Explosion Injuries — MCQs
During autopsy of a 65-year-old man who collapsed while eating dinner at home, a foreign body (food bolus) is found obstructing the larynx with no other injuries. The manner of death is:
In blast injury, which organ is most likely to be damaged first?
Which one of the following is a secondary brain injury?
In a blast injury, which of the following organs is least involved?
In air blast injury, which is the most commonly affected organ? CMC (Vellore) 07; AI 09; AIIMS 10; NEET 14
The image shows:
Bone pearls or wax drippings are pathognomonic of which type of injury?
Arborescent marks or filigree burns are typically seen in which type of injury?
What is a 'brush burn'?
A 'black eye' is a type of:
Explosion Injuries Indian Medical PG Practice Questions and MCQs
Question 1: During autopsy of a 65-year-old man who collapsed while eating dinner at home, a foreign body (food bolus) is found obstructing the larynx with no other injuries. The manner of death is:
- A. Intentional harm
- B. Self-inflicted harm
- C. Unintentional injury (Correct Answer)
- D. Death from natural causes
Explanation: ***Unintentional injury*** - The presence of a **food bolus obstructing the respiratory tract** in a person who collapsed while eating, with **no evidence of trauma or suspicious circumstances**, is classified as **accidental/unintentional death**. - This is the most common manner of death associated with foreign body airway obstruction, particularly in elderly individuals or those with neurological conditions affecting swallowing. - **Café coronary syndrome** (choking on food mimicking cardiac arrest) is a classic example of accidental asphyxia. *Intentional harm (Homicide)* - Homicidal foreign body aspiration would require evidence of: - **Forced insertion** of the foreign body - **Other traumatic injuries** (bruising, struggle marks) - **Suspicious circumstances** at the scene - The scenario described lacks these features, making homicide unlikely. *Self-inflicted harm (Suicide)* - Suicide by foreign body aspiration is **extremely rare** and would require: - **Evidence of suicidal intent** (suicide note, psychiatric history) - Deliberate insertion beyond the gag reflex - Accidental choking while eating does not constitute suicidal behavior. *Death from natural causes* - **Natural death** results from disease processes, not external physical agents. - A foreign body causing mechanical airway obstruction is an **external cause of death**, not a natural disease process. - Even if the person had a predisposing medical condition, the immediate cause (foreign body obstruction) makes this an unintentional injury, not natural death.
Question 2: In blast injury, which organ is most likely to be damaged first?
- A. Tympanic membrane (Correct Answer)
- B. Liver
- C. Lung
- D. Gastrointestinal tract
Explanation: ***Tympanic membrane*** - The **tympanic membrane** is the most sensitive organ to the pressure waves generated by a blast, often rupturing even with relatively low blast overpressures. - Its thin, delicate structure and direct exposure to external air pressure make it highly vulnerable to barotrauma. *Gastrointestinal tract* - While the **gastrointestinal tract** can be damaged by blast waves, especially air-filled organs, this typically occurs after the tympanic membrane is affected. - Damage often includes hemorrhage, perforation, and mesenteric injury. *Liver* - The **liver** is a solid organ and is less susceptible to initial blast injury compared to air-filled structures. - Damage to the liver usually results from secondary mechanisms like blunt trauma from displacement or impact against other structures. *Lung* - **Blast lung** is a serious injury characterized by pulmonary contusions, hemorrhage, and edema, but it generally requires higher blast overpressure than tympanic membrane rupture. - The air-filled nature of the lungs makes them susceptible, but the tympanic membrane almost always fails first.
Question 3: Which one of the following is a secondary brain injury?
