Injuries and wounds: tetanic contraction in electric shock: practice question

A Forensic Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Forensic Medicine · Injuries and wounds: tetanic contraction in electric shock

Sample item

A farm worker grips a faulty live metal handle carrying 230 V alternating current and cannot release it until the supply is switched off by a bystander. Which mechanism explains his inability to let go?

AVentricular fibrillation with cerebral hypoxiaBTetanic contraction of forearm flexor musclesCThermal necrosis of the palmar tendonsDParalysis of the motor nerve at the elbow

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Tetanic contraction of forearm flexor muscles

Alternating current of household frequency produces sustained tetanic contraction of skeletal muscles. The flexors of the forearm are stronger than the extensors, so the hand clenches around the conductor and prolongs exposure. This is the reason for the 'no-let-go' phenomenon and why rescuers must first break the circuit.

Option by option

A. Ventricular fibrillation with cerebral hypoxia
Fibrillation causes collapse and loss of consciousness, after which the grip would be released.
B. Tetanic contraction of forearm flexor muscles (correct)
Correct. Sustained tetanic spasm of the stronger flexors keeps the hand closed.
C. Thermal necrosis of the palmar tendons
Heat injury to the tendons may occur later, but it does not cause the immediate grip.
D. Paralysis of the motor nerve at the elbow
Current causes muscle spasm, not flaccid motor nerve paralysis, which would open the hand.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is B, Tetanic contraction of forearm flexor muscles. Alternating current of household frequency produces sustained tetanic contraction of skeletal muscles.

Why is "Ventricular fibrillation with cerebral hypoxia" not the answer?

Fibrillation causes collapse and loss of consciousness, after which the grip would be released.

Why is "Thermal necrosis of the palmar tendons" not the answer?

Heat injury to the tendons may occur later, but it does not cause the immediate grip.

Why is "Paralysis of the motor nerve at the elbow" not the answer?

Current causes muscle spasm, not flaccid motor nerve paralysis, which would open the hand.

What concept does this question test?

It tests Injuries and wounds: tetanic contraction in electric shock in Forensic Medicine. The flexors of the forearm are stronger than the extensors, so the hand clenches around the conductor and prolongs exposure. This is the reason for the 'no-let-go' phenomenon and why rescuers must first break the circuit.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Injuries and wounds: tetanic contraction in electric shock?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.