Anatomical Aspects of Infections — MCQs
Most common route of nosocomial infection [Hospital-acquired infection]?
Which of the following viruses is not spread by the fecal-oral route?
Biopsy of the exposed surface of the palatine tonsil reveals which type of tissue?
Trismus is commonly seen in
All are true about amoebic liver abscess except?
Kanavel's sign is diagnosed in
38 year old male underwent a tooth extraction at a local dental camp. After few days he develops fever and trismus. On local examination, there is a swelling at the angle of jaw . He has a poor oral hygiene and tonsils were pushed medially .No membranous covering or discharging sinus were seen around tonsils. Most likely diagnosis in this condition would be ?
Trismus in parapharyngeal abscess is due to spasm of:
Which of the nerves shown in yellow color is not a part of the triangle of pain?
What type of joint is involved in looking to the right and left?
Anatomical Aspects of Infections Indian Medical PG Practice Questions and MCQs
Question 1: Most common route of nosocomial infection [Hospital-acquired infection]?
- A. Droplet transmission
- B. Direct contact (Correct Answer)
- C. Indirect contact
- D. Vehicle transmission
Explanation: **Direct contact** - **Direct contact** with colonized or infected patients is the predominant mode of transmission for many common nosocomial pathogens like **MRSA** and **VRE**. - This often involves healthcare workers' hands becoming contaminated and then touching other patients. *Droplet transmission* - Involves the transmission of infectious agents through **respiratory droplets** produced during coughing, sneezing, or talking. - While significant for some infections (e.g., influenza, pertussis), it is not the most common route overall for nosocomial infections. *Indirect contact* - Occurs when an infectious agent is transferred via a **contaminated intermediate object** or person. - Although important (e.g., contaminated medical devices), it is generally less frequent than direct patient-to-patient transmission. *Vehicle transmission* - Involves transmission through **contaminated inanimate vehicles** like food, water, medications, or surgical instruments. - While outbreaks can occur via this route (e.g., contaminated endoscopes), it is not the most common day-to-day transmission mechanism in hospitals.
Question 2: Which of the following viruses is not spread by the fecal-oral route?
- A. Rotavirus
- B. Hepatitis B virus (HBV) (Correct Answer)
- C. Hepatitis E virus (HEV)
- D. Norwalk virus (Norovirus)
Explanation: ***Hepatitis B virus (HBV)*** - HBV is primarily transmitted through **percutaneous** or **mucosal exposure** to infectious blood or body fluids, such as during sex, sharing needles, or from mother to child. - It is not typically spread via the **fecal-oral route**. *Hepatitis E virus (HEV)* - HEV is a common cause of **acute viral hepatitis** and is predominantly transmitted through the **fecal-oral route**, often via contaminated drinking water. - High viral loads are shed in the feces of infected individuals, leading to environmental contamination. *Rotavirus* - Rotavirus is a major cause of **severe diarrheal disease** in infants and young children, and its transmission occurs almost exclusively through the **fecal-oral route**. - The virus is highly stable in the environment and can spread rapidly in settings with poor hygiene. *Norwalk virus (Norovirus)* - Norovirus is a highly contagious virus that causes **gastroenteritis** and is notorious for outbreaks in crowded settings; its primary mode of transmission is the **fecal-oral route**. - It can also spread through contaminated food and water, or direct contact with infected individuals.
Question 3: Biopsy of the exposed surface of the palatine tonsil reveals which type of tissue?
- A. Stratified squamous epithelium (Correct Answer)
- B. Simple squamous epithelium
- C. Simple columnar epithelium
- D. Pseudostratified columnar ciliated epithelium
Explanation: The palatine tonsils are part of the **oropharynx**, which is subjected to mechanical abrasion from food and drink. **Stratified squamous epithelium** provides robust protection against such friction and is characteristic of surfaces needing high wear resistance. *Simple squamous epithelium* - This type of epithelium is found in areas where **diffusion** or **filtration** is important, such as the lining of blood vessels (endothelium) and alveoli of the lungs. - It would not provide adequate protection for the exposed surface of the tonsil that is subject to frequent mechanical stress. *Simple columnar epithelium* - Characterized by cells taller than they are wide, often found in the **gastrointestinal tract** for absorption and secretion. - It lacks the multi-layered structure needed for protection against the abrasive forces typical in the oropharynx. *Pseudostratified columnar ciliated epithelium* - This epithelium is primarily found in the **respiratory tract**, where its cilia help move mucus and trapped particles. - While it offers some protection, its primary function is not mechanical resistance, and it is not found on the exposed surfaces of the palatine tonsils.
