Peripheral Nerve Anatomy Revisited: Modern Requirements for Neuroimaging and Microsurgery.

Detailed anatomic investigation of peripheral nerve topography underlies the correct application of intraoperative neuromonitoring (IONM) and ultrasonography, both well-established methods to prevent nerve palsy during surgical operations and to elucidate pathomechanisms in disease. In this study, we analyzed the anatomy of selected peripheral nerves in the head and neck regions to improve the outcome of endocrine and migraine surgeries. Anatomic dissections of 204 hemilarynges were performed to study the topography of the inferior laryngeal nerve (ILN). Measurements were taken from the lower rim of the cricoid and from the Zuckerkandl tubercle to the beginning of the furcation of the ILN. For the analysis of peripheral nerves contributing to migraine pathogenesis, 22 hemifaces were investigated by dissection and ultrasonography. The supratrochlear and supraorbital nerves and their relationship to the corrugator supercilii muscle are described. For identification of the ILN, the cricoid offers a suitable intraoperative landmark. A single branch existed in 5% of specimens on the left side and in 3% on the right side. Bifurcation was present in 72.5% and 62% and trifurcation in 18% and 29% of cases, respectively. IONM signals from the vagus nerve were positive if derived proximal to and negative if derived distal to the branching off of a nonrecurrent ILN (nrILN). By ultrasonographic identification of a brachiocephalic trunk, an nrILN could be excluded. For migraine surgery, possible compression points of the supratrochlear and supraorbital nerves were identified, and a workflow algorithm for ultrasound visualization of these nerves is provided. Anat Rec, 302:1325-1332, 2019. © 2019 Wiley Periodicals, Inc.