P095: THE BRACHIAL PLEXUS: UNCHARTED TERRITORIES
Patricia Narciso, DO1; George Barsoum, MD1; Steven Porter, MD1; Christopher B Robards, MD1; Bradley S Schoch, MD1; Hillary W Garner, MD1; Michael J Franco, MD2; 1Mayo Clinic Florida; 2Cooper University Hospital
Introduction: Knowledge of brachial plexus anatomy is essential when performing regional anesthesia for the upper extremity. Anomalous brachial plexus anatomy has been reported in 13%-35% of cases1-3. Two reported variants include anomalous course of the roots anterior or within the scalene musculature and abnormal separation of the cords around the subclavian artery4,5. These anomalies were detected with ultrasonography, which has proven to be a valuable tool for delineating anatomy and providing imaging guidance during regional anesthesia. We report a previously undescribed course of the brachial plexus relative to the subclavian artery within the supraclavicular fossa that was identified by ultrasound (US) prior to regional anesthesia.
Case Presentation: A 71-year old male presented for right-sided revision rotator cuff repair. The plan for post-operative pain control included the pre-operative placement of an interscalene brachial plexus nerve catheter for continuous infusion. During routine evaluation of the right supraclavicular fossa using US guidance, an anomalous course of the brachial plexus was discovered. Instead of the usual position of the brachial plexus divisions located lateral to the subclavian artery, the divisions were found coursing in a cluster medial to the subclavian artery (image 1). Videography of the region better demonstrated the orientation of the brachial plexus as the roots of the brachial plexus coalesce to become divisions around the subclavian artery. Following recognition of this anomaly, the plexus was tracked more distally along the axillary artery in the infraclavicular space. In this location, the usual orientation of the cord is medial, lateral, and posterior to the axillary artery – positions by which these individual cords are named. In our patient, however, all three cords were positioned superficial to the axillary artery (Image 2). Examination of the contralateral non-operative extremity with US revealed the expected orientation and course of the brachial plexus (brachial plexus divisions lateral to the supraclavicular artery). Of note, the patient denied any history of trauma to his operative arm, shoulder, or neck. We decided to place a brachial plexus catheter using a more proximal interscalene approach where his anatomy appeared conventional. The block provided adequate anesthesia post-operatively and the patient’s postoperative inpatient and outpatient course was uneventful.
Discussion: US guidance has become part of the standard of care for administering regional blocks. Research in regional anesthesia has shown the particular value of US guidance in cases of anatomic variants. Our case provides additional evidence of the wide variations in brachial plexus anatomy, even within the same individual. Although the value of US is well-established, highlighting the benefits of real-time dynamic US for planning and delivering regional anesthesia in unique situations is paramount to continually advancing the safety and efficacy of this important clinical tool.
Image 1: US-image of brachial plexus divisions (green) medial to subclavian artery. Yellow = first rib, ScA = subclavian artery
Image 2: US-image of brachial plexus cords (green) superficial to the axillary artery. AA = axillary artery, AV = axillary vein, PecMi = pectoralis minor muscle