Conditions of the Wrist Quiz

See Carpal tunnel syndrome. Option D is correct. The carpal tunnel is a narrow passage at the wrist formed by the carpal bones and roofed by the transverse carpal ligament (a strong band across the front of the wrist). The median nerve and the finger flexor tendons pass through it. In carpal tunnel syndrome the nerve is squeezed there, which causes tingling, numbness and pain in the thumb, index finger, middle finger and the lateral half of the ring finger, often worse at night. The palmar cutaneous branch of the median nerve leaves the main nerve in the forearm, above the wrist, and runs over the roof of the tunnel rather than through it. It supplies the skin of the lateral palm, including the thenar eminence (the fleshy pad at the base of the thumb). Compression within the tunnel therefore cannot affect it, and this skin is spared. This is a classic examination point: if the palm is numb, think of a lesion higher up the median nerve, or another nerve problem, rather than carpal tunnel syndrome alone.

• Usual pattern: Tingling and numbness of the thumb, index finger, middle finger and lateral half of the ring finger, often worse at night.
• Palmar cutaneous branch: It leaves the median nerve in the forearm and runs over the roof of the carpal tunnel, not through it.
• Spared skin: The lateral palm, including the thenar eminence, keeps normal sensation.

• Usual pattern: Tingling and numbness of the thumb, index finger, middle finger and lateral half of the ring finger, often worse at night.
• Palmar cutaneous branch: It leaves the median nerve in the forearm and runs over the roof of the carpal tunnel, not through it.
• Spared skin: The lateral palm, including the thenar eminence, keeps normal sensation.

• Usual pattern: Tingling and numbness of the thumb, index finger, middle finger and lateral half of the ring finger, often worse at night.
• Palmar cutaneous branch: It leaves the median nerve in the forearm and runs over the roof of the carpal tunnel, not through it.
• Spared skin: The lateral palm, including the thenar eminence, keeps normal sensation.

The skin supplied by the palmar cutaneous branch is spared. If you remember that this branch goes over the tunnel, not through it, you can predict the pattern.