Thyroid and Parathyroid Glands — MCQs
Which of the following is used in investigating a parathyroid pathology?
Inferior thyroid artery supplies which of the following structures? 1. Thyroid 2. Parathyroid 3. Esophagus 4. Thymus
All of the following are branches of the external carotid artery except?
The labia majora develop from which embryological structure?
The arterial supply of the submandibular gland is
Which nerve is most likely injured during a thyroidectomy?
Upward movement of the thyroid gland is prevented due to?
Adam's apple in males is formed by the
Chvostek sign could be seen after -
Most sensitive investigation for preoperative localization of abnormal parathyroid glands is
Thyroid and Parathyroid Glands Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is used in investigating a parathyroid pathology?
- A. CT scan
- B. Gallium scan
- C. Thallium scan
- D. Tc-99m Sestamibi scan (Correct Answer)
Explanation: ***Tc-99m Sestamibi scan*** - **Tc-99m Sestamibi (MIBI)** is the **current gold standard** nuclear medicine imaging for parathyroid pathology, particularly for localizing **parathyroid adenomas**. - Sestamibi is taken up by **hyperfunctioning parathyroid tissue** and retained longer in adenomas compared to normal thyroid tissue due to differences in mitochondrial activity and washout rates. - Often performed as a **dual-phase study**: early images show both thyroid and parathyroid uptake, while delayed images (2-3 hours) show retention in parathyroid adenomas with washout from thyroid tissue. - Frequently combined with **SPECT/CT** for precise anatomical localization, improving surgical planning. - **Sensitivity: 80-90%** for single adenomas, with reported accuracy up to 95% when combined with ultrasound. *CT scan* - While **4D-CT** (multi-phase CT) has emerged as a useful adjunct for parathyroid localization, CT is **not a nuclear medicine technique** and is not typically the first-line imaging modality. - CT scans are more useful for assessing **ectopic parathyroid glands** (mediastinal location), preoperative planning, or when nuclear medicine studies are inconclusive. *Gallium scan* - **Gallium-67 citrate scans** are used to detect tumors, infections, and inflammatory conditions but are **not specific for parathyroid pathology**. - Gallium has **no role** in modern parathyroid imaging. *Thallium scan* - **Thallium-201 scans** (alone or in Thallium-Technetium subtraction techniques) were used historically in the 1980s-1990s for parathyroid imaging. - These techniques have been **completely replaced** by Tc-99m Sestamibi, which offers superior image quality, better radiation dosimetry, and more convenient imaging protocols.
Question 2: Inferior thyroid artery supplies which of the following structures? 1. Thyroid 2. Parathyroid 3. Esophagus 4. Thymus
- A. 1 and 2 only
- B. 1,2 and 3 (Correct Answer)
- C. 1,2 and 4 only
- D. 1,2,3 and 4
Explanation: ***1,2 and 3*** - The **inferior thyroid artery** is a branch of the **thyrocervical trunk** and supplies the **thyroid gland**, **parathyroid glands**, and the **cervical part of the esophagus** [1]. - It also gives branches to the **trachea** and **larynx** (via the inferior laryngeal artery). - These are the standard, consistently described structures supplied by this artery in anatomical texts. *1 and 2 only* - This option is incomplete as the inferior thyroid artery provides blood supply to more structures than just the thyroid and parathyroid glands. - It also supplies the **cervical portion of the esophagus** through its esophageal branches. *1,2 and 4 only* - This option is incorrect because the inferior thyroid artery does supply the **esophagus** (cervical part), which is missing from this option. - The **thymus** is primarily supplied by branches of the **internal thoracic artery**, not the inferior thyroid artery. *1,2,3 and 4* - This option is incorrect because the **thymus** is NOT a standard structure supplied by the inferior thyroid artery. - The thymus receives its blood supply primarily from the **internal thoracic artery** (anterior mediastinal branches) and sometimes from the **superior thyroid artery**. [1] - The inferior thyroid artery's distribution includes thyroid, parathyroid, esophagus, trachea, and larynx—but not the thymus.
Question 3: All of the following are branches of the external carotid artery except?
- A. Superior thyroid artery
- B. Transverse cervical artery (Correct Answer)
- C. Ascending pharyngeal artery
- D. Superficial temporal artery
Explanation: ***Transverse cervical artery*** - The **transverse cervical artery** is a branch of the **thyrocervical trunk**, which itself originates from the **subclavian artery**, not the external carotid artery. - It supplies muscles in the neck and shoulder region. *Superior thyroid artery* - The **superior thyroid artery** is typically the first branch of the **external carotid artery**. - It supplies the **thyroid gland** and adjacent structures in the neck. *Ascending pharyngeal artery* - The **ascending pharyngeal artery** is the only **medial branch** of the **external carotid artery**. - It supplies the **pharynx**, prevertebral muscles, and middle ear. *Superficial temporal artery* - The **superficial temporal artery** is one of the **two terminal branches** of the **external carotid artery**, forming in the parotid gland. - It supplies the scalp in the temporal region and is palpable anterior to the ear.
