressed. Viewing the images in a sequence loop facilitates identification of the different nerves and has high instructive value (links S1-3 to these loops are enclosed). Clinical high-field 3.0 Tesla MRI scanner gives good visualization of brachial plexus in the axilla. The superior ability to detect local anaesthetics after it has been injected and the multiplanar imaging capability make MRI a useful tool in studies of the brachial plexus.