Electrocution — MCQs
A 32-year-old male is brought for autopsy after being found on a railway track, suspected of suicide. Examination reveals joule burns on the fingers and multiple lacerated wounds on the body, with edges that do not gape and are closely approximated, and no positive vital reaction zone is present. Based on the autopsy findings, what is the most likely manner of death in this case?
Electrical contact burn usually causes
High tension electrical burns from overhead electrical lines can cause:
A body is discovered with burn marks as shown in the image, resembling a 'crocodile skin' pattern. What is the most likely cause?
A 25-year-old person was repairing the power plug of a geyser at home when he was electrocuted and died. The image shows:
What is the phenomenon shown in the image?
All are causes of wrist drop (condition shown in the image below) except:
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'?
Electrocution Indian Medical PG Practice Questions and MCQs
Question 1: A 32-year-old male is brought for autopsy after being found on a railway track, suspected of suicide. Examination reveals joule burns on the fingers and multiple lacerated wounds on the body, with edges that do not gape and are closely approximated, and no positive vital reaction zone is present. Based on the autopsy findings, what is the most likely manner of death in this case?
- A. Accidental (Correct Answer)
- B. Natural
- C. Homicidal
- D. Suicidal
Explanation: ***Accidental*** - The presence of **joule burns** on the fingers indicates **electrocution** from contact with an electrified railway line, which is the **cause of death**. - **Multiple lacerated wounds** with non-gaping edges and **absence of vital reaction zone** confirm these injuries were sustained **post-mortem** after the train struck the already deceased body. - **Key forensic principle**: Joule burns alone **cannot determine intent** - they only indicate electrical contact occurred. Railway electrocutions are **frequently accidental**, especially when individuals cross tracks unaware of live rails or overhead wires. - Without additional evidence of suicidal intent (suicide note, witness statements, deliberate positioning, psychiatric history), the **autopsy findings alone** are most consistent with **accidental electrocution** followed by post-mortem train impact. - The question asks for determination based on "autopsy findings" - physical evidence alone typically suggests accidental manner in railway electrocutions unless other contextual evidence proves otherwise. *Suicidal* - While the scenario mentions the person was "suspected of suicide," **autopsy findings cannot definitively prove suicidal intent** without corroborating evidence. - Joule burns on fingers are seen in both accidental and suicidal electrocutions and cannot distinguish between the two. - Suicide determination requires additional evidence beyond the physical autopsy findings described (e.g., positioning suggesting deliberate contact, farewell notes, witness accounts of deliberate action). *Homicidal* - Homicide would require evidence of **coercion**, restraint marks, defensive injuries, or signs of struggle, none of which are described. - Electrical homicide is rare and would typically show evidence of the victim being forcibly held against an electrical source. - The finger location of joule burns suggests **voluntary hand contact**, not forcible application by another person. *Natural* - Natural death refers to death from disease or internal pathology without external intervention. - The presence of **joule burns** (electrocution injury) and **traumatic lacerated wounds** clearly indicates an **unnatural cause of death** involving external factors.
Question 2: Electrical contact burn usually causes
- A. Superficial second degree burns
- B. First degree burns
- C. Third degree burns (Correct Answer)
- D. Deep second degree burns
Explanation: ***Third degree burns*** - Electrical burns often cause **deep tissue damage** because electrical current generates significant heat as it passes through the body, leading to destruction of all skin layers and underlying tissues. - The entry and exit points of an electrical current can appear relatively small, but the damage internally can be extensive and severe, justifying a **third-degree classification**. *Superficial second degree burns* - These burns involve the epidermis and superficial dermis, characterized by **blisters** and significant pain. - Electrical burns typically cause much deeper tissue destruction than what is seen in superficial partial-thickness burns. *First degree burns* - First-degree burns only affect the epidermis, causing **redness** and **mild pain** without blistering. - Electrical contact, even brief, almost invariably causes more severe damage than a superficial first-degree burn. *Deep second degree burns* - Deep second-degree burns extend into the deep dermis, often presenting with **blisters** and potentially some loss of sensation due to nerve damage. - While electrical burns can cause deep partial-thickness injuries, the current's path often leads to complete destruction of skin layers and underlying structures, making a full-thickness (third-degree) burn more common.
Question 3: High tension electrical burns from overhead electrical lines can cause:
- A. Myoglobinuria and Acute renal failure (Correct Answer)
- B. No ECG change will be seen in the first 24 hrs
- C. Severe alkalosis
- D. Blood vessels are spared
Explanation: ***Myoglobinurea and Acute renal failure*** - High tension electrical burns cause extensive **muscle damage** (rhabdomyolysis), leading to the release of **myoglobin** into the bloodstream. - **Myoglobinuria** can precipitate in the renal tubules, leading to **acute tubular necrosis** and subsequent **acute renal failure**. *No ECG change will be seen in the first 24 hrs* - Electrical burns often cause significant **cardiac irritation** and **arrhythmias**, which are typically identifiable on an **ECG** within the first 24 hours. - Damage to the heart due to the direct passage of current can result in various ECG changes, including **QT interval prolongation**, **ST segment changes**, and **tachyarrhythmias** or **bradyarrhythmias**. *Severe alkalosis* - Patients with significant electrical burns are more likely to develop **metabolic acidosis** due to tissue hypoperfusion, massive **cell death**, and the accumulation of **lactic acid**. - **Alkalosis** is not a typical presentation or complication of high tension electrical burns. *Blood vessels are spared* - Blood vessels, especially those with smaller diameters, are particularly susceptible to **thermal damage** from electrical current, leading to **coagulation** and **thrombosis**. - This vascular damage can result in **ischemia** and **necrosis** in affected tissues, often requiring significant debridement and reconstruction.
