Thoracic cross-sections US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Thoracic cross-sections. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Thoracic cross-sections US Medical PG Question 1: A 45-year-old male patient presents with difficulty swallowing and hoarseness that has progressively worsened over the past month. During physical examination, the physician notices that the patient's left vocal cord is paralyzed. The paralysis is most likely due to compression of which of the following nerves?
- A. Left superior laryngeal nerve
- B. Left vagus nerve
- C. Right recurrent laryngeal nerve
- D. Left recurrent laryngeal nerve (Correct Answer)
Thoracic cross-sections Explanation: ***Left recurrent laryngeal nerve***
- The **left recurrent laryngeal nerve** innervates all intrinsic muscles of the left larynx, except the cricothyroid muscle [1].
- Damage or compression of this nerve leads to **left vocal cord paralysis** and associated symptoms like hoarseness and difficulty swallowing (dysphagia).
*Left superior laryngeal nerve*
- The **superior laryngeal nerve** innervates the cricothyroid muscle, which is responsible for tensing the vocal cords.
- Damage to this nerve primarily affects **pitch control** and would not typically cause complete vocal cord paralysis.
*Left vagus nerve*
- The **vagus nerve** gives rise to both the superior and recurrent laryngeal nerves [1].
- While damage to the main vagus nerve would cause vocal cord paralysis, the more specific finding of isolated vocal cord paralysis points to an issue with its branch, the recurrent laryngeal nerve [1].
*Right recurrent laryngeal nerve*
- The **right recurrent laryngeal nerve** controls the intrinsic muscles of the right larynx.
- Damage to this nerve would result in **right vocal cord paralysis**, not left vocal cord paralysis as described in the patient.
Thoracic cross-sections US Medical PG Question 2: A 36-year-old man presents to the physician with difficulty in breathing for 3 hours. There is no history of chest pain, cough or palpitation. He is a chronic smoker and underwent elective cholecystectomy one month back. There is no history of chronic or recurrent cough, wheezing or breathlessness. His temperature is 38.2°C (100.8°F), pulse is 108/min, blood pressure is 124/80 mm Hg, and respirations are 25/min. His arterial oxygen saturation is 98% in room air as shown by pulse oximetry. After a detailed physical examination, the physician orders a plasma D-dimer level, which was elevated. A contrast-enhanced computed tomography (CT) of the chest shows a filling defect in a segmental pulmonary artery on the left side. Which of the following signs is most likely to have been observed by the physician during the physical examination of this patient’s chest?
- A. Pleural friction rub
- B. Bilateral wheezing
- C. Systolic murmur at the left sternal border
- D. Localized rales (Correct Answer)
- E. S3 gallop
Thoracic cross-sections Explanation: ***Localized rales***
- The patient's presentation with **sudden onset dyspnea**, risk factors (recent surgery, smoking), elevated D-dimer, and a CT scan showing a filling defect in the pulmonary artery strongly points to a **pulmonary embolism (PE)**.
- While PE often presents with normal lung auscultation, localized rales or crackles can be heard if there is an associated **pulmonary infarction** or local inflammation.
*Pleural friction rub*
- A **pleural friction rub** indicates inflammation of the pleura, which can occur in PE if the infarct involves the pleural surface.
- However, it is a less common finding than localized rales and is more characteristic of conditions like pleurisy or pneumonia.
*Bilateral wheezing*
- **Bilateral wheezing** is typically associated with diffuse airway obstruction, as seen in asthma or chronic obstructive pulmonary disease (COPD).
- This patient has no history of chronic respiratory conditions and the presentation is acute dyspnea, making diffuse airway obstruction less likely.
*Systolic murmur at the left sternal border*
- A **systolic murmur at the left sternal border** can be indicative of tricuspid regurgitation, often seen in the setting of **pulmonary hypertension** and right heart strain associated with a massive PE.
- However, with a stable blood pressure and moderate heart rate, severe right heart strain leading to a murmur is less likely in this scenario of a segmental PE.
*S3 gallop*
- An **S3 gallop** is a low-pitched sound heard during early diastole, often indicating **volume overload** or **ventricular dysfunction**.
- In the context of PE, an S3 often suggests significant **right ventricular dysfunction** due to acute pressure overload; this is more common with large or massive PEs causing hemodynamic instability, which is not indicated here.
