A 44-year-old man comes to the office for evaluation of a neck lump. The patient first noticed the lump 6 months ago while he was shaving and says that it seems to be growing in size. He has no pain, shortness of breath, cough, hoarseness, or difficulty swallowing. The patient had Hodgkin lymphoma 20 years ago, which was successfully treated with radiation therapy to his chest and neck. Physical examination shows a firm mass in the left thyroid lobe. There is no lymphadenopathy. Serum TSH level is normal. Fine-needle aspiration biopsy reveals papillary thyroid cancer. A total thyroidectomy is performed. During an attempt to ligate the inferior thyroid artery, a nervous structure in close proximity is inadvertently damaged. Which of the following was most likely injured during the surgery?

Question

A 44-year-old man comes to the office for evaluation of a neck lump.  The patient first noticed the lump 6 months ago while he was shaving and says that it seems to be growing in size.  He has no pain, shortness of breath, cough, hoarseness, or difficulty swallowing.  The patient had Hodgkin lymphoma 20 years ago, which was successfully treated with radiation therapy to his chest and neck.  Physical examination shows a firm mass in the left thyroid lobe.  There is no lymphadenopathy.  Serum TSH level is normal.  Fine-needle aspiration biopsy reveals papillary thyroid cancer.  A total thyroidectomy is performed.  During an attempt to ligate the inferior thyroid artery, a nervous structure in close proximity is inadvertently damaged.  Which of the following was most likely injured during the surgery?

Quizplus · Accepted Answer

11ec160b_3570_5c6c_9249_e9796b994d46_MD0001_00 The inferior thyroid artery arises from the thyrocervical trunk, a branch of the subclavian artery. Along with the superior thyroid arteries (branches of the external carotid arteries), the inferior thyroid arteries provide blood to the thyroid gland and other structures of the anterior neck. From the thyrocervical trunk, the inferior thyroid artery courses deep to the internal jugular vein, vagus nerve, and common carotid artery before turning toward the thyroid. As it approaches the thyroid, the artery comes in close proximity to the recurrent laryngeal nerve. The recurrent laryngeal nerve is a branch of the vagus nerve that loops below the aortic arch on the left and below the subclavian artery on the right to provide motor innervation to the intrinsic muscles of the larynx (except the cricothyroid). During thyroid surgery, this nerve may be damaged due to its proximity to the inferior thyroid artery. Unilateral nerve injury often causes hoarseness, whereas bilateral injury may cause inspiratory stridor and respiratory distress due to complete vocal cord paralysis. (Choice A) The spinal accessory nerve (CN XI) exits the jugular foramen and courses on top of the levator scapulae muscle to innervate the sternocleidomastoid and trapezius muscles on either side. (Choice B) The ansa cervicalis is a loop of the cervical plexus that receives contributions from C1-C3. It courses deep to the sternocleidomastoid muscle and loops around the internal jugular vein. Branches from the ansa cervicalis innervate the sternohyoid, sternothyroid, and omohyoid muscles. (Choice C) The hypoglossal nerve (CN XII) exits the cranium through the hypoglossal canal and innervates all the muscles of the tongue except the palatoglossus. (Choice D) The phrenic nerve arises from the C3-C5 cervical nerves and innervates the diaphragm. The most common cause of iatrogenic phrenic nerve injury is cardiothoracic surgery, in which the nerve can be damaged where it passes between the pericardium and mediastinal pleura. Manifestations include diaphragmatic paralysis (inspiratory weakness). (Choice F) The superior cervical ganglion is part of the sympathetic nervous system. It can be injured by an expanding lung cancer at the superior pulmonary sulcus (Pancoast tumor), leading to Horner syndrome (ie, ipsilateral ptosis, miosis, and anhydrosis). (Choice G) The superior laryngeal nerve branches off the vagus nerve high in the neck and divides into an external branch, which supplies the cricothyroid muscle, and an internal branch, which provides sensation over the supraglottic area. The external branch of this nerve may be misligated during thyroid surgery due to its proximity to the superior thyroid artery. Educational objective: The recurrent laryngeal nerve travels in close proximity to the inferior thyroid artery and can be injured during thyroid surgery, resulting in vocal cord paralysis (eg, hoarseness). __________ References: Anatomical relationship between recurrent laryngeal nerve and inferior thyroid artery in thyroidectomy patients. (http://www.ncbi.nlm.nih.gov/pubmed/25671953) An applied anatomical study on the recurrent laryngeal nerve and inferior thyroid artery. (http://www.ncbi.nlm.nih.gov/pubmed/22124577)

A 44-Year-Old Man Comes to the Office for Evaluation of a Neck