A patient with complex regional pain syndrome (CRPS) type I of the right lower limb has allodynia, oedema, and skin colour changes after a minor ankle sprain. Lumbar sympathetic block is being considered. Which feature DISTINGUISHES CRPS type I from CRPS type II?

• A CRPS type I follows a specific identifiable nerve injury; type II does not
• B CRPS type I only occurs in the upper limb; type II only in lower limb
• C CRPS type I requires sympathectomy; type II does not
• D CRPS type I occurs WITHOUT an identifiable major nerve injury; type II (causalgia) follows a specific major peripheral nerve injury ✓

Explanation

CRPS (formerly reflex sympathetic dystrophy/causalgia) is classified as: Type I (previously RSD) — develops after a noxious event without a demonstrable specific nerve lesion (e.g., after minor trauma, fracture, or surgical procedure); Type II (causalgia) — follows an identifiable, demonstrable major peripheral nerve injury. Both types share the same diagnostic criteria (Budapest criteria): pain disproportionate to the inciting event, allodynia/hyperalgesia, vasomotor/sudomotor/trophic changes, and oedema. The distinction matters for medicolegal and research purposes but treatment is similar.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.