Page 231 - Adams and Stashak's Lameness in Horses, 7th Edition

Diagnostic Imaging 197

projection is made in the mid‐cervical region, and an ventral column at these locations appears as a thin line.
extended lateral one is made in the caudal cervical On extended lateral views, the dorsal column does not
VetBooks.ir different sites may be necessary. The contrast material horse are compressive lesions from cervical stenosis,
narrow, and the ventral column is increased in width.
region. Additional flexed and extended projections at
Most lesions detected via cervical myelograms in the
can be visualized via ventrodorsal radiographs over the
cranial and mid‐cervical regions, but because of the either bony or ligamentous, or the result of vertebral
thickness of the body area, it is usually not possible to instability (Figure 3.8). These lesions may cause substan­
visualize the contrast material in the caudal cervical tial narrowing, obliteration, or displacement of the con­
region of the adult horse. trast column. The most common sites of compression, in
On a normal myelogram study, several variations order of decreasing frequency, are C3–C4, C6–C7, C5–
need to be noted and not confused with false‐positive C6, and C4–C5. Suggested methods for assessment of
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lesions. On neutral lateral radiographs, there are areas a spinal cord compressive lesions include the reduction
of some degree of elevation of the ventral contrast col­ of 50% or more of the dorsal contrast column com­
umn at each intervertebral disk. On flexed lateral radio­ pared with the thickness of the subarachnoid space
graphs, there is also narrowing of the dorsal subarachnoid cranial to the narrowing, narrowing of the dorsal
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space, most frequently at C3–C4 and C4–C5, and the and ventral contrast columns by more than 50% in

A

B

C

Figure 3.8. (A) Normal flexed lateral myelogram of the cranial contrast columns narrowed by more than 50% and a narrowed
cervical region, showing contrast material in the subarachnoid spinal cord, suggesting dynamic cervical stenosis. (C) Extended
space and narrowing of the ventral column at C3–C4 (arrow). No lateral myelogram of the mid‐cervical region at the level of C4–
narrowing of the dorsal column or significant spinal cord C5, showing stenosis of the spinal canal on the cranial aspect of
compression is present. (B) Flexed lateral myelogram of the C5 with narrowing of the dorsal contrast column by at least 50%
cranial cervical region, showing ventral and dorsal (arrows) (arrow).