Mediastinum — MCQs
Anterior Mediastinal nodes are included in which level of lymph nodes?
The lower border of the pharynx is the level of:
What is the correct statement about thymoma?
Which arch artery contributes to the formation of the aortic arch that influences the course of the left recurrent laryngeal nerve?
Which of the following statements regarding axillary lymph nodes is incorrect?
In an emergency tracheostomy, which structures are least likely to be damaged?
A patient presents with a mediastinal mass and is diagnosed with pure red cell aplasia. What is the most probable underlying cause?
Which of the following is not seen in the anterior mediastinum?
NOT a content of superior mediastinum
Which structures are located anterior to the transverse sinus?
Mediastinum Indian Medical PG Practice Questions and MCQs
Question 1: Anterior Mediastinal nodes are included in which level of lymph nodes?
- A. I
- B. V
- C. VI (Correct Answer)
- D. VII
Explanation: ***VI*** - Level VI lymph nodes are the **prevascular and retrotracheal nodes** located in the **anterior mediastinum** [1]. - According to the **IASLC (International Association for the Study of Lung Cancer)** lymph node mapping system, Level 6 nodes are specifically classified as anterior mediastinal nodes [1]. - These include nodes anterior to the superior vena cava and ascending aorta, and nodes between the trachea and esophagus [1]. *I* - Level I lymph nodes are located in the **low cervical, supraclavicular, and sternal notch** regions. - These are **extra-thoracic nodes** and not part of the mediastinal compartments. - They represent the highest mediastinal, supraclavicular, and sternal notch nodes [1]. *V* - Level V lymph nodes are the **subaortic (aortopulmonary window)** nodes [1]. - These are located in the space between the **aorta and pulmonary artery**, lateral to the ligamentum arteriosum [1]. - While mediastinal, they are specifically in the aortopulmonary window, not classified as anterior mediastinal. *VII* - Level VII lymph nodes are the **subcarinal nodes** located below the carina in the **middle mediastinum** [1]. - These nodes are positioned in the space beneath where the trachea bifurcates into the main bronchi [1]. - They are classified as middle mediastinal nodes, not anterior mediastinal nodes.
Question 2: The lower border of the pharynx is the level of:
- A. C2
- B. C3
- C. C4
- D. C6 (Correct Answer)
Explanation: ***C6*** - The **pharynx** extends from the base of the skull to the inferior border of the **cricoid cartilage** [1]. - This anatomical landmark, the inferior border of the **cricoid cartilage**, is located at the level of the **C6 vertebra** [1]. *C2* - The C2 vertebra, also known as the **axis**, is significantly higher than the lower border of the pharynx. - It is involved in head rotation and forms part of the **atlantoaxial joint**. *C3* - The C3 vertebra is located higher in the cervical spine and is associated with structures like the hyoid bone, but not the lower pharyngeal border. - It is the approximate level of the **hyoid bone** [1]. *C4* - The C4 vertebra is typically at the level of the superior border of the **thyroid cartilage**, which is still superior to the lower pharynx. - This level is also associated with the bifurcation of the common carotid artery.
Question 3: What is the correct statement about thymoma?
- A. Chest X-ray is the investigation of choice for the diagnosis of thymoma.
- B. Thymoma is primarily located in the posterior mediastinum.
- C. Thymoma is the most common neoplasia of the thymus. (Correct Answer)
- D. Thymoma is usually asymptomatic and only occasionally causes symptoms.
Explanation: ***Thymoma is the most common neoplasia of the thymus.*** [1] - **Thymoma** is the most common primary tumor of the thymus, accounting for approximately **40-50% of anterior mediastinal masses** in adults. - It is a slow-growing tumor originating from the **epithelial cells** of the thymus [1]. *Chest X-ray is the investigation of choice for the diagnosis of thymoma.* - While a **chest X-ray** may show a widened mediastinum or an anterior mediastinal mass, it is not the investigation of choice for definitive diagnosis or staging [2]. - **CT scan** of the chest with contrast is the preferred imaging modality for evaluating thymomas, providing better anatomical detail and assessing invasiveness [2]. *Thymoma is typically asymptomatic and rarely causes any symptoms.* - Approximately **30-50% of patients with thymoma are asymptomatic** at diagnosis, with the tumor discovered incidentally on imaging [2]. - However, the remaining **50-70% of patients present with symptoms** related to **mass effect** (e.g., chest pain, dyspnea, cough) or **paraneoplastic syndromes** like myasthenia gravis, pure red cell aplasia, or hypogammaglobulinemia [2]. - Therefore, it is incorrect to say thymoma "rarely" causes symptoms. *Thymoma is primarily located in the posterior mediastinum.* - **Thymoma** is characteristically located in the **anterior mediastinum**, which is the most common site for thymic tissue. - Tumors primarily found in the posterior mediastinum are more commonly **neurogenic tumors**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 571-574. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 572-574.
Question 4: Which arch artery contributes to the formation of the aortic arch that influences the course of the left recurrent laryngeal nerve?
