Most commonly involved nerve in Leprosy is -

Appeared in: UPPSC 2023

Explanation

Leprosy, caused by Mycobacterium leprae, has a predilection for cooler tissues of the body, including peripheral nerves.
The ulnar nerve is the most commonly affected nerve because it runs superficially at the elbow, making it cooler and more susceptible to invasion by the bacterium.
Palpable thickening of the ulnar nerve above the elbow is a cardinal sign of leprosy.
Damage to the ulnar nerve results in sensory loss of the medial one and a half fingers and motor weakness leading to a 'claw hand' deformity.

Option A: The posterior tibial nerve is frequently involved in leprosy, but not as commonly as the ulnar nerve.
Option C: The common peroneal nerve is the second most commonly affected nerve in leprosy, after the ulnar nerve.
Option D: The fibular nerve is another name for the peroneal nerve. As with the common peroneal nerve, it is frequently affected but is second in prevalence to the ulnar nerve.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Nerve involvement in Leprosy as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in the early detection of leprosy by performing sensory testing and palpating major nerve trunks (like the ulnar nerve) for thickening and tenderness during physical assessments.
Patient education is a key nursing intervention. Patients with sensory loss must be taught how to inspect their limbs daily for injuries, as they may not feel pain, and how to protect anesthetic hands and feet from trauma and burns.
Monitoring for and managing leprosy reactions (Type 1 and Type 2) is a critical nursing responsibility, as these reactions can cause acute nerve damage and worsening disability if not treated promptly with steroids.

How to Approach the Question

First, identify the core of the question: it asks for the 'most common' nerve affected by a specific disease, 'Leprosy'.
This is a factual recall question. Access your knowledge about the pathophysiology of leprosy.
Recall that M. leprae prefers cooler body temperatures.
Consider the anatomical locations of the nerves listed in the options. The ulnar nerve is very superficial at the elbow, the common peroneal nerve is superficial at the head of the fibula, and the posterior tibial nerve is deeper at the ankle.
Based on the temperature preference of the bacterium, superficial nerves are more likely to be affected. The ulnar nerve's superficial position at the elbow makes it the most vulnerable and therefore the most commonly affected nerve.
Evaluate the options based on this principle to select the most likely answer.

Concept Tested & Keywords

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E6 Medicine Davidson Principles Practice 24e p. 288-290

E6 Medicine Harrison 22e Part 2 p. 1510-1512

Practise the full UPPSC 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.