How does normal thyroid parenchyma appear on ultrasound?
Homogeneous medium level echoes
What is the pyramidal lobe of the thyroid?
Normal variant extending superior to the isthmus
How do the strap muscles of the neck appear on ultrasound?
Sternohyoid and sternothyroid
Sonolucent bands along the anterior surface of the thyroid gland
Where is the common carotid artery and the internal jugular vein in relation to the thyroid lobes?
Directly lateral to the thyroid lobes with the internal jugular vein lateral to the carotid artery
What muscle is posterior to the thyroid?
Longus colli muscle
Wedge shaped sonolucent structure adjacent to the cervical vertebrae
What is the minor neurovascular bundle composed of?
Recurrent laryngeal nerve and inferior thyroid vessels
Are the parathyroid glands typically visualized with ultrasound?
NO - due to their small size
How does the trachea appear on ultrasound?
Midline, characteristic curvilinear reflecting surface with associated reverberation artifact
How does the esophagus appear on ultrasound?
Transverse – target sign
Usually hidden by the trachea
Where does the thyroid arterial supply come from?
Superior thyroid artery - from external carotid artery
Inferior thyroid artery - from thyrocervical trunk
Where does the venous blood from the thyroid drain into?
Internal jugular vein via the superior and middle thyroid veins
Innominate veins via inferior thyroid veins
Which glands regulate thyroid hormones?
Thyroid
Pituitary
Hypothalamus
Where is TSH produced?
Pituitary
Stimulates the thyroid to produce thyroid hormones
What is usually the first indication of hypothyroidism?
Increase in TSH
Which gland regulates the pituitary gland?
Hypothalamus
What is the percent of the US population with evidence of nodular thyroid disease?
50% of the United States population
What is the overall incidence of cancer in patients with thyroid nodules?
10–13%
What is the most commonly encountered benign thyroid nodule?
Follicular adenoma
What can commonly occur within these benign nodules resulting in cystic thyroid nodules?
Hemorrhage or necrosis
What are risk factors for thyroid cancer?
Age – 60yo
Head and neck irradiation
Family history of thyroid cancer
What are physical findings of thyroid cancer?
Recent palpable neck mass Mass is firm and nontender Mass moves with swallowing Enlarged cervical lymph nodes Hoarseness Trouble swallowing or breathing
What is the most common primary thyroid cancer?
Papillary carcinoma
How does papillary carcinoma appear on ultrasound?
Hypoechoic mass, with possible calcifications
What is the major route for the spread of papillary carcinoma?
Through the lymphatics to nearby cervical lymph nodes
What accounts for 10 to 20% of thyroid cancers?
Follicular carcinoma
How do follicular cancers tend to spread?
Via the bloodstream
What does medullary carcinoma typically secrete?
Calcitonin
Associated with multiple endocrine neoplasia syndrome
How does anaplastic carcinoma behave?
Aggressive, rapidly invades surrounding tissue causing airway obstruction
How are thyroid masses clinically evaluated?
Fine needle aspiration with cytologic evaluation
When should FNA be considered?
> 1 cm with microcalcifications > 1.5 cm that is predominantly solid > 2 cm that has mixed components Nodule demonstrating growth Nodule with ipsilateral abnormal lymph nodes
How is ultrasound used to differentiate thyroid nodules from other cervical masses?
Differentiate from cystic hygromas, glossal duct cysts, or enlarged lymph nodes
Which factors improve the positive predictive value of ultrasound in determining the malignant nature of a nodule?
Composition
Echogenicity
Margination
Calcification
What aspect of composition is associated with higher risk of malignancy?
The solid component
How do the margins appear in malignant lesions?
The regular or poorly defined margins
Which calcifications are indicative of a malignancy?
Fine and punctate
What are the features associated with thyroid cancer?
Microcalcifications Solid hypoechogenicity Irregular margins Absence of halo Intranodule central vascularity More tall than wide
Which conditions cause diffuse thyroid disease?
