Hey Bizi,

I am so sorry that your niece has to go through this.

But I don't understand how the neuro cannot understand pain and numbness in the arms?

I have a theory but could be totally off.

If her neck has no curve the the cervical spine is unstable and when she is moving around, it moves around too much likely and it irritaing some of those nerve roots which would signal pain and numbness.

You would not be able to see this on an MRI because when you lie in that thing she would look stable even if the neck has not curve. Have they dowe flexion and extension xrays? It might show how the spine is moving in real life and show where the pain is coming from. A chiro might be able to do these for her if the neuro won't.