c l i n i c a l f o l i o s : n a r r a t i v e





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Thyroid Anatomy: 4

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Two common variants are the presence of a pyramidal lobe extending upward from the isthmus and a thyroid ima artery ascending from below. The pyramidal lobe is a remnant of the track the thyroid followed in embryologic life from the foramen cecum at the base of the tongue, through the site of the future hyoid bone to its final location. Incomplete descent of the thyroid can be mistaken for a tumor. In the face of a high midline neck mass, it is imperative to document thyroid tissue in the normal location by scan before excision. The thyroid ima artery arises from any of the great vessels of the chest and neck.     

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Thyroid Anatomy: 5

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The larynx is innervated by branches of the vagus nerve (cranial nerve X). All the muscles of the larynx except the cricothyroid (see larynx) are supplied by the recurrent laryngeal nerves. The terminal portion of this nerve passes beneath the inferior pharyngeal constrictor to enter the larynx behind the articulation of the inferior cornu of the thyroid cartilage with the cricoid cartilage. Recurrent laryngeal nerve injury results in paralysis of the vocal cord in a relatively adducted position. Bilateral recurrent nerve injury during total thyroidectomy may result in acute postoperative airway obstruction.

It is important to do pre- and postoperative laryngoscopy to document vocal cord function. The superior laryngeal nerve arises from the nodose ganglion of the vagus just outside the jugular foramen at the base of the skull and passes diagonally downward close to the sides of the larynx. It sends a sensory branch through the thyrohyoid membrane and continues as a motor branch to the cricothyroid muscle and inferior constrictor. The cricothyroid muscle maintains tension on the vocal cords. Injury to the superior laryngeal nerve results in loss of timbre, endurance and high range singing capability.  

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Thyroid Anatomy: 6

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The recurrent laryngeal nerve on the right arises from the vagus at the level of the subclavian artery, passes beneath the artery and ascends near the trachea-esophageal groove (see below). The left recurrent laryngeal arises at the level of the aortic arch and passes beneath the aorta just distal to the ligamentum arteriosum and also ascends near the left T-E groove.      

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This page was last modified on 12/10/1998.