My Son Recently Had Shoulder Surgery Near The Rotator Cuff

My son recently had shoulder surgery near the rotator cuff After he began to heal when ever he would look down or to the side he would get dizzy then both of his arms have gone numb. They have done extensive testing for MS and have ruled it out. I think it has something to do with his neck but nothing shows on his MRI's or exrays, Could there be a small fracture in one of his Cervical Vertabraes?