What is the major disadvantage of interscalene brachial plexus block compared with other approaches?

What is the major disadvantage of interscalene brachial plexus block compared with other approaches?

• A. Not suitable for shoulder operations
• B. Large volumes of local anesthetic required
• C. Frequent sparing of the ulnar nerve
• D. Frequent sparing of the musculocutaneous nerve

Answer: (C)

The key idea is that interscalene block targets the upper trunk of the brachial plexus, which provides excellent anesthesia for the shoulder. However, it often does not block the lower trunk (C8-T1), from which the ulnar nerve arises. Because the ulnar nerve supplies sensation to the medial forearm and most of the little finger, patients frequently retain sensation and some motor function in the ulnar distribution after this block. That incomplete coverage is the major drawback when a procedure involves the hand or ulnar nerve territory, and it often necessitates an additional block or another approach to cover the ulnar distribution. The other statements don’t capture this clinically important limitation: interscalene blocks are particularly good for shoulder surgery, volumes can be minimized with ultrasound guidance, and musculocutaneous involvement is not the defining disadvantage in most cases.

The key idea is that interscalene block targets the upper trunk of the brachial plexus, which provides excellent anesthesia for the shoulder. However, it often does not block the lower trunk (C8-T1), from which the ulnar nerve arises. Because the ulnar nerve supplies sensation to the medial forearm and most of the little finger, patients frequently retain sensation and some motor function in the ulnar distribution after this block. That incomplete coverage is the major drawback when a procedure involves the hand or ulnar nerve territory, and it often necessitates an additional block or another approach to cover the ulnar distribution. The other statements don’t capture this clinically important limitation: interscalene blocks are particularly good for shoulder surgery, volumes can be minimized with ultrasound guidance, and musculocutaneous involvement is not the defining disadvantage in most cases.