- A. Intracerebral haematoma with raised intracranial pressure (Correct Answer)
- B. Diffuse axonal injury
- C. Cortical lacerations
- D. Brainstem and hemispheric contusions
Explanation: ***Intracerebral haematoma with raised intracranial pressure*** - **Intracerebral haematoma** is a potentially treatable, secondary injury directly contributing to **raised intracranial pressure (ICP)**, leading to further brain damage if not managed. - **Secondary brain injuries** occur minutes to days after the initial impact, resulting from a cascade of events like ischaemia, oedema, and intracranial hypertension. *Diffuse axonal injury* - **Diffuse axonal injury (DAI)** is a **primary brain injury** caused by shearing forces at the moment of impact. - It is a direct consequence of the initial trauma, not a subsequent physiological process. *Cortical lacerations* - **Cortical lacerations** are **primary injuries**, representing a direct tearing or cutting of brain tissue due to the initial traumatic force. - These are immediately present at the time of injury and are not a consequence of subsequent physiological changes. *Brainstem and hemispheric contusions* - **Contusions** are localised areas of bruising on the brain, characteristic of a **primary brain injury**, occurring directly from the impact. - While contusions can evolve and contribute to secondary injury mechanisms like oedema, the contusion itself is a direct result of the initial trauma.
Question 4: In a blast injury, which of the following organs is least involved?
- A. GI tract
- B. Liver (Correct Answer)
- C. Eardrum
- D. Lungs
Explanation: ***Liver*** - Organ damage in blast injuries is largely dependent on the presence of **gas-containing organs** due to the direct effect of the pressure wave. The liver is a **solid organ** with high density and low gas content, making it relatively less susceptible to immediate primary blast injury compared to hollow, air-filled organs. - While significant blast forces can cause liver lacerations or hematomas through secondary or tertiary mechanisms (e.g., impact from projectiles or blunt trauma from being thrown), direct primary blast injury to the liver is **uncommon**. *GI tract* - The gastrointestinal tract is highly vulnerable to primary blast injury because it contains **gas**, especially the stomach and intestines. - The pressure wave causes significant barotrauma, leading to **perforations, hemorrhages, and pneumoperitoneum**. *Eardrum* - The eardrum (tympanic membrane) is the **most sensitive organ** to blast overpressure. - It readily ruptures even at relatively low blast magnitudes due to its **thin, delicate structure** and direct exposure to the pressure wave. *Lungs* - The lungs are highly susceptible to blast injury due to their **air-filled nature**, leading to classic "blast lung." - This can result in **pulmonary contusions, pneumothorax, hemothorax**, and severe respiratory distress.
Question 5: In air blast injury, which is the most commonly affected organ? CMC (Vellore) 07; AI 09; AIIMS 10; NEET 14
- A. Stomach
- B. Lungs
- C. Liver
- D. Eardrum (Correct Answer)
Explanation: ***Eardrum*** - The **eardrum (tympanic membrane)** is the most commonly affected organ in air blast injuries due to its thin, delicate structure and direct exposure to pressure waves. - Its rupture threshold is relatively low, making it highly susceptible to damage from sudden changes in air pressure. *Stomach* - While **hollow organs** like the stomach can be affected by blast injuries (secondary to barotrauma), they are less commonly ruptured than the eardrum. - Injury to the stomach generally requires a higher intensity blast or immersion in water. *Lungs* - **Pulmonary barotrauma** (blast lung) is a serious consequence of blast injury, characterized by hemorrhage, edema, and contusions. - However, the eardrum is far more frequently (and often mildly) injured compared to severe lung damage. *Liver* - The **liver**, being a solid organ, is generally more resistant to direct blast effects compared to hollow or air-filled structures. - Liver injuries from blast are more often due to secondary trauma (e.g., impact from flying debris) rather than the primary blast wave itself.
