Session 11: Anatomy of the Thyroid Gland & Head and Neck Cancers Flashcards
Vertebral location of the thyroid gland.
C5 to T1
Explain the anatomical position of the thyroid in relation to other structures.
Lies posterior to the sternohyoid and sternohyoid muscles.
It wraps around the cricoid cartilage and superior tracheal rings.
Found inferior to the thyroid cartilage and the gland is in the visceral compartment of the neck along with the trache, oesophagus and the pharynx.
The compartment is bound by pretracheal fascia.
During development where does the thyroid gland initially form?
Near the base of the tongue in the primitive pharynx.
It then descends down the neck to lie in its adult anatomical position.
As the thyroid gland descends during development, what does it move through?
The thyroglossal duct.
What happens to the thyroglossal duct?
It will normally fuse and regress.
What happens in case the duct doesn’t fuse correctly?
It may happen in around 50% individuals that the distal portion of the duct contines as a pyramidal lobe.
This becomes an extra piece of thyroid tissue but has no clinical consequence.
What are thyroglossal cysts?
If other portions of the duct persist that is not the distal portion.
How do thyroglossal cysts present?
As a mass in the midline of the neck.
Can be excised surgically.
Anterolateral structures to the thyroid gland.
Sternothyroid
Superior belly of omohyoid
Sternohyoid
Posterolateral structures to the thyroid gland.
Carotid sheath with common carotid, internal jugular vein and the vagus nerve.
Posteromedial structures to the thyroid gland.
Larynx
Trachea
Pharynx
Oesophagus
External laryngeal nerve
Recurrent laryngeal nerve
Blood supply of the thyroid gland.
Superior and inferior thyroid arteries.
From what and where does the superior thyroid artery arise?
First branch of the external carotid artery.
After it arises it descends toward the thyroid gland.
What does the superior thyroid artery supply?
Superior and anterior portions of the thyroid gland.
What does the inferior thyroid artery arise from?
The thyrocervical trunk which is a branch of the subclavian artery.
Then travels superomedially to reach the inferior pole of the thyroid.
What does the inferior thyroid artery supply?
The posteroinferior aspect of the gland.
What is the thyroid ima artery?
In 10% of people there is an extra artery called the thyroid ima artery.
Comes from the brachiocephalic trunk of the arch of the aorta.
Venous drainage of the thyroid.
Superior, middle and inferior thyroid veins which form a venous plexus.
What does the inferior, middle and superior thyroid veins draini into?
Superior and middle -> internal jugular veins
Inferior -> brachiocephalic vein
Innervation of the thyroid gland.
Branches derived from the sympathetic trunk.
These nerves do not control the endocrine secretion as they are controlled by the pituitary gland.
Common sites for cancer in head and neck.
Lip/oral cavity
Pharynx
Larynx
Thyroid
What is most common type of cancer in head and neck?
Squamous cell carcinoma (90%)
Risk factors of head and neck cancers.
Alcohol
Tobacco (including chewing tobacco)
Age (older patients)
Male
Betel nut chewing
Dental hygiene
Long term exposeure to sunglight or sunbeds
What is an additional risk factor especially for oropharyngeal cancers?
HPV
What is an additional risk factor especially for nasopharyngeal cancers?
Epstein-Barr virus
Additional risk factors for thyroid cancer.
Irradiation exposure (radioactive iodine e.g.)
Family history like FAP
Staging of head and neck cancers.
TNM
Clinical diagnosis of head and neck cancers.
History
Through clinical examination and biopsy.
Imaging
Endoscopic investigations if nasal cavity, pharynx and larynx.
Why is staging important in head and neck cancers?
To determine appropriate treatment.
Early stage H&N cancer treatment.
Usually done by surgical removal or radiotherapy
More advanced H&N cancers treatment.
Surgery and adjuvant chemoradiation.
How might surgery be done in H&N cancers?
Microsurgical techniques like lasers.
Radical neck dissections where all ipsilateral lymph nodes, CN XI, IJV and SCM are removed.
Implications of radical neck dissection.
Difficulty eating, drinking, speaking and breathing.
General clinical presentation of head and neck cancers.
Unexplained painful and/or mucosal ulceration or lesion (leukoplakia, erythroplakia or a lump) within the oral cavity.
Unexplained hoarseness of voice
Dysphagia
Odynophagia
Otalgia
Cervical lymphadenopathy
Clinical presentation of lip/oral cavity cancer.
Lump
Pain included referred pain to the ear.
Fixation of tongue
Dysphagia
Odynophagia
Clinical presentation of pharynx cancer.
Lump
Pain + otalgia
Dysphagia
Odynophagia
Weight loss
Clinical presentation of larynx cancer.
Dysphonia
Dysphagia
Otalgia
Globus sensation (feel like something is stuck in the throat)
Neck lump
Weight loss
Cachexia
Types of thyroid cancers.
Papillary adenocarcinoma
Follicular adenocarcinoma
Medullary carcinoma
Anaplastic carcinoma
Most common type of thyroid cancer.
Papillary adenocarcinoma
Treatment of thyroid cancer.
Thyroidectomy
Radioactive iodine
Chemoradiotherapy
What type of imaging is used in laryngeal and pharyngeal cancers?
Usually CT first
Investigation of thyroid cancer.
Ultrasound
Biopsy
