Recurrent laryngeal nerve

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Evolved into a nuisance to thyroid surgeons.

The thyroid gland and its relationships from Grays 1918.

The thyroid develops, embryologically, in the floor of the mouth rather than where it ends up, the base of the neck. As it moves down, it leaves a track, in which thyroglossal cysts are sometimes found, and if small, best left

The branch of the vagus nerve which innervates the larynx reaches it by peculiar routes. Having been carried past the larynx by the development of the arteries it returns up the neck. While this is merely a small curiosity in most mammals, in the giraffe it is a rather strikingly ridiculous wiring pattern for anything that was designed, while being perfectly understandable in terms of evolution.

The recurrent laryngeal nerve is at risk during thyroid surgery, and must be identified and preserved. Inspection of the vocal cords by laryngoscopy a while after surgery, before discharge, is usual as well, in order to document that the nerve has not been damaged. Inspection before thyroid surgery is also prudent, since there is a small incidence of unilateral laryngeal n. palsy in people who show no signs of it, greater in those about to have thyroid surgery. Bailey & Love indicate that a laryngeal n palsy is highy indicative of thyroid cancer.