- A. 4th arch (Correct Answer)
- B. 3rd arch
- C. 5th arch
- D. 2nd arch
Explanation: ***4th arch*** - The **left fourth aortic arch artery** gives rise to the **aortic arch** distal to the origin of the left subclavian artery. - The left recurrent laryngeal nerve hooks around the **ductus arteriosus** (a remnant of the 6th arch artery) and the aortic arch, making its course dependent on the development of the 4th aortic arch [1]. *3rd arch* - The **third aortic arch arteries** primarily contribute to the formation of the common carotid arteries and the proximal part of the internal carotid arteries. - These arteries are located superior to the structures that influence the recurrent laryngeal nerve's path. *5th arch* - The **fifth aortic arch arteries** are **rudimentary** or absent in humans. - They do not significantly contribute to the formation of major arterial structures in the adult, nor do they influence the recurrent laryngeal nerve. *2nd arch* - The **second aortic arch arteries** give rise to the stapedial arteries, which usually regress. - They are not involved in the formation of the great vessels in the mediastinum or the course of the recurrent laryngeal nerve.
Question 5: Which of the following statements regarding axillary lymph nodes is incorrect?
- A. Posterior group lies along subscapular vessels
- B. Lateral group lies along lateral thoracic vessels (Correct Answer)
- C. Apical group is terminal lymph nodes
- D. Apical group lies along axillary vessels
Explanation: ***Lateral group lies along lateral thoracic vessels*** - The **lateral group** of axillary lymph nodes is located along the **axillary vein**, receiving lymph primarily from the upper limb [1]. - The **lateral thoracic vessels** are associated with the central and posterior groups of axillary lymph nodes, not the lateral group. *Posterior group lies along subscapular vessels* - The **posterior (subscapular) group** of axillary lymph nodes is indeed located along the **subscapular vessels**. - This group receives lymph from the posterior wall of the trunk and the posterior shoulder region. *Apical group is terminal lymph nodes* - The **apical group** (also known as the subclavian group) is considered the **terminal lymph nodes** of the axilla. - Lymph from all other axillary nodes eventually drains into the apical group before continuing to the supraclavicular nodes and then into the subclavian lymphatic trunk [2]. *Apical group lies along axillary vessels* - The **apical group** of axillary lymph nodes is situated in the apex of the axilla, superior to the pectoralis minor muscle, and lies in close proximity to the **axillary vessels** [1]. - This location allows it to receive lymph from other axillary groups and drain into the supraclavicular lymph nodes.
Question 6: In an emergency tracheostomy, which structures are least likely to be damaged?
- A. Isthmus of the thyroid
- B. Thyroid ima
- C. Inferior thyroid vein
- D. Inferior thyroid artery (Correct Answer)
Explanation: ***Inferior thyroid artery*** - The **inferior thyroid artery** is typically located deep and lateral to the trachea, arising from the thyrocervical trunk and approaching the thyroid gland posteriorly [1]. - During emergency tracheostomy, the incision is made in the midline over the 2nd-4th tracheal rings, whereas this artery runs laterally at a lower level (typically around the 6th tracheal ring). - Its **deep and lateral anatomical position** makes it the least vulnerable structure among the options during a standard midline tracheostomy incision [1]. *Isthmus of the thyroid* - The **isthmus of the thyroid gland** crosses the trachea anteriorly, typically overlying the 2nd, 3rd, and 4th tracheal rings. - It lies directly in the path of an emergency tracheostomy incision and is frequently encountered, often requiring division or retraction to access the trachea. - This structure is **highly likely to be damaged** during the procedure. *Thyroid ima artery* - The **thyroid ima artery** is an inconsistent vessel, present in approximately 3-10% of individuals, arising from the brachiocephalic trunk or aortic arch. - When present, it ascends in the **midline** to supply the inferior pole of the thyroid gland, placing it directly in the path of the tracheostomy incision. - This vessel is **highly susceptible to injury** when present, potentially causing significant arterial bleeding. *Inferior thyroid vein* - The **inferior thyroid veins** drain the thyroid gland and form a venous plexus anterior to the trachea, superficial to the thyroid isthmus [1]. - This plexus lies in the **superficial surgical field** and is prone to injury during the midline cervical incision for tracheostomy. - Damage to these veins commonly occurs and can lead to significant venous bleeding [1].
Question 7: A patient presents with a mediastinal mass and is diagnosed with pure red cell aplasia. What is the most probable underlying cause?