Chronic autoimmune thyroiditis (Hashimoto’s)
Adenomatous goiter
Graves’ disease
How does Hashimoto’s thyroiditis appear on ultrasound?
Hypoechoic diffuse enlargement with a coarse parenchymal echotexture
What is a goiter?
Enlarged thyroid gland that may be diffuse or nodular
How is thyroid function in different types of goiters?
Normal – nontoxic goiter
Overactive – toxic goiter
Underactive – hypothyroid goiter
What is the most common cause of a goiter worldwide?
Iodine deficiency
How do goiters appears sonographically?
Multiple discrete nodules
Diffuse parenchymal inhomogeneity
Mixed echogenicity without normal tissue
What is Graves disease?
Autoimmune disorder characterized by hyperthyroidism due to circulating antibodies
How does Graves disease cause hyperthyroidism?
Thyroid antibodies bind to activate thyrotropin receptors causing the thyroid gland to grow causing an increased production of thyroid hormones
How does the thyroid appear on ultrasound in Graves’ disease?
Diffusely hypoechoic and inhomogeneous
How does a parathyroid adenoma appear on ultrasound?
Oval hypoechoic mass posterior to the thyroid gland
What is the most common type of hyperparathyroidism?
Development of an adenoma associated with one of the parathyroid glands
How is primary hyperparathyroidism diagnosed?
Increased serum parathyroid hormone with increased serum calcium
Which condition develops secondary hyperparathyroidism?
Chronic renal failure because of increased amounts of serum phosphates
What stimulates parathyroid gland hyperplasia in secondary hyperparathyroidism?
Inability to synthesize vitamin D depresses the serum calcium level
What is the most common manifestation of multiple endocrine neoplasia, type 1?
Hyperparathyroidism resulting in hyperplasia of all four parathyroid glands
What are the salivary glands?
Exocrine glands that secrete saliva and amylase
Where are the sublingual glands located?
Beneath the tongue, anterior to submandibular glands
Where are the parotid glands located?
Anterior to the ear wrapped around the mandibular ramus
Where are the submandibular glands located?
Beneath the jaw
Name the salivary glands.
Parotid
Sublingual
Submandibular
Which ducts are associated with each salivary gland?
Parotid - Stensen’s duct
Submandibular - Wharton’s duct
What are the diseases of the salivary glands?
Mumps Sjögren's syndrome Mucoceles Neoplasms Salivary duct calculus
What is the most common superficial midline neck mass in adolescents with an associated URI?
Thyroglossal duct cyst
What is a thyroglossal duct cyst?
Cystic dilatation of the thyroglossal duct which is a remnant of the thyroid gland migration from the pharyngeal epithelium
What is a branchial cleft cyst?
Solitary, predominantly cystic mass appearing on the lateral aspect of the neck at the angle of the mandible under the SCM
What is a cystic hygroma?
Congenital lymphatic malformation
75% occur in neck
How does a cystic hygroma appear on ultrasound?
Cystic multiloculated cervical mass that is evident at birth
What syndromes are associated with a cystic hygroma?
Turner syndrome
Down syndrome
Klinefelter syndrome
Trisomy 18 and 13
What are the vessels of the aortic arch?
Innominate artery
Left common carotid artery
Left subclavian artery
Is there a left innominate artery?
NO - only one innominate artery but bilateral innominate veins
At what level does the common carotid artery bifurcate?
Superior border of the thyroid cartilage
Where are the ICA and ECA located?
ICA – lateral and posterior
ECA – medial and anterior
Describe the waveforms of the ICA and ECA.
ICA – low resistance
ECA – high resistance
What is the first branch of the ICA and the ECA?
ICA – ophthalmic artery
ECA – superior thyroid artery
Where is the internal jugular vein in relation to the common carotid artery?
Lateral
What do the internal jugular vein and subclavian vein drain into?
The innominate or brachiocephalic veins bilaterally