A patient with symptoms suggestive of median nerve compression at the wrist is found to have diminished sensation over the skin of the thenar eminence itself. Which statement best explains this finding?
- A It indicates compression proximal to the origin of the palmar cutaneous branch, such as in pronator syndrome ✓
- B It confirms compression within the carpal tunnel, since this skin is supplied by the recurrent motor branch
- C It indicates a coexisting ulnar nerve lesion at Guyon's canal
- D It is a normal variant, as the thenar eminence skin is supplied by the lateral cutaneous nerve of the forearm
Correct answer: A. It indicates compression proximal to the origin of the palmar cutaneous branch, such as in pronator syndrome
Explanation
The palmar cutaneous branch of the median nerve arises about 5 cm proximal to the flexor retinaculum and passes superficial to it, supplying the skin of the thenar eminence. Because it lies outside the carpal tunnel, its territory is spared in classic carpal tunnel syndrome. Sensory loss over the thenar eminence therefore localises the lesion more proximally, as in pronator syndrome, where the main median nerve is compressed between the heads of pronator teres.
Reference: Snell's Clinical Anatomy by Regions, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.