Myelographic artifacts.

During myelography, injection of contrast outside the subarachnoid space can lead to false-negative or false-positive studies by not contrasting lesions or creating spurious signs. The production of high-quality myelograms and successful interpretation depend on knowledge of meningeal anatomy and the appearance of contrast material when injected between different meningeal layers. Opacification of the subdural space is a recently described technical complication in veterinary medicine, and increasingly is being recognized as a common problem during myelography. The purpose of this article is to describe the appearance of the different columns of contrast material that can be produced during myelography and to correlate these findings to the relevant anatomy, especially the subdural space.