Thoracic cross-sections US Medical PG Question 3: A 69-year-old smoker presents to physician after noticing that his face seems to be more swollen than usual. Upon further questioning, he reports increasing shortness of breath and cough over the past 6 months. On exam, his physician notices venous distention in his neck and distended veins in the upper chest and arms. Chest radiograph shows a right upper lobe mass. What is the embryologic origin of the vessel being compressed by this patient's tumor?
- A. Cardinal veins (Correct Answer)
- B. Primitive ventricle
- C. Left horn of sinus venosus
- D. Truncus arteriosus
- E. Bulbus cordis
Thoracic cross-sections Explanation: ***Cardinal veins***
- The symptoms of facial swelling, neck vein distention, and upper chest/arm vein distention, especially with a right upper lobe mass, are classic for **superior vena cava (SVC) syndrome**.
- The **SVC** is formed from the fusion of the anterior **cardinal veins**, which drain the upper body during embryonic development.
*Primitive ventricle*
- The **primitive ventricle** develops into parts of the left and right **ventricles** of the heart.
- It is not directly involved in the formation of major systemic veins like the SVC.
*Left horn of sinus venosus*
- The **left horn of the sinus venosus** mostly regresses and contributes to structures like the **coronary sinus** and the oblique vein of the left atrium.
- It does not form the SVC, which drains the upper body.
*Truncus arteriosus*
- The **truncus arteriosus** is an embryonic structure that separates to form the **aorta** and the **pulmonary artery**.
- It is an arterial structure, not a venous structure that would be compressed in SVC syndrome.
*Bulbus cordis*
- The **bulbus cordis** develops into the **conus arteriosus** (infundibulum) of the right ventricle and the **aortic vestibule** of the left ventricle.
- Like the truncus arteriosus, it is involved in arterial outflow tracts and not the formation of the SVC.
Thoracic cross-sections US Medical PG Question 4: A 38-year-old woman undergoes hemithyroidectomy for treatment of localized, well-differentiated papillary thyroid carcinoma. The lesion is removed with clear margins. However, during the surgery, a structure lying directly adjacent to the superior thyroid artery at the upper pole of the thyroid lobe is damaged. This patient is most likely to experience which of the following symptoms?
- A. Shortness of breath
- B. Weakness of shoulder shrug
- C. Voice pitch limitation (Correct Answer)
- D. Difficulty swallowing
- E. Ineffective cough
Thoracic cross-sections Explanation: ***Voice pitch limitation***
- Damage to the structure directly adjacent to the **superior thyroid artery** at the upper pole of the thyroid likely involves the **external branch of the superior laryngeal nerve (EBSLN)**.
- This nerve innervates the **cricothyroid muscle**, which is responsible for **tensing the vocal cords** and controlling **voice pitch**.
- Injury results in inability to change pitch, voice fatigue during prolonged speaking, and reduced vocal range.
*Shortness of breath*
- While damage to other nerves like the **recurrent laryngeal nerve** could cause vocal cord paralysis and potentially lead to airway compromise, this is less directly associated with the superior thyroid artery.
- Shortness of breath is not the specific consequence of EBSLN injury near the superior thyroid artery.
*Weakness of shoulder shrug*
- Weakness of shoulder shrug is associated with damage to the **spinal accessory nerve (cranial nerve XI)**, which innervates the **trapezius muscle**.
- This nerve is anatomically distinct from structures near the superior thyroid artery at the upper pole of the thyroid.
*Difficulty swallowing*
- Difficulty swallowing (dysphagia) can result from damage to the **vagus nerve (cranial nerve X)** or its pharyngeal branches, but it is not the direct consequence of injury near the superior thyroid artery.
- Damage to the EBSLN primarily affects voice pitch and quality, not swallowing.
*Ineffective cough*
- An ineffective cough results from paralysis of the vocal cords (preventing glottic closure) or weakness of respiratory muscles, typically from **recurrent laryngeal nerve** damage or phrenic nerve injury.
- EBSLN damage primarily affects voice pitch and does not significantly impair cough effectiveness.
Thoracic cross-sections US Medical PG Question 5: A 55-year-old man is brought to the emergency department by his wife after falling down. About 90 minutes ago, they were standing in their kitchen making lunch and chatting when he suddenly complained that he could not see as well, felt weak, and was getting dizzy. He began to lean to 1 side, and he eventually fell to the ground. He did not hit his head. In the emergency department, he is swaying while seated, generally leaning to the right. The general physical exam is unremarkable. The neurologic exam is notable for horizontal nystagmus, 3/5 strength in the right arm, ataxia of the right arm, and absent pinprick sensation in the left arm and left leg. The computed tomography (CT) scan of the head is unremarkable. Which of the following is the most likely single location of this patient's central nervous system lesion?
