In the absence of nerve injury, weakness is rare in which trapezius segment?

• A. Middle trapezius
• B. Upper trapezius
• C. Lower trapezius
• D. All segments equally

Answer: (B)

The pattern of weakness across trapezius segments helps distinguish normal function from nerve injury. In a person without nerve injury, the upper trapezius is typically strong because lifting the shoulder and shrugging are common, well-rehearsed actions that keep this portion robust. If there were a nerve problem, you’d expect broader weakness across the trapezius, not just one part. So, isolated weakness of the upper trapezius is uncommon when the nerve supply is intact, making it the rare finding in this context.