Question 6: The image shows:
- A. Chop wound
- B. Crush laceration
- C. Stab wound
- D. Split laceration (Correct Answer)
Explanation: ***Split laceration*** - **Split lacerations** result from **blunt force trauma** over a bony prominence, causing the skin to tear with irregular, jagged edges as seen in the image. - The wound shows typical features of tissue tearing rather than clean penetration, with **irregular margins** and evidence of stretching forces. *Stab wound* - **Stab wounds** are caused by **pointed objects** that penetrate cleanly, leaving relatively straight edges with minimal surrounding tissue damage. - The irregular, torn appearance in the image is inconsistent with the **clean, linear defect** typically seen in stab wounds. *Chop wound* - **Chop wounds** are produced by **heavy, sharp-edged instruments** like axes, combining features of incised wounds and lacerations with potential bone involvement. - This type would show a much **wider and deeper cut** with possible bone exposure, which is not evident in this case. *Crush laceration* - **Crush lacerations** occur from **compressive forces**, resulting in **stellate or irregular tears** with extensive soft tissue damage and surrounding bruising. - The wound lacks the **extensive tissue destruction**, **devitalized tissue**, and **significant bruising** characteristic of crush injuries.
Question 7: Bone pearls or wax drippings are pathognomonic of which type of injury?
- A. Burns
- B. Scalds
- C. Lightning strike
- D. Electrocution (Correct Answer)
Explanation: **Explanation:** **Correct Answer: D. Electrocution** The pathognomonic finding of **"Bone Pearls"** (also known as wax drippings or osteocytes) occurs specifically in high-voltage electrical injuries. When a high-tension current passes through the body, the bone—having the highest electrical resistance—generates intense heat (Joule’s effect). This heat causes the calcium phosphate in the bone to melt. Upon cooling, the molten bone solidifies into small, hard, white, translucent globules or "pearls" that resemble wax drippings. **Analysis of Incorrect Options:** * **A. Burns:** While thermal burns involve high heat, they typically cause charring or carbonization of the bone rather than the specific melting and recrystallization seen in electrical conduction. * **B. Scalds:** These are caused by moist heat (steam or hot liquids). The temperature is generally limited to 100°C, which is insufficient to melt bone minerals. * **C. Lightning strike:** While lightning involves massive voltage, the contact is instantaneous. The classic pathognomonic finding for lightning is the **Arborescent mark** (Lichtenberg figures or "fern-like" patterns) on the skin, not bone pearls. **High-Yield NEET-PG Pearls:** * **Joule’s Law:** $H = I^2RT$ (Heat is proportional to the square of current, resistance, and time). * **Resistance Hierarchy:** Bone (Highest) > Fat > Nerve > Muscle > Blood (Lowest). * **Electric Burn (Joule Burn):** Characterized by a central charred crater with raised, pale edges (endogenous burn). * **Metallization:** Deposition of metal ions from the conductor onto the skin, diagnostic of electrical contact.
Question 8: Arborescent marks or filigree burns are typically seen in which type of injury?
- A. Radiation
- B. Electrical burns
- C. Chemical burns
- D. Lightning strike (Correct Answer)
Explanation: **Explanation:** **Arborescent marks** (also known as **Lichtenberg figures**, filigree burns, or keraunographic marks) are pathognomonic of a **lightning strike**. These are not true thermal burns but are transient, reddish, fern-like, or tree-like patterns on the skin. They are caused by the extravasation of red blood cells into the superficial layers of the skin due to the massive electrical discharge (dielectric breakdown) following a lightning strike. These marks typically appear within an hour of the injury and usually disappear within 24 to 48 hours. **Analysis of Incorrect Options:** * **A. Radiation:** Radiation injuries typically present as erythema, desquamation, or chronic ulceration (radiodermatitis), depending on the dose and duration, but do not form branching patterns. * **B. Electrical burns:** High-voltage electrical injuries usually produce "entry" and "exit" wounds. A characteristic finding is the **Joule burn** (endogenous heat production) or a "crocodile skin" appearance at the contact site, rather than filigree patterns. * **C. Chemical burns:** These result in coagulative (acids) or liquefactive (alkalis) necrosis. The pattern depends on the flow of the liquid (trickle marks) but is not arborescent. **High-Yield Clinical Pearls for NEET-PG:** * **Pathognomonic Sign:** Lichtenberg figures are the most specific external sign of a lightning strike. * **Flashover Effect:** Lightning often travels over the surface of the body (flashover), which may paradoxically protect internal organs but can vaporize sweat, causing "zipper burns" or bursting of clothes. * **Ear Findings:** Rupture of the **tympanic membrane** is the most common clinical finding in lightning strike victims. * **Cause of Death:** Immediate death in lightning strikes is usually due to **cardiac arrest** (asystole) or respiratory paralysis.