- A. Primary motor cortex
- B. Thalamus
- C. Lateral medulla (Correct Answer)
- D. Primary somatosensory cortex
- E. Anterior spinal cord
Thoracic cross-sections Explanation: ***Lateral medulla***
- The combination of **ipsilateral ataxia** and **weakness** (right arm) along with **contralateral pain and temperature sensory loss** (left arm and leg) is classic for a **lateral medullary syndrome (Wallenberg syndrome)**.
- **Horizontal nystagmus**, vertigo, and leaning to one side are also consistent with involvement of vestibular nuclei and cerebellar pathways in the lateral medulla.
*Primary motor cortex*
- A lesion here would cause **contralateral weakness or paralysis** but would not explain the ipsilateral ataxia, nystagmus, or contralateral pain and temperature loss.
- Sensory deficits would be minimal or absent, and would primarily affect discriminative touch.
*Thalamus*
- A thalamic lesion could cause **contralateral sensory loss** (affecting all modalities) and potentially some motor deficits or ataxia, but it typically does not cause **ipsilateral ataxia** or **nystagmus** in the pattern described.
- The specific combination of ipsilateral motor and contralateral sensory deficits points away from a pure thalamic lesion.
*Primary somatosensory cortex*
- A lesion in this area would primarily result in **contralateral deficits in discriminative touch, proprioception, and stereognosis**, not pain and temperature sensation.
- It would not explain the motor deficits, ataxia, or nystagmus seen in the patient.
*Anterior spinal cord*
- Damage to the anterior spinal cord (e.g., **anterior spinal artery syndrome**) would cause **bilateral motor weakness (paraplegia/quadriplegia)** and **bilateral loss of pain and temperature sensation** below the level of the lesion.
- It would not account for the nystagmus, vertigo, or the specific combination of ipsilateral and contralateral deficits observed in this patient, which are characteristic of brainstem involvement.
Thoracic cross-sections US Medical PG Question 6: A 23-year-old man is brought to the emergency department by a coworker for an injury sustained at work. He works in construction and accidentally shot himself in the chest with a nail gun. Physical examination shows a bleeding wound in the left hemithorax at the level of the 4th intercostal space at the midclavicular line. Which of the following structures is most likely injured in this patient?
- A. Right atrium of the heart
- B. Inferior vena cava
- C. Left upper lobe of the lung (Correct Answer)
- D. Left atrium of the heart
- E. Superior vena cava
Thoracic cross-sections Explanation: ***Left upper lobe of the lung***
- The **left upper lobe of the lung** extends to the 4th intercostal space at the midclavicular line, making it the most probable structure to be traversed by a penetrating injury at this location.
- The **pleural cavity** and lung tissue are superficially located in this region, making them highly susceptible to injury from a nail gun.
*Right atrium of the heart*
- The **right atrium** is located predominantly on the right side of the sternum, more centrally, and slightly to the right of the midclavicular line.
- An injury at the **left 4th intercostal space at the midclavicular line** would typically be too lateral and superior to directly injure the right atrium.
*Inferior vena cava*
- The **inferior vena cava (IVC)** enters the right atrium from below, primarily located within the abdomen and passing through the diaphragm at the level of T8.
- Its position is far too **inferior and posterior** relative to the 4th intercostal space to be directly injured by this wound.
*Left atrium of the heart*
- The **left atrium** is the most posterior chamber of the heart and is largely covered by the left ventricle.
- Although part of the heart is on the left, an injury at the **4th intercostal space, midclavicular line**, would likely impact the left ventricle or lung tissue before reaching the left atrium, which is located more posteriorly and medially.
*Superior vena cava*
- The **superior vena cava (SVC)** is located to the right of the midline, formed by the brachiocephalic veins behind the right first costal cartilage.
- Its position is too **medial and superior**, on the right side, to be directly injured by a nail penetrating the left 4th intercostal space at the midclavicular line.
Thoracic cross-sections US Medical PG Question 7: A 40-year-old woman is brought to the emergency department by a paramedic team from the scene of a motor vehicle accident where she was the driver. The patient was restrained by a seat belt and was unconscious at the scene. On physical examination, the patient appears to have multiple injuries involving the trunk and extremities. There are no penetrating injuries to the chest. As part of her trauma workup, a CT scan of the chest is ordered. At what vertebral level of the thorax is this image from?
