Which symptom distribution is more consistent with thoracic outlet syndrome due to nerve compression?

Which symptom distribution is more consistent with thoracic outlet syndrome due to nerve compression?

• A. Numbness/tingling on the medial forearm and 4th-5th fingers
• B. Edema and erythema
• C. Painful overhead activity
• D. Weakness of the deltoid

Answer: (A)

Thoracic outlet syndrome from nerve compression typically affects the lower portion of the brachial plexus (C8–T1). This nerve bundle supplies sensation to the medial forearm and the ulnar side of the hand, including the 4th and 5th digits. So numbness or tingling in the medial forearm and in the 4th–5th fingers is the classic sensory pattern of neurogenic TOS. The other patterns point to different problems: edema and erythema suggest vascular compression rather than nerve compression; pain during overhead activity fits impingement or rotator cuff issues; and isolated deltoid weakness points to axillary nerve involvement (C5–C6). Hence, the numbness/tingling in that specific distribution best matches nerve compression in TOS.

Thoracic outlet syndrome from nerve compression typically affects the lower portion of the brachial plexus (C8–T1). This nerve bundle supplies sensation to the medial forearm and the ulnar side of the hand, including the 4th and 5th digits. So numbness or tingling in the medial forearm and in the 4th–5th fingers is the classic sensory pattern of neurogenic TOS.

The other patterns point to different problems: edema and erythema suggest vascular compression rather than nerve compression; pain during overhead activity fits impingement or rotator cuff issues; and isolated deltoid weakness points to axillary nerve involvement (C5–C6). Hence, the numbness/tingling in that specific distribution best matches nerve compression in TOS.