The ‘false’ non‐recurrent inferior laryngeal nerve

Background A communication between the middle cervical sympathetic ganglion (MCSG) and the inferior laryngeal nerve (ILN) has been described. The anastomotic branch (sympathetic–inferior laryngeal anastomotic branch; SILAB) is usually thin, but is sometimes larger and has the same diameter as the ILN. The purpose of this study was to evaluate prospectively the frequency of this condition and its implications during neck exploration. Methods From November 1998 to October 1999, 791 neck explorations were performed: 677 for thyroid, 99 for parathyroid and 15 for concomitant lesions. Some 1253 ILNs were dissected: 656 (52·3 per cent) on the right and 597 (47·7 per cent) on the left side. Results The ILN was identified in all cases. On the right side a non‐recurrent ILN (NRILN) was found in three patients (0·5 per cent) and a large SILAB in ten (1·5 per cent). No anomalous branch was found on the left side. The SILAB originated from the superior cervical sympathetic ganglion (SCSG) in two patients and directly from the sympathetic chain (SC) above the MCSG in eight. No branch originating from the MCSG was found. The SILAB connected with the ILN less than 2 cm from the cricoid in all patients. Conclusion The SILAB may originate not only from the MCSG but also from the SCSG and directly from the SC. When the SILAB is as large as the ILN, it could be mistaken for a NRILN. Before concluding that the anomalous branch is a NRILN, one should check if it originates from the vagus or from the cervical sympathetic system. Awareness of this anatomical condition during neck exploration may help the surgeon to avoid injuries of an ILN running in the usual pathway. © 2000 British Journal of Surgery Society Ltd