Which finding is characteristic of thoracic outlet syndrome related to nerve compression?

• A. Median nerve compression
• B. Carpal tunnel syndrome
• C. Ulnar neuropathy with arm swelling and a positive Adson sign
• D. Radial nerve palsy

Answer: (C)

Thoracic outlet syndrome happens when structures crossing the thoracic outlet are compressed, often the lower trunk of the brachial plexus. When this lower trunk (C8–T1) is affected, symptoms appear in the ulnar distribution of the arm and hand and can be accompanied by venous changes that cause arm swelling. A provocative test like the Adson maneuver can reproduce compression and reduce the pulse, supporting a diagnosis of TOS with vascular involvement. So, seeing ulnar neuropathy signs along with arm swelling and a positive Adson sign is characteristic of thoracic outlet syndrome due to nerve compression. Median nerve issues point to carpal tunnel, and radial nerve palsy presents with a different pattern, so they don’t fit as well.