Blood supply of the terminal part of the external branch of the superior laryngeal nerve

The external laryngeal nerve (ELN) carries motor fibers to the cricothyroid and inferior pharyngeal muscles. Damage to the nerve may cause symptoms such as a monotone voice. One reason for these symptoms may be nerve injury due to inadvertent stretching, ligation or transaction of the nerve during the dissection of the superior pole of the thyroid gland. We hypothesized a new reason for the symptoms, an insufficient arterial blood supply to the nerve, and investigated this hypothesis. From 36 larynges, 52 sides (26 right and 26 left) were dissected under a surgical Zeiss-OpM1 microscope. The arterial branch to the external branch of the superior laryngeal nerve originated from the posterior glandular branch of the superior thyroid artery in 26 (50 %) sides, from the anterior glandular branch in 23 (44.23 %) sides, from its trunk on one (1.92 %) side, from the infrahyoid branch on one (1.92 %) side and from the bifurcation of the superior thyroid artery at the level of separation of the anterior and posterior glandular branches on one (1.92 %) side. Devascularization of the ELN may lead to dysfunction, so this nerve's varied blood supply should be kept in mind when invasive procedures are performed in this region.