Confusing case - help??

45 y/o guy, healthy, referred by ortho b/c he cant lift his right arm. this has been going on for 5 years. right shoulder MRI is fine, neck MRI is fine. he also has mild parethesias that he complains about in both hands and very mild in right foot. he has visible fasciculations in right deltoid. clear weakness in abduciton and flexion on right. weak reflexes.

NCS:
bilateral sensory median and radial are absent. ulnars are slow and relatively large for some reason.

MABC normal on right...

Confusing case - help??