Question 4: Trismus is commonly seen in
- A. Ludwig's angina
- B. Parapharyngeal abscess
- C. Retropharyngeal abscess
- D. Quinsy (Correct Answer)
Explanation: ***Quinsy*** - **Quinsy (peritonsillar abscess)** is the **most common cause of trismus** among pharyngeal infections. - Trismus occurs due to **inflammation and reflex spasm of the pterygoid muscles** adjacent to the abscess. - The severe pain and swelling in the peritonsillar region directly limit **mandibular movement**, making it difficult or impossible to open the mouth. - **Trismus is one of the cardinal clinical features** of quinsy. *Parapharyngeal abscess* - A **parapharyngeal abscess** can also cause trismus due to direct inflammation and irritation of the muscles of mastication. - However, it is **less common than quinsy** and typically presents with other prominent symptoms like **neck swelling**, lateral pharyngeal bulging, and internal carotid artery involvement risk. *Ludwig's angina* - While Ludwig's angina is a severe infection of the **submandibular and sublingual spaces**, trismus is **less common** and less pronounced compared to peritonsillar abscess. - The primary concern in Ludwig's angina is **airway obstruction** due to tongue elevation and "bull neck" swelling, not typically severe trismus. *Retropharyngeal abscess* - A **retropharyngeal abscess** is located behind the pharynx and typically manifests with **dysphagia**, **odynophagia**, **neck stiffness**, and respiratory distress. - While indirect muscle spasm can occur, **trismus is not a characteristic or common symptom** of retropharyngeal abscess, which primarily affects swallowing and neck mobility.
Question 5: All are true about amoebic liver abscess except?
- A. Multifocal abscess cannot be treated by aspiration
- B. More common in left side (Correct Answer)
- C. More common in female
- D. Metronidazole is mainstay of treatment
Explanation: Amoebic liver abscesses are much more common in the right lobe of the liver (>80-90%) due to the portal venous flow from the colon predominantly going to the right lobe [1]. The left lobe is rarely affected, and multifocal abscesses are also less common than a single right-sided lesion. Metronidazole is indeed the drug of choice for treating amoebic liver abscesses due to its excellent tissue penetration and efficacy against Entamoeba histolytica. Treatment for 7-10 days typically eradicates the trophozoites in the abscess and in the intestinal tract. While single, large abscesses often benefit from aspiration, multifocal abscesses are generally not amenable to aspiration due to their diffuse nature and numerous locations. Medical treatment with metronidazole is the primary approach for multifocal amoebic liver abscesses. Amoebic liver abscesses are actually more common in males than females, with a male-to-female ratio typically ranging from 7:1 to 10:1. This predisposition in males is not fully understood but may be related to hormonal factors or lifestyle differences.
Question 6: Kanavel's sign is diagnosed in
- A. Acute paronychia
- B. Flexor tendon sheath infection (Correct Answer)
- C. Web space infection
- D. Mid palmar infection
Explanation: ***Flexor tendon sheath infection*** - **Kanavel's signs** are a classic set of four criteria used to diagnose **flexor tenosynovitis**, which is an infection of the flexor tendon sheath. - The four signs are **uniform swelling** of the digit, **flexed posture** of the digit, **tenderness along the course of the flexor sheath**, and **pain on passive extension** of the digit. *Acute paronychia* - This is an **infection of the nail fold**, typically presenting with localized redness, swelling, and pain around the nail. - It does not involve the flexor tendon sheath and therefore does not exhibit Kanavel's signs. *Web space infection* - A web space infection, also known as a **collar button abscess**, occurs in the subcutaneous tissue of the interdigital space. - While painful, it presents with swelling between the digits and does not involve the flexor tendon sheath. *Mid palmar infection* - This refers to an infection in the **mid palmar space**, a deep fascial space in the palm of the hand. - It would present with diffuse palmar swelling and tenderness but would not typically involve the specific signs related to flexor tendon sheath inflammation.
Question 7: 38 year old male underwent a tooth extraction at a local dental camp. After few days he develops fever and trismus. On local examination, there is a swelling at the angle of jaw . He has a poor oral hygiene and tonsils were pushed medially .No membranous covering or discharging sinus were seen around tonsils. Most likely diagnosis in this condition would be ?
- A. Ludwig's angina
- B. Parapharyngeal abscess (Correct Answer)
- C. Retropharyngeal abscess
- D. Peritonsillar abscess
Explanation: ***Parapharyngeal abscess*** - The patient's history of a recent **tooth extraction** and poor oral hygiene, followed by fever, trismus, swelling at the angle of the jaw, and medially pushed tonsils, are classic symptoms of a **parapharyngeal abscess**. - This type of abscess develops in the **deep neck spaces** and can be caused by odontogenic infections, leading to significant swelling and potential airway compromise. *Ludwig's angina* - While also an odontogenic infection, **Ludwig's angina** primarily affects the **submandibular, sublingual, and submental spaces**, characterized by firm, brawny induration of the floor of the mouth and neck, with less prominent swelling at the angle of the jaw and often **tongue elevation**. - It does not typically present with the tonsils being pushed medially, as it involves spaces anterior to the tonsillar region. *Retropharyngeal abscess* - A **retropharyngeal abscess** typically presents with severe **dysphagia**, odynophagia, fever, and neck stiffness, often resulting from upper respiratory tract infections or trauma. - The swelling would be more prominent in the posterior pharyngeal wall, and would less commonly cause significant swelling at the angle of the jaw or trismus unless extensive. *Peritonsillar abscess* - A **peritonsillar abscess** usually develops due to a complication of tonsillitis, presenting with severe **sore throat**, unilateral tonsillar swelling, and a characteristic deviation of the **uvula** to the opposite side. - While tonsils are affected, they are not typically pushed *medially* from an external deep neck space infection in this manner, and swelling at the angle of the jaw is less pronounced.
