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Pathology · single question

Allodynia is BEST explained by which mechanism?

  1. Referral of pain from a distant visceral structure
  2. An exaggerated response to a stimulus that is already painful
  3. Complete loss of sensory input from the affected region
  4. A lowered firing threshold of nociceptive neurons, so that innocuous stimuli are perceived as painful
Show answer and explanation

Correct answer: D. A lowered firing threshold of nociceptive neurons, so that innocuous stimuli are perceived as painful

  • A. ❌ Referred pain is perception of pain at a site distant from its source; it is not defined by the threshold change.
  • B. ❌ An exaggerated response to an ALREADY painful stimulus is HYPERALGESIA — related, but not the same term.
  • C. ❌ Complete sensory loss is anesthesia; painful anesthesia is anesthesia dolorosa, a different phenomenon.
  • D. ✅ CORRECT — ALLODYNIA is pain evoked by a NORMALLY NON-PAINFUL stimulus — light touch, a breeze, brushing. Peripheral and central sensitization lower the activation threshold of nociceptive pathways so that low-threshold mechanoreceptor input is decoded as pain.

Note: Vocabulary set: allodynia (non-painful stimulus → pain) · hyperalgesia (painful stimulus → exaggerated pain) · paresthesia (abnormal but not unpleasant sensation) · dysesthesia (abnormal AND unpleasant).

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