Why do a Myelogram?

A myelogram is a diagnostic tool used to determine cord compression in the potential surgical candidate. Even when the horse shows obvious compression on standing films, the myelogram is needed to show if there is more than one level of compression. Cord compression is determined by measuring the dorsal and ventral dye column in both neutral and flexed positions. Ratio measurements are made by using a special software program on each digital radiograph taken during the myelogram.

What is a myelogram and how is it performed?

A myelogram is performed under IV anesthesia to check compression of the spinal cord. With the widespread use of digital radiography, it is not always necessary to refer to a university or referral center. A myelogram involves an injection of an iodine based fluid into the spinal canal that will outline the spinal cord replacing the clear radiolucent cerebrospinal fluid when viewed by radiographs.

The myelogram is accomplished by carefully inserting a spinal needle into the space between the first and second cervical vertebra (A-O space). Feeling a "pop" indicates penetration of the protective membrane (dura mater). The CSF (cerebrospinal fluid) is withdrawn through a long extension tube and then the dye is injected over a three-minute period of time. A series of radiographs are then taken with the cervical vertebra in neutral, flexed and extended positions.

Compression needs to be at least 50% reduction in width when compared to the width of the dye column in a neutral position. 

After reviewing the myelogram, your horse might show a single spinal canal compression. This is referred to as a "single level" and will require one Seattle Slew implant. Two compressions would be considered a "double level" requiring two Seattle Slew implants. If your horse has a negative myelogram, no compressions, it is still worth the time and effort for the client and patient.

To get a better visual understanding of how a myelogram is done you can watch a myelogram presentation on

Click here for information on a nuclear scan.