- A. T1
- B. T6
- C. T4
- D. T5
- E. T8 (Correct Answer)
Thoracic cross-sections Explanation: ***T8***
- The CT image shows the **inferior vena cava (IVC)** located anterior and to the right of the aorta, and the **esophagus** located posterior to the aorta and slightly to the left. The **azygos vein** is seen to the right of the vertebral body and posterior to the esophagus.
- The **mainstem bronchi** are no longer visible, indicating a level below the carina. The presence of the IVC, aorta, esophagus, and azygos vein with the absence of mainstem bronchi is characteristic of the **T8 vertebral level**.
*T1*
- At the T1 level, the structures would primarily be the **trachea** anterior to the esophagus, with the main great vessels (e.g., brachiocephalic veins and arteries) visible, not the IVC.
- The mainstem bronchi would not yet be visualized at this higher level.
*T6*
- At the T6 level, the **trachea would have already bifurcated into the mainstem bronchi**, which would be prominent structures visible on the CT scan.
- While the aorta and esophagus would be present, the specific arrangement relative to the mainstem bronchi would differentiate it from T8.
*T4*
- The T4 level is typically associated with the **carina**, where the trachea bifurcates into the mainstem bronchi.
- The great vessels would be prominent, but the IVC in its more inferior course would not be as distinctly visualized in this configuration compared to T8.
*T5*
- At the T5 level, the **mainstem bronchi** would still be clearly visible, having just diverged from the trachea.
- While vessels like the aorta are present, the key differentiating factor from T8 is the presence of the mainstem bronchi.
Thoracic cross-sections US Medical PG Question 8: An otherwise healthy 58-year-old man comes to the physician because of a 1-year history of episodic coughing whenever he cleans his left ear. There is no history of hearing loss, tinnitus, or vertigo. Stimulating his left ear canal with a cotton swab triggers a bout of coughing. The physician informs him that these symptoms are caused by hypersensitivity of a cranial nerve. A peripheral lesion of this nerve is most likely to manifest with which of the following findings on physical examination?
- A. Ipsilateral sensorineural hearing loss
- B. Ipsilateral deviation of the tongue
- C. Inability to raise ipsilateral eyebrow
- D. Decreased secretion from ipsilateral sublingual gland
- E. Ipsilateral vocal cord palsy (Correct Answer)
Thoracic cross-sections Explanation: ***Ipsilateral vocal cord palsy***
- The sensation in the external auditory canal that triggers a cough reflex is mediated by the **auricular branch of the vagus nerve (CN X)**, also known as Arnold's nerve.
- A peripheral lesion of the vagus nerve would most likely affect its motor functions, including the innervation of the **larynx**, leading to **ipsilateral vocal cord palsy** and hoarseness.
*Ipsilateral sensorineural hearing loss*
- Hearing loss is primarily associated with pathology of the **vestibulocochlear nerve (CN VIII)**, not the vagus nerve.
- The patient's presentation does not describe any auditory symptoms.
*Ipsilateral deviation of the tongue*
- Tongue deviation is a sign of compromise of the **hypoglossal nerve (CN XII)**, which controls the intrinsic and extrinsic muscles of the tongue.
- This is not a function of the vagus nerve.
*Inability to raise ipsilateral eyebrow*
- The ability to raise the eyebrow is controlled by the **facial nerve (CN VII)**, which innervates the muscles of facial expression.
- Vagus nerve lesions do not typically present with facial weakness.
*Decreased secretion from ipsilateral sublingual gland*
- Secretion from the sublingual gland is controlled by the **facial nerve (CN VII)** via the submandibular ganglion.
- While the vagus nerve has autonomic functions, it does not directly control sublingual gland secretion.
Thoracic cross-sections US Medical PG Question 9: A 55-year-old man visits the clinic with his wife. He has had difficulty swallowing solid foods for the past 2 months. His wife adds that his voice is getting hoarse but they thought it was due to his recent flu. His medical history is significant for type 2 diabetes mellitus for which he is on metformin. He suffered from many childhood diseases due to lack of medical care and poverty. His blood pressure is 125/87 mm Hg, pulse 95/min, respiratory rate 14/min, and temperature 37.1°C (98.7°F). On examination, an opening snap is heard over the cardiac apex. An echocardiogram shows an enlarged cardiac chamber pressing into his esophagus. Changes in which of the following structures is most likely responsible for this patient’s symptoms?