Question 4: The labia majora develop from which embryological structure?
- A. Urogenital folds
- B. Labioscrotal swellings (Correct Answer)
- C. Müllerian ducts
- D. Genital tubercle
Explanation: ***Labioscrotal swellings*** - The **labia majora** develop from the **labioscrotal swellings**, which are paired bilateral structures that appear around week 9-10 of development [1]. - These swellings arise lateral to the urogenital folds and do not fuse in females, forming the labia majora. - In males, these same structures fuse in the midline to form the scrotum. - This is a key example of **sexual differentiation** in embryological development [1]. *Urogenital folds* - The urogenital folds form the **labia minora** in females, not the labia majora. - In males, these folds fuse to form the ventral aspect of the penis and enclose the penile urethra. *Genital tubercle* - The genital tubercle forms the **clitoris** in females and the **glans penis** in males. - It does not contribute to the formation of the labia majora. *Müllerian ducts* - The Müllerian (paramesonephric) ducts form the **upper vagina, uterus, and fallopian tubes** in females. - They are internal structures and do not contribute to external genitalia like the labia majora.
Question 5: The arterial supply of the submandibular gland is
- A. Facial artery (Correct Answer)
- B. Lingual artery
- C. External carotid artery
- D. Sublingual arteries
Explanation: ***Facial artery*** - The **facial artery** gives off several branches that supply the submandibular gland, including the glandular branches. - It arises from the **external carotid artery** and reaches the gland by looping over the posterior belly of the digastric muscle. *Lingual artery* - The **lingual artery** primarily supplies the tongue and floor of the mouth. - While in close proximity, it does not directly provide the main arterial supply to the submandibular gland. *External carotid artery* - The **external carotid artery** is the parent vessel from which the facial artery (and lingual artery) originate. - It does not directly supply the submandibular gland; rather, its branches do. *Sublingual arteries* - **Sublingual arteries** are branches of the lingual artery and primarily supply the sublingual gland and floor of the mouth. - They do not contribute significantly to the arterial supply of the submandibular gland.
Question 6: Which nerve is most likely injured during a thyroidectomy?
- A. Hypoglossal
- B. Phrenic nerve
- C. Superior laryngeal
- D. Recurrent laryngeal (Correct Answer)
Explanation: ***Recurrent laryngeal*** - The **recurrent laryngeal nerves** are highly susceptible to injury during thyroidectomy due to their close anatomical proximity to the **thyroid gland** and their relatively superficial course within the operative field. - Injury to these nerves can lead to **vocal cord paralysis**, resulting in **hoarseness** or, in cases of bilateral injury, severe airway compromise. *Hypoglossal* - The **hypoglossal nerve** (CN XII) innervates the muscles of the tongue and is located more superiorly and medially, well outside the typical dissection planes for a thyroidectomy. - Damage to this nerve would primarily affect **tongue movement** and speech articulation, symptoms not commonly associated with thyroid surgery complications. *Phrenic nerve* - The **phrenic nerve** innervates the diaphragm and is situated deep in the neck and thorax, far from the thyroid surgical field. - Injury during thyroidectomy is extremely rare and would lead to **diaphragmatic paralysis**, causing respiratory difficulties. *Superior laryngeal* - The **superior laryngeal nerve** descends alongside the superior thyroid artery and typically divides into internal and external branches; the **external branch** is at risk during ligation of the superior thyroid pedicle. - While it can be injured, the **recurrent laryngeal nerve** is more frequently and severely affected, particularly its motor function to the intrinsic laryngeal muscles, which is most critical for voice production.
Question 7: Upward movement of the thyroid gland is prevented due to?
- A. Berry ligament (Correct Answer)
- B. Sternothyroid muscle
- C. Thyrohyoid membrane
- D. Pretracheal fascia
Explanation: ***Berry ligament*** - The **Berry ligament** (or suspensory ligament of Berry) firmly anchors the thyroid gland to the **trachea** and **cricoid cartilage** [1]. - This strong fibrous connection prevents the thyroid gland from moving upward, thus ensuring its stability [1]. *Sternothyroid muscle* - The **sternothyroid muscle** is an infrahyoid muscle that depresses the hyoid bone and larynx. - While it covers a portion of the thyroid gland, its primary function is **laryngeal movement**, not to prevent upward displacement of the thyroid. *Thyrohyoid membrane* - The **thyrohyoid membrane** connects the thyroid cartilage to the hyoid bone. - Its main role is to provide a broad attachment for muscles involved in **laryngeal elevation and depression**, not to stabilize the thyroid gland itself. *Pretracheal fascia* - The **pretracheal fascia** encloses the thyroid gland and creates a capsule around it, but it is not the primary structure preventing upward movement [2]. - It helps to contain the gland but does not provide the specific strong anatomical anchor that prevents its superior migration.
