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 +0  (nbme22#1)

I’m confused about this one. Weakness of extension and pronation of the right forearm, with a decreased triceps muscle stretch reflex. The answer was C7 nerve root, but how are you able to localize to C7 and not C6 or C8? I figured that extension is radial, C5-T1, and pronation is median, also C5-T1. Triceps reflex is C7-C8 (FA2019 says C6-C7). How would you narrow down to just C7 damage?

txallymcbeal  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.
mnemonia  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.
theecohummer  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.
mchu21  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.
mcl  Sorry, I thought the biceps was a supinator of the forearm?
henoch280  yes.. its the supinator not pronator




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