Question 8: Trismus in parapharyngeal abscess is due to spasm of:
- A. Medial pterygoid (Correct Answer)
- B. Temporalis
- C. Masseter muscle
- D. Lateral pterygoid
Explanation: ***Medial pterygoid*** - The **medial pterygoid muscle** is intimately associated with the parapharyngeal space, and inflammation or infection (abscess) in this region directly irritates it. - **Spasm** of the medial pterygoid muscle, a primary muscle of mastication involved in jaw closure, is the direct cause of **trismus** (difficulty opening the mouth) in parapharyngeal abscess. *Masseter muscle* - While the **masseter** is a strong muscle of mastication and contributes to jaw closure, it is located more superficially and is less directly affected by an abscess in the parapharyngeal space. - Its involvement in trismus due to parapharyngeal abscess is typically secondary, arising from generalized muscle guarding rather than direct irritation. *Lateral pterygoid* - The **lateral pterygoid muscle** is primarily involved in jaw opening (depression) and protrusion. - Spasm of this muscle would typically lead to difficulty closing the jaw or deviations, rather than the profound difficulty in opening characteristic of trismus. *Temporalis* - The **temporalis muscle** is a major muscle for jaw elevation and retraction, contributing significantly to biting force. - While temporalis spasm can cause trismus, it is less directly impacted by a parapharyngeal abscess compared to the medial pterygoid muscle.
Question 9: Which of the nerves shown in yellow color is not a part of the triangle of pain?
- A. Lateral femoral cutaneous nerve
- B. Femoral branch of Genitofemoral nerve
- C. Genital branch of Genitofemoral nerve
- D. Femoral nerve (Correct Answer)
Explanation: ***Femoral nerve*** The **femoral nerve** is located laterally to the **femoral artery** and typically runs within the **iliopsoas groove**, outside the boundaries of the **triangle of pain**. Its position is more posterior and lateral, making it less vulnerable to injury during inguinal hernia repair compared to the nerves that traverse the "triangle of pain". *Lateral femoral cutaneous nerve* The **lateral femoral cutaneous nerve** is consistently found within the boundaries of the **triangle of pain**, increasing its susceptibility to injury during Lichtenstein hernia repair. Damage to this nerve can lead to **meralgia paraesthetica**, characterized by burning pain and numbness in the lateral thigh. *Femoral branch of Genitofemoral nerve* The **femoral branch of the genitofemoral nerve** typically crosses the **deep inguinal ring** and lies within the lateral part of the **triangle of pain**. Injury to this nerve during hernia repair can result in numbness or altered sensation in the anterior thigh. *Genital branch of Genitofemoral nerve* The **genital branch of the genitofemoral nerve** is located within the medial and inferior aspects of the **triangle of pain**. Damage to this nerve most commonly causes numbness or pain in the scrotum/labia majora and medial thigh.
Question 10: What type of joint is involved in looking to the right and left?
- A. Ellipsoid joint
- B. Pivot joint (Correct Answer)
- C. Saddle joint
- D. Hinge joint
Explanation: The movement of looking to the right and left (rotation of the head) occurs primarily at the **atlanto-axial joint** (between the C1 atlas and C2 axis). This is a classic example of a **pivot (trochoid) joint**. Specifically, the dens (odontoid process) of the axis acts as a pivot point, held against the anterior arch of the atlas by the transverse ligament, allowing for approximately 50% of total cervical rotation. **Analysis of Options:** * **Pivot joint (Correct):** Characterized by a central bony pivot surrounded by an osteoligamentous ring, allowing rotation around a single longitudinal axis. * **Ellipsoid joint (Incorrect):** The **atlanto-occipital joint** is an ellipsoid joint. It allows for "nodding" (flexion/extension) or the "Yes" movement, but not the "No" rotation. * **Saddle joint (Incorrect):** Examples include the first carpometacarpal joint. It allows movement in two planes but does not permit the pure rotation required for turning the head. * **Hinge joint (Incorrect):** Examples include the elbow or interphalangeal joints. These allow movement in only one plane (flexion/extension), similar to a door hinge. **High-Yield Clinical Pearls for NEET-PG:** * **The "No" Joint:** The atlanto-axial joint is often nicknamed the "No" joint. * **Crucial Ligament:** The **transverse ligament of the atlas** is the most important structure stabilizing this joint. Its rupture (e.g., in Rheumatoid Arthritis or Down Syndrome) can lead to atlanto-axial subluxation and spinal cord compression. * **Hangman’s Fracture:** This involves a fracture through the pars interarticularis of C2, often resulting from hyperextension of the neck.
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