Question 8: Adam's apple in males is formed by the
- A. Hyoid bone
- B. Epiglottis cartilage
- C. Thyroid cartilage (Correct Answer)
- D. Cricoid cartilage
Explanation: ***Thyroid cartilage*** - The "Adam's apple" is anatomically known as the **laryngeal prominence**, which is formed by the anterior-most projection of the **thyroid cartilage**. - This prominence is typically more pronounced in males due to **hormonal influences** during puberty that lead to a larger larynx and vocal cords. *Hyoid bone* - The **hyoid bone** is a U-shaped bone located superior to the larynx that supports the tongue, but it does not form the "Adam's apple." - It is unique because it is the only bone in the human body not articulating with any other bone. *Epiglottis cartilage* - The **epiglottis** is a leaf-shaped elastic cartilage that covers the entrance to the larynx during swallowing to prevent food and liquid from entering the trachea. - It is positioned posterior to the thyroid cartilage and is not externally visible as the "Adam's apple." *Cricoid cartilage* - The **cricoid cartilage** is a complete ring of hyaline cartilage located inferior to the thyroid cartilage, forming the base of the larynx. - While it's a part of the larynx, it does not form the anterior projection known as the "Adam's apple."
Question 9: Chvostek sign could be seen after -
- A. Total Thyroidectomy (Correct Answer)
- B. Subtotal Thyroidectomy
- C. Heller's Cardiomyotomy
- D. Gastrojejunostomy
Explanation: ***Total Thyroidectomy*** - A total thyroidectomy involves the removal of the entire thyroid gland, which can inadvertently lead to the removal or damage of the **parathyroid glands** as well. - Damage to the parathyroid glands causes **hypoparathyroidism**, leading to **hypocalcemia**, which is characterized by neuromuscular excitability manifesting as a **Chvostek sign**. *Subtotal Thyroidectomy* - In a subtotal thyroidectomy, only a portion of the thyroid gland is removed, leaving some functional parathyroid tissue intact. - This procedure usually preserves enough parathyroid function to prevent severe **hypocalcemia** and the manifestation of a Chvostek sign. *Heller's Cardiomyotomy* - Heller's cardiomyotomy is a surgical procedure performed to treat **achalasia**, involving the cutting of muscle fibers in the esophagus. - This procedure does not involve the neck region or the parathyroid glands and therefore has no direct association with calcium regulation or the **Chvostek sign**. *Gastrojejunostomy* - A gastrojejunostomy is a surgical procedure that creates a bypass between the stomach and the jejunum, typically performed for conditions like gastric outlet obstruction or as part of bariatric surgery. - This operation is limited to the abdominal cavity and has no direct impact on calcium metabolism or the parathyroid glands that would elicit a **Chvostek sign**.
Question 10: Most sensitive investigation for preoperative localization of abnormal parathyroid glands is
- A. Neck ultrasound
- B. (99mTc) labelled Sestamibi isotope scan (Correct Answer)
- C. CT scan
- D. MRI
Explanation: ***(99mTc) labelled Sestamibi isotope scan*** - This scan uses a **radioactive tracer** that is preferentially taken up and retained by hyperfunctioning parathyroid tissue, making it highly sensitive for identifying **abnormal parathyroid glands**, especially parathyroid adenomas. - It is particularly useful for detecting **ectopic parathyroid glands** and in cases of persistent or recurrent hyperparathyroidism. *Neck ultrasound* - While useful for localizing parathyroid glands, its sensitivity can be limited by **operator dependence**, gland size, and location (e.g., retrosternal). - It is generally good for initial screening but not as sensitive as Sestamibi for identifying all abnormal glands, especially those located in challenging areas. *CT scan* - CT scans can visualize larger parathyroid adenomas, but their sensitivity is lower than Sestamibi scans for smaller lesions or those with **atypical locations**. - It is often used as a **second-line imaging modality** when Sestamibi is inconclusive or to complement findings. *MRI* - MRI can provide detailed anatomical information and identify parathyroid glands, but its sensitivity for detecting abnormal parathyroid tissue is generally **comparable to or slightly less** than CT and inferior to Sestamibi scanning. - It may be considered in cases of unclear findings from other modalities or when radiation exposure is a concern.
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