The injury when weight lifting could have some consequences but these should be able to be diagnosed appropriately with the appropriate physical examination and testing.
A white line running across the cord could be a mach line. This is a shadow that can occur from tissue density (the shoulder), a metal artifact (a tooth filling) or something else. The fact that it is there exactly in the same place on every scan is somewhat weird but if not noted by the radiologists, is probably just an artifact.
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.