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Chapter 26: Lumbosacral Decompression and Foraminotomy 225

A B

Figure 26.3 Axial (A) and sagittal (B) CT of a dog with DLSS showing intervertebral disc space collapse, intervertebral disc protruding into the vertebral
canal and lateral recess of L7, as well as ventral spondylosis deformans and facetal joint osteophytes. Note the excellent bony definition and ability to evaluate
disc protrusion but poor detail for evaluating the individual nerves of the cauda equina and other soft tissue structures. Source: Courtesy of Dr. N. Fitzpatrick.

of abnormality on routine radiographs does not preclude a diagnosis MRI and CT findings must be carefully correlated with patient
of DLSS as instability and stenosis can occur without bony changes. history and physical examination findings to prevent over‐diagnosis
Routine radiography is also helpful in screening for other orthope- since imaging abnormalities have been documented to increase
dic abnormalities such as canine hip dysplasia. with age in asymptomatic human and canine patients [47,48].
Radiographic contrast studies are of little use in the diagnosis of
DLSS. Myelography can provide a diagnosis in dogs with a dural sac Treatment
that extends beyond the lumbosacral space but does not provide
information regarding compression of the cauda equina
[1–5,7,33–35]. Flexion–extension myelography can in some cases Conservative and Medical Therapy
Epidural infiltration of methylprednisolone acetate with fluoro-
help to discern dynamic lesions [33]. Discography and epidurogra- scopic guidance has been advocated as therapy for DLSS. In one
phy have been described but they can be difficult to perform and study, 79% of dogs showed improvement after single or multiple
interpret [33,35,36]. CT and MRI have become the gold standard infusions and 53% were judged as cured by owner questionnaire
for the diagnosis of DLSS.
[49]. More conservative treatment of DLSS can consist of rest and
antiinflammatory medications such as nonsteroidal antiinflam-
Computed Tomography matory drugs (NSAIDs) or corticosteroids as well as physical
CT allows visualization of sacral and facetal joint subluxation, ver- therapy. Other modalities (electrical stimulation, ultrasound ther-
tebral canal stenosis, IVD hypertrophy, and dorsal longitudinal lig- apy, laser therapy, and acupuncture) have been employed, but
ament hypertrophy. The L7 nerve root lateral recess and the L7–S1 there are few clinical data to support their use. Conservative ther-
intervertebral foramen are also visible on CT (Figure 26.3) [37–41]. apy is not typically appropriate for working or performance dogs
Compared with MRI, CT is more readily available, requires a since return to function after conservative or medical therapy
shorter anesthetic, and allows visualization of bone and mineral- often leads to recurrence of clinical signs [4,6,7].
ized soft tissues [41].
Surgery
Magnetic Resonance Imaging Surgery is indicated in dogs with DLSS that have not responded to
Soft tissues, both within and surrounding the spinal canal, are pain management and conservative therapy, or in dogs with neuro-
more discernible on MRI than CT [41]. Like CT, MRI allows for logical deficits. Surgery may also be the best option for performance
the collection of images in multiple planes but has distinct advan- or working dogs that need to return to activity. The primary goals
tages over CT for assessing IVD degeneration and visualizing the of surgery for DLSS include decompression of the cauda equina,
cauda equina and L7 nerve roots. Using MRI, the L7 nerve root release of entrapped nerve roots and, in some cases, stabilization to
can be followed for its entire path out of the lateral recess and prevent further collapse and degenerative disease.
through the intervertebral foramen. Images obtained in flexion The most commonly performed decompressive procedure is dorsal
and extension are useful for demonstrating the changes in the soft laminectomy, which can be combined with disc fenestration or
tissue and intermittent stenosis that can occur with dynamic discectomy. Foraminotomy, and in some cases partial or complete
lesions (Figure 26.4) [41–46]. facetectomy, can also be performed to achieve additional