- A. Patent ductus arteriosus
- B. Right ventricle
- C. Left ventricle
- D. Left atrium (Correct Answer)
- E. Right atrium
Thoracic cross-sections Explanation: ***Left atrium***
- The patient's symptoms of **dysphagia (difficulty swallowing)** and **hoarseness** suggest compression of anatomical structures by an enlarged cardiac chamber, which the echocardiogram confirms.
- An enlarged **left atrium**, typically due to **mitral stenosis**, can compress the esophagus (leading to dysphagia) and the **recurrent laryngeal nerve** (leading to hoarseness, known as Ortner's syndrome). The **opening snap** at the apex is also highly characteristic of mitral stenosis.
*Patent ductus arteriosus*
- A **patent ductus arteriosus (PDA)** is a congenital heart defect that typically causes a **continuous murmur** and may lead to pulmonary hypertension or heart failure, but not direct compression of the esophagus or recurrent laryngeal nerve.
- The symptoms of PDA are usually present earlier in life, though uncorrected large PDAs can cause symptoms in adulthood, they do not cause dysphagia or hoarseness through direct esophageal compression.
*Right ventricle*
- An enlarged **right ventricle** usually causes symptoms related to right heart failure like **peripheral edema** or **dyspnea** due to pulmonary hypertension.
- It is not anatomically positioned to compress the esophagus or recurrent laryngeal nerve in a way that would cause dysphagia or hoarseness.
*Left ventricle*
- An enlarged **left ventricle** (e.g., due to hypertension or aortic stenosis) primarily causes symptoms like **dyspnea on exertion** or **angina**.
- While a severely dilated left ventricle can displace other structures, it does not typically cause direct esophageal compression leading to dysphagia or recurrent laryngeal nerve compression leading to hoarseness.
*Right atrium*
- An enlarged **right atrium** might be seen in conditions like tricuspid regurgitation or right heart failure but can manifest as **edema** or **jugular venous distention**.
- It is not anatomically positioned to cause dysphagia or hoarseness from esophageal or recurrent laryngeal nerve compression.
Thoracic cross-sections US Medical PG Question 10: A previously healthy 20-year-old man comes to the physician because of a 6-month history of a painless mass in his left groin that has been gradually increasing in size. Physical examination shows a 3x3-cm oval, non-tender left inguinal mass and a fluctuant, painless left scrotal swelling that increase in size with coughing. Which of the following is the most likely cause of this patient's symptoms?
- A. Weakening of transversalis fascia
- B. Widening of femoral ring
- C. Reduced fluid reabsorption at tunica vaginalis
- D. Failure of processus vaginalis to close (Correct Answer)
- E. Obstruction of left spermatic vein
Thoracic cross-sections Explanation: ***Failure of processus vaginalis to close***
- The combination of a left inguinal mass and a scrotal swelling that both **increase in size with coughing** (suggesting **reducibility** and a connection to the abdominal cavity) in a young man points towards an **indirect inguinal hernia**.
- Indirect inguinal hernias occur due to the **persistence of the processus vaginalis**, which normally obliterates, allowing abdominal contents to herniate through the **deep inguinal ring** into the inguinal canal and potentially the scrotum.
*Weakening of transversalis fascia*
- This typically leads to a **direct inguinal hernia**, where abdominal contents protrude directly through the **posterior wall of the inguinal canal** through **Hesselbach's triangle**, medial to the inferior epigastric vessels.
- While it can cause an inguinal mass, it is less common to have an associated scrotal swelling that increases with coughing in the same manner as an indirect hernia, especially in a young, previously healthy individual without risk factors for fascial weakening.
*Widening of femoral ring*
- Widening of the femoral ring is the underlying cause of a **femoral hernia**.
- Femoral hernias typically present as a mass **below the inguinal ligament** and medial to the femoral vein, and are more common in women due to a wider pelvis.
*Reduced fluid reabsorption at tunica vaginalis*
- This pathology results in a **hydrocele**, which is an accumulation of fluid within the **tunica vaginalis**.
- While it presents as a **painless scrotal swelling**, a hydrocele typically does not involve an inguinal mass, nor does it increase in size with coughing (unless it's a **communicating hydrocele**, which means the processus vaginalis is still patent, essentially linking it back to the correct answer).
*Obstruction of left spermatic vein*
- Obstruction of the left spermatic vein usually leads to a **varicocele**, which is a dilation of the **pampiniform venous plexus**.
- A varicocele typically presents as a "bag of worms" sensation in the scrotum, often on the left side, and usually **decreases in size when lying down**, which is different from the symptoms described.
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