Which neurologic exam finding would be least helpful in differentiating thoracic outlet syndrome from other neck-arm conditions?

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Thoracic outlet syndrome is a peripheral compression affecting the brachial plexus or vessels as the arm moves through the outlet. When trying to distinguish it from other neck-arm conditions, you look for signs that localize to peripheral nerves or the lower brachial plexus and that can be reproduced with positioning or provocative maneuvers. Findings such as weakness or sensory changes in the intrinsic hand muscles and the ulnar distribution, or patterns consistent with lower trunk involvement, fit with a peripheral outlet issue and help separate TOS from conditions like nerve entrapment at a peripheral site or a single nerve root problem.

Cervical myelopathy, however, points to a central spinal cord problem. It produces long-tract signs and upper motor neuron findings—things like hyperreflexia, a Babinski sign, clonus, and gait disturbances, often with bilateral symptoms or a sensory level. These central signs are not typical of a peripheral outlet compression and thus don’t help distinguish TOS from other neck-arm conditions in the same way peripheral patterns do. In fact, they steer you toward evaluating a central cord process rather than a peripheral outlet issue, making cervical myelopathy the least helpful finding for differentiating TOS from other neck-arm conditions.