Page 1163 - Small Animal Internal Medicine, 6th Edition

CHAPTER 65 Disorders of the Spinal Cord 1135

Prognosis ACUTE INTERVERTEBRAL
Prognosis for recovery depends on the site and severity of DISK EXTRUSION
VetBooks.ir injury. Unstable cervical vertebral fractures are associated The intervertebral disks are composed of an outer fibrous
layer (annulus fibrosus) and a gelatinous center (nucleus
with very high mortality at the time of trauma and also in
the perioperative period. Prognosis for recovery is good if
replaced by fibrocartilage. In some dogs, particularly the
affected animals do not die acutely from respiratory dysfunc- pulposus). With normal aging the nucleus is gradually
tion. Animals with thoracic and lumbar spinal cord injury chondrodystrophoid breeds, the nucleus matrix degenerates,
and intact voluntary motion have a good prognosis for dehydrates, and mineralizes, making these dogs prone to
return of full function. Animals that are paralyzed but retain acute disk rupture. Acute extrusion of mineralized nucleus
deep pain and normal bladder function have a fair prognosis pulposus into the spinal canal through the dorsal annulus
for recovery, although they may have residual neurologic causing bruising or compression of the spinal cord is classi-
deficits. Animals presenting after spinal trauma with no deep fied as a Hansen type I IVD extrusion (Fig. 65.5). This type
pain sensation rarely recover. Lesions of the white matter
producing strictly UMN signs may have a better prognosis
for full recovery than lesions affecting clinically important
LMNs at the cervical or lumbar intumescence. In any animal
with paralysis caused by a spinal cord injury, if no signs of
improvement are evident by 21 days after injury, the prog-
nosis for recovery is poor.

HEMORRHAGE/INFARCTION
Nontraumatic hemorrhage into the spinal canal causing
acute neurologic deficits and sometimes pain (i.e., hyperes- NP
thesia) has been recognized in young dogs with hemophilia A
A, dogs of any age with von Willebrand disease, dogs and
cats with acquired bleeding disorders (i.e., warfarin intoxica-
tion, thrombocytopenia, disseminated intravascular coagu-
lation), dogs with vascular anomalies (i.e., aneurysms,
arteriovenous fistulas), and dogs and cats with primary or
metastatic spinal neoplasia that bleeds (i.e., lymphoma, hem-
angiosarcoma). Signs occur acutely and are minimally pro-
gressive, with neurologic signs reflecting the site and severity
of spinal cord damage or compression. Bleeding into the
subarachnoid space can cause inflammation (meningitis)
and pain. Antemortem diagnosis usually requires advanced
diagnostic imaging (i.e., MRI), although identification of a B
systemic bleeding disorder or neoplasia can suggest the diag-
nosis. Treatment should be initiated to resolve the cause of
bleeding, and surgical decompression of the spinal cord will
rarely be required.
Spinal cord infarction by a blood clot is a rare cause of
peracute neurologic dysfunction in dogs and cats. Signs
are referable to the site and severity of the vascular com-
promise. Blood stasis, endothelial irregularity, hyper-
coagulability, and impaired fibrinolysis are all known
predisposing factors for thromboembolism (see Chapter
12). Cardiomyopathy, hyperadrenocorticism, protein-losing
nephropathy, immune-mediated hemolytic anemia, heart-
worm disease, vasculitis, and disseminated intravascular C
coagulation have all been associated with an increased
risk of systemic thrombosis and can occasionally result FIG 65.5
in regional spinal cord infarction. Treatment consists of (A) Normal relationship between the intervertebral disk and
spinal cord. (B) Hansen type I disk extrusion, wherein the
general supportive care and anticoagulant medications to NP herniated into the vertebral canal through a ruptured
decrease the risk of further infarction, but antemortem annulus fibrosus. (C) Hansen type II disk protrusion, with
definitive diagnosis is difficult and prognosis for recovery bulging of the thickened annulus into the vertebral canal.
is poor. NP, Nucleus pulposus.