Souza notes that a cervical rib seen on a cervical spine series is NOT pathognomonic for thoracic outlet syndrome. Which finding is being described as NOT pathognomonic?

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A cervical rib seen on a cervical spine X-ray is not diagnostic for thoracic outlet syndrome because it’s just an anatomical variant, and many people have cervical ribs without any symptoms. Thoracic outlet syndrome is diagnosed from a combination of symptoms, exam findings, and dynamic tests — no single finding definitively proves it. A cervical rib can contribute to narrowing at the outlet, but its presence by itself does not confirm the condition, and TOS can occur without a cervical rib as well. So imaging showing a cervical rib is a contributing factor, not a definitive diagnostic sign.

Brief notes on the other ideas: provocative tests like Roos or Adson can be suggestive but are not specific, and nerve conduction studies can indicate nerve involvement but are not unique to TOS. The key point is that there isn’t a single pathognomonic sign for thoracic outlet syndrome, and the cervical rib example illustrates that limitation.