- A. Bronchogenic carcinoma
- B. T-cell Acute Lymphoblastic Leukemia
- C. Non-Hodgkin Lymphoma
- D. Thymic neoplasia (Correct Answer)
Explanation: ***Thymic neoplasia*** - **Thymoma** is strongly associated with **pure red cell aplasia (PRCA)**, where the body's immune system, influenced by the abnormal thymus, attacks and destroys red blood cell precursors in the bone marrow. - A mediastinal mass, particularly in an adult presenting with PRCA, should raise strong suspicion for a **thymic tumor**. *Bronchogenic carcinoma* - While bronchogenic carcinoma can present as a **mediastinal mass**, it is not typically associated with **pure red cell aplasia**. - Its paraneoplastic syndromes usually involve endocrine or neurological manifestations rather than direct hematopoietic suppression of red cell precursors. *T-cell Acute Lymphoblastic Leukemia* - **T-cell ALL** can present with a **mediastinal mass** due to thymic involvement, but it causes **pancytopenia** or **anemia** due to bone marrow infiltration by leukemic cells, not a selective aplasia of red cell precursors. - In T-cell ALL, there would be a proliferation of immature lymphoid cells, differentiating it from PRCA. *Non-Hodgkin Lymphoma* - Certain types of **non-Hodgkin lymphoma** (e.g., lymphoblastic lymphoma) can present with a **mediastinal mass**. - However, lymphoma would typically cause **bone marrow infiltration** leading to cytopenias, not specifically **pure red cell aplasia**, where only erythroid precursors are targeted.
Question 8: Which of the following is not seen in the anterior mediastinum?
- A. Thyroid tumor
- B. Neurogenic tumor (Correct Answer)
- C. Lymphoma
- D. Thymoma
Explanation: ***Neurogenic tumor*** - **Neurogenic tumors** typically arise from nerve tissue and are most commonly found in the **posterior mediastinum**. - The posterior mediastinum is the primary location for these tumors due to the presence of the **sympathetic chain**, intercostal nerves, and vagus nerve. *Thyroid tumour* - **Ectopic thyroid tissue** can be found in the anterior mediastinum, and this tissue can give rise to thyroid tumors [1]. - While less common than in the neck, substernal or **ectopic thyroid goiters** and carcinomas can present in this compartment [1]. *Thymoma* - The **thymus gland** is located in the anterior mediastinum, making thymoma (a tumor of the thymus) a classic anterior mediastinal mass [1]. - Thymomas are often associated with **paraneoplastic syndromes** like myasthenia gravis. *Lymphoma* - **Lymphatic tissue**, including lymph nodes, is plentiful in the anterior mediastinum [1]. - **Hodgkin's and non-Hodgkin's lymphoma** frequently present as masses in the anterior mediastinum, often causing symptoms due to compression of surrounding structures [1].
Question 9: NOT a content of superior mediastinum
- A. Arch of aorta
- B. Thymus
- C. Pulmonary trunk
- D. Left superior intercostal artery (Correct Answer)
Explanation: ***Left superior intercostal artery*** - The **left superior intercostal artery** arises from the **costocervical trunk** (a branch of the subclavian artery) and is NOT considered a primary content of the superior mediastinum. - It descends to supply the **first and second (sometimes third) intercostal spaces** on the left side. - While it may pass near the superior mediastinum, it is anatomically classified with the **posterior mediastinum** structures. *Arch of aorta* - The **arch of the aorta** is a major structure within the **superior mediastinum** [1]. - It gives off three major branches: brachiocephalic trunk, left common carotid artery, and left subclavian artery [2]. - It extends from approximately the level of the **second costal cartilage** to the **lower border of T4 vertebra**. *Thymus* - The **thymus gland** is located in the **anterior mediastinum**, NOT the superior mediastinum [1]. - It lies posterior to the sternum and anterior to the pericardium and great vessels. - However, it may extend superiorly into the lower part of the neck, and in some classifications, its superior portion overlaps with the superior mediastinum [1]. *Pulmonary trunk* - The **pulmonary trunk** is located in the **middle mediastinum** within the pericardial sac, NOT the superior mediastinum [1]. - It originates from the **right ventricle** at a level below the superior mediastinum (which extends only to the sternal angle/T4-5 level). - It carries deoxygenated blood from the right ventricle to the lungs.
Question 10: Which structures are located anterior to the transverse sinus?
- A. Right atrium
- B. Left atrium
- C. Right pulmonary artery
- D. Aorta (Correct Answer)
Explanation: ***Aorta*** - The **transverse sinus of the pericardium** is a passage within the pericardial cavity that separates the great arteries (aorta and pulmonary trunk) anteriorly from the atria and great veins posteriorly. - The **ascending aorta** and **pulmonary trunk** are both located anterior to the transverse sinus. - This anatomical relationship is clinically important during cardiac surgery, as the transverse sinus can be used to pass ligatures around the great vessels. *Right atrium* - The **right atrium** is located posterior to the transverse sinus. - It forms part of the posterior wall of the pericardial cavity and receives the superior and inferior venae cavae. - The transverse sinus separates the atria from the anteriorly positioned great arteries. *Left atrium* - The **left atrium** is also positioned posterior to the transverse sinus. - It forms the base of the heart and receives the pulmonary veins. - Like the right atrium, it lies behind the plane of the transverse sinus. *Right pulmonary artery* - The **right pulmonary artery** is a branch of the pulmonary trunk that passes to the right lung. - While the **pulmonary trunk** itself is anterior to the transverse sinus, the **right pulmonary artery** branch courses laterally and posteriorly, passing behind the ascending aorta and superior vena cava. - Therefore, the right pulmonary artery is NOT considered anterior to the transverse sinus in the same way the main great vessels (aorta and pulmonary trunk) are.
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