Page 412 - Canine Lameness

384 21 ­Neurorogico giNciN rAectNe Nolgi gim

Radiography is of some benefit, though, it rarely provides enough information to define or even
diagnose DLSS. Many clinically normal older dogs will have degenerative abnormalities on
radiographs, like spondylosis. However, conventional radiographs are indicated in patients having
signs consistent with DLSS, as part of a complete workup. Special attention should be paid to the
vertebrae (e.g. L7–S1 orientation, ventral spondylosis, erosive bony changes, facet changes, end
plate sclerosis or osteophytes, and intervertebral foramen size and shape), hips (conformation and
osteophyte presence), and intrapelvic structures (lymphadenopathy, prostate and colon/rectal
abnormalities, and bladder or urethral stones).
Advanced imaging studies are necessary to define and diagnose DLSS, with MRI being preferred
to CT for soft tissue detail and three‐dimensional analysis of anatomy. Images may show impinge-
ment of the cauda equina and/or L7 nerve(s) from a central vertebral canal lesion (IVD protru-
sion), foraminal protrusion, or dorsal interarcurate ligamentous compression. However, this does
not rule out the potential for disease elsewhere in the pelvic limbs, nor does it prove the compres-
sion is causing the clinical signs. Similar to radiographs, many older dogs that are apparently nor-
mal can have degenerative changes in the lumbosacral region. Furthermore, the apparent severity
of cauda equina compression does not correlate with the severity of clinical signs. Electrodiagnostics
can support diagnosis of a nerve disorder. Consequently, a final diagnosis of DLSS must be based
on historical and clinical presentation combined with neuroimaging findings.
Conservative management is generally pursued for mild cases; surgical decompression may be
warranted in more severe cases or those that fail medical management. Fecal and urinary inconti-
nence should insight urgency in considering surgical decompression, as chronicity carries a poor
prognosis in reversing these clinical signs.

21.3.1.4 Discospondylitis
Discospondylitis and associated osteomyelitis are typically bacterial (and less commonly fungal or
algal) infections that begin either at the cartilaginous end plates of the vertebral bodies and spread
to the IVD or remain confined to the vertebra, respectively (Thomas 2000). The L7–S1 disc space is
most commonly affected, but other spaces including those affecting the thoracic limbs can be
involved. Discospondylitis affects large, middle‐aged dogs most commonly, especially those used
for hunting, and male dogs outnumber females by about two to one.
Most patients affected with discospondylitis present with clinical symptoms associated with spi-
nal pain (e.g. decreased activity and unwillingness to jump). Other nonspecific clinical signs
include fever, weight loss, and anorexia. Presentation can be peracute or can wax and wane.
Lameness can be part of the presenting signs and may be unilateral or bilateral but more com-
monly affects the pelvic limbs. Chronic discospondylitis can cause a myelopathy or radiculopathy
if the infection extends into the surrounding soft tissues (e.g. muscles and ligaments). This can lead
to IVDH or instability resulting in vertebral subluxation.
With vague clinical signs, discospondylitis is notoriously difficult to diagnose. Imaging is critical
to establish the diagnosis of discospondylitis. Radiography (Figure 21.1A-C) is usually diagnostic
(Ruoff et al. 2018). However, radiographic abnormalities may not appear until two to six weeks
after onset of infection. Thus, normal spinal radiographs do not rule out a diagnosis of discospon-
dylitis. Nevertheless, radiographs are warranted in a dog presenting with poorly localizable pain,
paraspinal pain, and minimal to no neurologic deficits including lameness. Sedated radiographs of
the entire vertebral column are recommended. In one study, 40% of dogs had multiple lesions at
diagnosis and in almost 20% of cases, the number of affected disc spaces increased during the
course of treatment (Burkert et al. 2005). The earliest radiographic signs of discospondylitis appear
as subtle irregularity of the vertebral end plates. The IVD space may be narrowed due to destruction
of the disc. As the infection progresses, lysis of the vertebral end plates and osteolysis of adjacent
vertebral bodies becomes more pronounced. As bone regeneration occurs, there will be a variable