Question 9: What is a 'brush burn'?
- A. An abrasion (Correct Answer)
- B. An electric burn
- C. A chemical burn
- D. A contusion
Explanation: **Explanation:** A **brush burn** is a type of **graze abrasion** (also known as a sliding or friction abrasion). It occurs when the skin surface is rubbed against a broad, rough, or blunt surface with significant lateral force. This friction generates heat, which can cause a superficial "burning" appearance, hence the name. **Why the correct answer is right:** * **Option A (An abrasion):** By definition, a brush burn involves the scraping away of the superficial layers of the epidermis (stratum corneum). It is commonly seen in road traffic accidents (e.g., "road rash") where a body is dragged across a tarmac or rough road surface. **Why the incorrect options are wrong:** * **Option B (Electric burn):** These are caused by the passage of electric current through the body, typically resulting in specific lesions like "Joule burns" or "entry/exit marks." * **Option C (Chemical burn):** These result from contact with corrosive substances (acids or alkalis) that cause coagulative or liquefactive necrosis of the tissue. * **Option D (Contusion):** Also known as a bruise, this is an infiltration of blood into the subcutaneous tissues due to the rupture of small vessels (capillaries) by blunt force, without a breach in the skin surface. **High-Yield Clinical Pearls for NEET-PG:** * **Direction of Force:** The direction of a brush burn can be determined by the **tags of skin** (epidermal tags) found at the end of the injury; the tags point toward the direction of the force. * **Antemortem vs. Postmortem:** Antemortem abrasions show signs of vital reaction (reddish-brown color, exudation of serum), whereas postmortem abrasions (parchmentization) appear yellowish and translucent. * **Graze vs. Scratch:** A graze involves a broad area (like a brush burn), while a scratch is a linear abrasion caused by a sharp-pointed object (like a nail or thorn).
Question 10: A 'black eye' is a type of:
- A. Patterned abrasion
- B. Ectopic abrasion
- C. Ectopic bruise (Correct Answer)
- D. Friction abrasion
Explanation: **Explanation:** A **black eye** (periorbital ecchymosis) is a classic example of an **ectopic bruise** (also known as a migrating or shifting bruise). **1. Why "Ectopic Bruise" is correct:** A bruise is typically found at the site of impact. However, an ectopic bruise appears at a site distant from the actual injury. In the case of a black eye, it often results from a **fracture of the anterior cranial fossa (cribriform plate)**. Blood tracks down by gravity through the subcutaneous tissues and collects in the loose areolar tissue around the eyes. It can also occur due to a direct blow to the forehead, where blood tracks downwards. **2. Why other options are incorrect:** * **Patterned Abrasion:** These occur when the object's shape is imprinted on the skin (e.g., tire marks or whip marks). A black eye is a collection of blood (hematoma/ecchymosis), not a superficial epithelial injury. * **Ectopic Abrasion:** This is a non-existent medical term; abrasions occur strictly at the point of friction/impact. * **Friction Abrasion:** Caused by tangential force or sliding across a rough surface (e.g., "road rash"). **High-Yield Clinical Pearls for NEET-PG:** * **Spectacle Hematoma:** If a black eye is bilateral and develops without direct trauma to the eyes, suspect a **Basilar Skull Fracture** (specifically the anterior fossa). * **Distinguishing Feature:** In a black eye caused by a skull fracture, the hemorrhage is limited by the **palpebral fascia** and does not extend into the subconjunctival space (unlike direct eye trauma). * **Color Changes:** Bruises change color over time (Red → Blue/Livid → Brownish → Green → Yellow → Normal) due to hemoglobin degradation. This is vital for **aging an injury**.
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