Hirayama disorder is extremely rare (I’ve never seen it in 30 years) and would not show up on an EMG. Hirayama disorder is a cord problem (myelopathy) and as such, does not have neurological findings that would activate and EMG.
If you have unilateral muscle wasting in only one upper extremity, this could be from nerve compression in the neck or shoulder or a neurological disorder.
Straightening of the spine is a “finding” that might or might not have any bearing on your symptoms. Many individuals have this straightening without any symptoms at all so there has to be something more that is causing your problems. You need a good diagnostic spine surgeon to go over your history, physical examination and review all your images and consultations.
Dr. Corenman
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.