MRIs vs. Other Imaging Modalities
Myelography is an invasive diagnostic test used to evaluate diseases of the spinal column. A contrast agent (dye) is injected into the spinal canal by inserting a needle (spinal tap) into the spinal column. Alteration of the flow of the contrast agent within the canal on radiographs allows the specialist to attempt to make a diagnosis. The results of a myelogram are less specific than those of an MRI, which reduces the chance of making an accurate diagnosis. The myelogram is less informative for planning surgery of spinal tumors and fails to provide adequate information about diseases within the spinal cord. The myelogram is an invasive test with inherent problems including inability to get a diagnostic study, deterioration of animal neurologic signs, seizures, and even death in rare instances. Myelography should be reserved for those animals with sudden loss of ability to use the rear-limbs or when an MRI is not readily available.
A Computerized Tomography (CT) scan is like an MRI; it is a safe, non-invasive advanced diagnostic test used to produce high quality images of the internal organs of the animal's body. As with radiographs, CT images are produced by the attenuation of x-rays in relation to the different density characteristics of the tissues of internal organs. In general, since the MRI has a lower incidence of false negative results and the images produced allow for a more detailed view of the animals' disease process, it is preferred to CT scan for neurologic disease.