Surgery of thyroid and parathyroids

Question 1

Embryology 1

Answer 1

• Thyroid begins as a diverticulum of the foramen cecum posterior to the tongue (second pharyngeal arch)
• It descends to the neck but is still connected via the thyroglossal duct (anterior to the hyoid bone) to the foramen cecum
• Inhibited descent of the thyroid can lead to lingual thyroid
• Thyroglossal duct cysts can occur if the thyroglossal duct doesn’t completely involute

Question 2

Embryology 2

Answer 2

• Parathyroid glands arise from the third (inferior glands) and fourth (superior glands) arches
• The thymus is also derived from the 3rd arch, and as it descends it pulls the parathyroid glands with it, which is why the 3rd arch glands are the inferior ones
• Inferior glands are more likely to have varied locations (may be w/ thymus or elsewhere)

Question 3

Surgical anatomy of the thyroid

Answer 3

• Most of the blood to thyroid is supplied by inferior thyroid artery
• Closely associated w/ common carotid, IJV, recurrent laryngeal n, superior laryngeal nerves parathyroids
• Remember: R recurrent wraps around subclavian, L recurrent wraps around aorta

Question 4

Indications for surgery 1

Answer 4

• Benign disease: solitary or hyper-functioning thyroid nodule, multinodular goiter, grave’s (if relapse after ATD/adverse reaction to ATD, failed/refused RAI, or young w/ desire to conceive), aerodigestive problems (pressure)
• Differentiated thyroid CA: papillary and follicular CA
• Poorly differentiated thyroid CA: medullary and anapestic thyroid CA

Question 5

Indications for surgery 2

Answer 5

• If there is increased uptake of RAI in a single region its probably a hyper-functioning nodule
• Multinodular goiters may present w/ pemberton’s sign: raising arms above hear leads to redness in face due to obstruction of venous drainage (from pressure of the goiter)
• For pts w/ graves: first make them euthyroid, then give BBs, then super saturated potassium iodine (to reduce vascularity and shrink gland)

Question 6

Risks of surgery (total thyroidectomy)

Answer 6

• Recurrent laryngeal nerve injury: permanent damage is <1%, temporary damage more common
• Hypoparathyroidism: post op permanent hypoparathyroidism occurs in 5-15% of pts, this leads to hypocalcemia
• Causes of this: venous congestion, inadvertent removal, inability to preserve blood supply
• Thyroid storm: massive efflux of T3/T4 (from damage to gland) causes severe hyperthyroidism
• Making pt euthyroid/BBs/SSKI before surgery reduces the risk of thyroid storm greatly
• Life threatening hyper metabolic state: fever, respiratory distress, tachycardia/arrhythmias, high output CHF, hypotension and shock

Question 7

Primary hyperparathyroidism surgery

Answer 7

• Do sestamibi scan: radioactive dye is picked up by adenomas and helps to localize them
• Can also do ultrasound and MRI
• Intraoperative monitoring: PTH after 10 min should drop significantly (T1/2 is 5 min)