Session 11: Self-Study

Question 1

How do we test the function of the thyroid gland?

Answer 1

Thyroid function tests TSH, T3 and T4 levels

Question 2

What is the first-line imaging choice when investigating thyroid pathology like thyroid goitre or lump?

Answer 2

Ultrasound

Question 3

Where are the parathyroid glands in relation to the thyroid gland? How many are there, and what is their function?

Answer 3

Two paired endocrine glands positioned behind left and right lobes of the thyroid gland. Usually 4 in total. It is found within the fascia surrounding the thyroid gland but are separate. Produce PTH and calcitonin that is key in the regulation of calcium levels.

Question 4

What is a pyramidal lobe?

Answer 4

A third thyroid lobe due to persistent remnant of the thyroglossal duct which develops into thyroid gland tissue. This is failure of fusion of the distal part of the thyroglossal duct.

Question 5

Why does the thyroid gland move up on swallowing?

Answer 5

Ensheathed in the pretracheal fascia which attaches to the hyoid bone. The hyoid bone elevates on swallowing and so will the thyroid gland. The posterior surface of the thyroid gland is also attached to the cricoid cartilage and trachea by a suspensory ligament. When the larynx elevates on swallowing so will the thyroid gland. Neck lumps that move with swallowing can be localised to the thyroid gland.

Question 6

What collection of muscles lie anteriorly the thyroid gland?

Answer 6

Infrahyoid muscles. They act to stabilise the larynx during its movement during swallowing alongside the suprahyoids.

Question 7

What is a thyroid ima and where might it be found? Why might this cause difficulties for surgical access to the airway?

Answer 7

An artery present in a very small proportion of people. If it is present it can arise from the brachiocephalic trunk or arch of aorta. It will ascend in front of the trachea to the isthmus. It presence may prove problematic if accessing the trachea for a surgical airway or during thyroidectomy. It can be a source of rapid bleeding if damaged and when cut can retract behind the mediastinum so difficult to reach and ligate.

Question 8

Which veins drain the thyroid gland and to which main vessels do they subsequently drain?

Answer 8

Superior and middle thyroid veins drain to IJV. Inferior thyroid vein drain to the left brachiocephalic vein.

Question 9

From which main arteries do each of the vessels arise (sup and inf thyroid arteries)?

Answer 9

Sup - first branch of the external carotid artery Inf - thyrocervical trunk from subclavian

Question 10

What are the nerves lying in close proximity to these arteries? What would be a consequence of their injury?

Answer 10

External branch of the sup laryngeal nerve supplying motor to the cricothyroid muscle is in close proximity to the superior thyroid artery. The inferior thyroid artery is in close proximity to the recurrent laryngeal nerve which supplies the motor to all the muscles of the larynx except cricothyroid muscle.

Question 11

A 25 year old woman visited her GP because of a swelling just beneath her hyoid bone. She informed the doctor that although the swelling was painless, she was worried because it seemed to be getting larger. The doctor referred her to the hospital where further examination revealed that the swelling was a fluid-filled soft tissue mass that moved up when the patient swallowed and stuck her tongue out. No other neck masses or lymphadenopathy were present. Lab tests showed absence of radioactive iodine in the swelling. What is the most probable cause of the swelling? Explain your answer, particularly in relation to the clinical findings.

Answer 11

Thyroglossal duct cyst. The lump is fluid-filled and move up on both swallowing AND tongue protrusion. It is painless and also no radioactive iodine reaching it meaning it is discontinuous with the actual thyroid gland.

Question 12

Why might you be concerned about lymphadenopathy in the neck, particularly in the context of a neck swelling?

Answer 12

Most often due to an infectious causes or secondary to malignancy spreading. Deep cervical lymph nodes receive drainage directly from head and neck structures deep in the neck so a neck lump could be the first sign of pathology of an underlying HNC.

Question 13

What cervical nerve roots contribute to the cervical plexus?

Answer 13

Anterior rami of C1-C4

Question 14

What is the ansa cervicalis; what roots of the plexus contribute to this and is it motor/sensory or mixed?

Answer 14

Loop of nerves formed by C1-C3 nerve roots. Entirely muscular and gives off supply to the infrahyoid muscles.

Question 15

What anatomical structure does the ansa cervicalis overlie anteriorly?

Answer 15

Anterior on or in the carotid sheath

Question 16

Broadly speaking what collection of msucles do the branches of the ansa cervicalis innervate?

Answer 16

Infrahyoid muscles

Question 17

Which nerve roots contribute to the phrenic nerve and what structure does it innervate?

Answer 17

C3-C5 C3 and C4 from cervical plexus and C5 from brachial plexus. Diaphragm

Question 18

What areas of the scalp, head and neck receive sensory inenrvation from the cervical plexus?

Answer 18

Question 19

What relationship does the posterior border of the SCM have to the sensory branches of the cervical plexus?

Answer 19

All sensory converge and emergy from around midpoint on the posterior border of SCM.

Question 20

What is Erb’s point and how might this be utilised clinically?

Answer 20

Nerve point of the neck is the midpoint of the posterior border of the SCM where you can anaesthetise and block the senosry branches.

Inadvertent involvment of the phrenic nerve may happen due to close proximity of this nerve which can cause temporary paralysis of hemidiaphragm. This means that such blocks are thus avoided in patients with significant respiratory disease.