CT myelography is often done following standard myelography. CT provides exquisite spatial resolution. The acquisition of slices through a specific abnormal area previously identified on standard myelography may more clearly define the exact location and side of the lesion along the vertebral column. This is particularly important for further defining the extent and sidedness of disc extrusion prior to surgery, although is often employed for any disease entity causing a focal abnormality on a standard myelogram.