A patient suffers a complete median nerve transection at the wrist. At follow-up examination of the thenar muscles, one muscle is found to retain partial voluntary contraction. This is explained by which anatomical finding?

• A The deep head of flexor pollicis brevis is supplied by the ulnar nerve ✓
• B Opponens pollicis is partly supplied by the ulnar nerve
• C Abductor pollicis brevis receives a dual nerve supply
• D Adductor pollicis has a median contribution in 80 percent of hands

Explanation

Flexor pollicis brevis has a superficial head innervated by the median nerve and a deep head usually innervated by the ulnar nerve, so it escapes complete paralysis in low median lesions. Abductor pollicis brevis and opponens pollicis are purely median and are fully paralysed. Adductor pollicis is entirely ulnar, so it functions normally here, but it lies in the adductor compartment rather than being a partially denervated thenar muscle.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.