Front Matter

Chapter 17 Diagnosis of and Treatment Options for Disorders of the Spine 435

and in most cases clinical signs occur when the
dogs are young. The spine of C2 is displaced
caudally at an angle, leading one to conclude
that the nuchal ligament is what is giving the
C2 subluxation its characteristic radiographic
appearance (Figure 17.13).

Hemi or block vertebra

Hemi or block vertebrae are usually incidental
findings seen on radiography involving the
mid‐thoracic vertebrae in the screw‐tailed
breeds (French Bulldogs, English Bulldogs,
Pugs, and others). These vertebrae are mal­
formed and can have quite an anomalous con­
formation (Figure  17.14). They can be
wedge‐shaped or fused and often cause an

extreme angle to the spine. The vertebrae are

foreshortened and cause crowding of the ribs.

The spinal alignments often are severe but the

dogs usually do not manifest clinical signs of

spinal cord dysfunction.

Congenital stenosis

Within the spinal column there are two abrupt

transitions of spinal mobility that probably have

the greatest forces placed upon them. Advanced

imaging of these areas in individuals with con­

genital stenosis seem to expose a smaller spinal

canal than is normal for the diameter of their

spinal cord and associated nerve roots (Fourie &

Kirberger, 1999; Drost et al., 2002; da Costa et al.,

2006). These changes are present from a very

early age. At the level of C6–T1 many large‐ and

giant‐breed dogs seem to have very little addi­

tional space around their spinal cords. A similar

loss of spinal canal volume is seen in many dif­

ferent breeds of dogs at the area between L5 and

S1. If the spinal canal is pathologically narrowed

in younger animals, clinical signs usually occur

before 1 year of age. These relatively stenotic

spinal canals predispose affected animals to spi­

nal cord compression. In large breeds that have

stenosis in the caudal cervical spinal canal,

abnormal gaits and postural deficits can be seen

in dogs as young as 12 weeks of age. Although

several names describe caudal cervical spinal

cord impingement, stenosis of the spinal canal

underlies these pathological conditions.

Figure 17.13 Lateral radiograph of an atlanto‐axial
subluxation. Notice the tilt (arrow) of C2 away from C1 and
the odontoid process (dens) riding up into the spinal canal.

Figure 17.14 Lateral thoracic radiograph demonstrating hemi or blocked vertebral abnormalities in this French
Bulldog. These vertebral changes were an incidental finding. Note the common bunching of the ribs (arrows).