Anatomic Variation of the Phrenic Nerve and Brachial Plexus Encountered during 100 Supraclavicular Decompressions for Neurogenic Thoracic Outlet Syndrome with Associated Postoperative Neurologic Complications

Background: The objective of this study was to characterize phrenic nerve and brachial plexus variation encountered during supraclavicular decompression for neurogenic thoracic outlet syndrome and to identify associated postoperative neurologic complications. Methods: A multicenter retrospective review was performed to evaluate anatomic variation of the phrenic nerve and brachial plexus from November 2010 to July 2018. After initial characterization, the following two groups were identified: variant anatomy (VA) group and standard anatomy (SA) group. Complications were analyzed and compared between the two groups. Results: In total, 105 patients were identified, and 100 patients met inclusion criteria. Any anatomic variation of the standard course or configuration of the phrenic nerve and/or brachial plexus was encountered in 47 (47%) patients. Phrenic nerve anatomic variations were identified in 28 (28%) patients. These included 9 duplicated nerves, 6 lateral accessory nerves, 8 medial displacement, and 5 lateral displacement. Brachial plexus anatomic variation was found in 34 (34%) patients. The most common variant configuration of a fused middle and inferior trunk was identified in 25 (25%) patients. Combined phrenic nerve and brachial plexus anatomic variation was demonstrated in 15 (15%) patients. The VA and SA groups consisted of 47 and 53 patients, respectively. Transient phrenic nerve injury with postoperative elevation of the ipsilateral hemidiaphragm was documented in 3 (6.4%) patients in the VA group and 6 (11.3%) patients in the SA group (P = 0.49). Permanent phrenic nerve injury was identified in 1 (2.1%) patient in the VA group (P = 0.47) and none in the SA group. Transient brachial plexopathy was encountered in 1 (1.9%) patient in the SA group (P = 1.0) with full recovery to normal function. Conclusions: Anatomic variability of the phrenic nerve and brachial plexus are encountered more frequently than previously reported. While the incidence of nerve injury is low, surgeons operating within the thoracic aperture should be familiar with variant anatomy to reduce postoperative complications.