Hi, It sounds like you are experiencing a complex and challenging medical condition. Based on your description, it seems that you have already undergone several diagnostic tests, including nerve conduction studies, MRI scans, and blood tests. These tests have ruled out some possible causes but have not provided a definitive diagnosis. Since your nerve conduction studies have shown active muscle damage, treatment should focus on addressing the underlying nerve problem. Steroids may help reduce inflammation and prevent further muscle damage, but it is important to consult with your doctor about potential side effects and any other medications or supplements you are taking. A nerve biopsy may provide additional information about the cause of your muscle atrophy, but as your doctor has pointed out, it may also remove healthy muscle tissue and further weaken your arm. Therefore, it is important to carefully consider the risks and benefits of this procedure with your doctor. It is also a good idea to seek a second opinion from a specialist who has expertise in nerve and muscle disorders, such as a neuromuscular specialist or a neurologist who specializes in electromyography (EMG). They may be able to provide further insight and suggest alternative treatment options. Finally, it is essential to maintain regular follow-ups with your doctors and report any changes in symptoms, as this will help them track your progress and adjust your treatment plan as needed. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician