Paralysis of which nerve produces 'Ape thumb deformity'?

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

Explanation

Ape thumb deformity is the classic sign of a low median nerve lesion.
The median nerve innervates the thenar muscles (Opponens Pollicis, Abductor Pollicis Brevis, and superficial head of Flexor Pollicis Brevis), which are responsible for thumb opposition.
Paralysis of these muscles causes them to atrophy, leading to a flattening of the thenar eminence.
As a result, the thumb cannot be opposed and falls back in line with the palm, adducted and laterally rotated.

Option A: Paralysis of the axillary nerve affects the deltoid and teres minor muscles.
Option B: Paralysis of the radial nerve primarily affects the extensor muscles of the wrist and fingers.
Option C: Paralysis of the ulnar nerve affects the intrinsic muscles of the hand, including the interossei and the medial two lumbricals.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Peripheral nerve injuries of the upper limb and their associated clinical deformities as background academic context rather than a clinical decision trigger.
Ape thumb deformity severely impairs hand function, especially tasks requiring grip, pinch, and fine motor manipulation.
Nurses must assess motor and sensory function distal to any upper limb injury (e.g., fractures, carpal tunnel syndrome) to detect nerve compromise early.
Nursing care for patients with median nerve palsy includes passive range-of-motion exercises to prevent contractures and patient education on protecting the hand from injury due to sensory loss.

How to Approach the Question

First, identify the key term in the question: 'Ape thumb deformity'. This is a specific clinical sign.
Access your knowledge of peripheral nerve anatomy and function in the upper limb.
Systematically consider each option:
Axillary nerve: Relate it to the shoulder (deltoid muscle).
Radial nerve: Associate it with extensors (wrist drop).
Ulnar nerve: Connect it to the intrinsic muscles and the 4th/5th fingers (claw hand).

Concept Tested & Keywords

Concept Tested: Peripheral nerve injuries of the upper limb and their associated clinical deformities.
Stem keywords: Paralysis, nerve, Ape thumb deformity
Lead-in keywords: produces

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E6 Anatomy Workbook HumanAnatomy Vol 1 p. 76-78

E6 Anatomy BDChaurasia V1 10e p. 61-63

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