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My FA2018 has “C7” bolded, meaning it is the main nerve root. But I also got this one wrong so I can’t be much help besides that.
Honestly just a guess but I have this vague understanding that intrinsic hand muscles are C8-T1 so we might’ve expected more hand motor findings as well with a C8 lesion.
I narrowed it down to C7 using the fact that the C7 myotome is elbow extension. I also learned that the C7 nerve root was the main contributor to the triceps DTR so I just went with that.
They also mentioned that the person had weakness pronating the right forearm which is performed by the biceps. Biceps is innervated by the musculocutaneous nerve which is C5-C7 and that's what helped me pick C7 > C8.
Sorry, I thought the biceps was a supinator of the forearm?
yes.. its the supinator not pronator