Question 4: A body is discovered with burn marks as shown in the image, resembling a 'crocodile skin' pattern. What is the most likely cause?
- A. Chemical burns
- B. High voltage electrical burns (Correct Answer)
- C. Scald burns
- D. Radiation burns
Explanation: ***High voltage electrical burns*** - **High voltage electrical burns** can cause severe damage, including charring and deep tissue necrosis, which can result in a contracted, leathery skin appearance often described as **"crocodile skin"** or **alligator hide**. - The alternating current (AC) associated with high voltage can lead to muscle tetany, causing the victim to clench onto the source, prolonging exposure and increasing the severity of damage and the characteristic burn pattern. *Chemical burns* - Chemical burns result from exposure to corrosive substances and typically manifest as **discoloration**, **blistering**, or **deep tissue damage** depending on the agent and duration of contact. - While severe, chemical burns usually do not produce the specific "crocodile skin" pattern of extensive charring and contraction seen with high voltage electricity. *Scald burns* - Scald burns are caused by hot liquids or steam and commonly result in **blistering**, **redness**, and superficial to partial-thickness skin damage without the deep tissue charring. - The pattern of injury would typically be distinct from the described "crocodile skin," often showing flowing or splash patterns. *Radiation burns* - Radiation burns occur due to exposure to high doses of radiation and can lead to **erythema**, **blistering**, and **skin breakdown** over time. - These burns develop progressively and often have a characteristic delayed presentation and pattern related to the radiation field, not the immediate charring seen with electrical injuries.
Question 5: A 25-year-old person was repairing the power plug of a geyser at home when he was electrocuted and died. The image shows:
- A. Joule burn (Correct Answer)
- B. Spark lesion
- C. Crocodile skin
- D. Scald
Explanation: ***Joule burn*** - This lesion is characteristic of an **electrical burn**, also known as a Joule burn or true electrical burn. The intense heat is generated by the passage of electrical current through body tissues (I²R heating), causing direct tissue destruction. - The appearance often includes a **central area of charring or necrosis** (dark, leathery, or blackened tissue) with a raised, crater-like edge, typically seen at entry and exit points of electrical current. *Spark lesion* - A spark lesion is typically a **smaller, superficial burn** caused by a momentary electrical arc or spark that jumps from conductor to skin without current passing through the body. - It usually presents as a **punctate or minor skin defect** with superficial charring and does not involve the extensive, deep tissue damage seen in Joule burns. *Crocodile skin* - "Crocodile skin" is a specific pattern seen in **high-voltage electrical injuries** where the epidermis separates and peels in a characteristic, polygonal pattern resembling crocodile hide. - This is a distinct manifestation of electrical injury, but the question describes a classic Joule burn with entry/exit point characteristics rather than this specific epidermal pattern. *Scald* - A scald is a burn caused by **hot liquid or steam**. - The appearance of scalds typically involves **blistering, redness, and peeling skin**, which is distinctly different from the charred, leathery appearance seen in electrical burns.
Question 6: What is the phenomenon shown in the image?
- A. Seen in antemortem burns
- B. Seen in postmortem burns
- C. Pugilistic attitude (Correct Answer)
- D. All are correct
Explanation: ***Pugilistic attitude*** - The image shows a body in a **"pugilistic attitude"** or **"boxer's pose"**, characterized by **flexion of the elbows, knees, and hips**, with clenched fists resembling a boxer's fighting stance. - This posture is due to **heat-induced coagulation and shortening of muscles** during exposure to high temperatures, such as in fires. - It occurs because **flexor muscles are stronger than extensor muscles**, and when heated, they contract more forcefully, pulling limbs into this characteristic flexed position. - This is a **postmortem phenomenon** that occurs regardless of whether the person was alive or dead when exposed to fire. *Seen in antemortem burns* - While the person may have sustained antemortem burns, the **pugilistic attitude itself is a postmortem change** that develops due to heat stiffening of muscles after death. - Antemortem burns show **vital reactions** such as blistering with protein-rich fluid, surrounding inflammation, soot in airways, and elevated carboxyhemoglobin levels - features not indicated by this posture alone. *Seen in postmortem burns* - While this statement is true (pugilistic attitude does occur in postmortem burns), the question asks for the specific **name of the phenomenon** shown in the image. - The posture results from **muscle protein denaturation and dehydration** when the body is exposed to temperatures above 65-70°C, causing muscle contraction and shortening. *All are correct* - This option is incorrect because "Seen in antemortem burns" is not an accurate description of the pugilistic attitude, which is specifically a **postmortem heat-related change**.
Question 7: All are causes of wrist drop (condition shown in the image below) except:
- A. Arsenic toxicity
- B. Lead poisoning
- C. Use of crutches
- D. Zinc poisoning (Correct Answer)
Explanation: ***Zinc poisoning*** - **Zinc poisoning** is not a characteristic cause of **wrist drop**, which is typically associated with **radial nerve palsy**. - While excessive zinc can cause copper deficiency and neurological issues, it does not directly lead to **radial nerve entrapment** or damage causing wrist drop. *Arsenic toxicity* - **Chronic arsenic poisoning** can lead to **peripheral neuropathy**, which may include motor weakness such as **wrist drop**. - The neurological damage is often dose-dependent and can affect various peripheral nerves. *Lead poisoning* - **Lead poisoning** is a well-known cause of **radial nerve palsy**, leading to **wrist drop**. - This is often seen in occupational exposures and can be quite specific to the **radial nerve**. *Use of crutches* - Prolonged or improper use of **crutches** can cause compression of the **radial nerve** in the axilla, leading to **crutch palsy**. - **Crutch palsy** manifests as weakness of the **forearm and hand extensors**, resulting in **wrist drop**.
Question 8: 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 9: 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 10: 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).
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