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Poliomyelomalacia in three dogs that underwent hemilaminectomy for intervertebral disk herniation
Case Description:
3 dogs were examined because of a sudden onset of signs of pain (1 dog) or paraparesis (2 dogs).
Clinical Findings:
Neurologic findings consisted of myelopathy affecting the lumbar intumescence (1 dog) and T3-L3 myelopathy (2 dogs). In all dogs, MRI revealed spinal cord compression caused by L3-4 disk herniation. All dogs underwent routine surgical decompression of the intervertebral disk herniation. During MRI and decompressive surgery, physiologic variables were monitored. Immediately after surgery, all dogs were paraplegic with pelvic limb neurologic dysfunction consistent with myelopathy affecting the L4 through caudal spinal cord segments.
Treatment And Outcome:
Within 24 hours after surgery, repeated MRI in all dogs revealed hyperintensity in the spinal cord gray matter of the lumbar intumescence on T2-weighted images. In the absence of neurologic improvement, dogs were euthanized at 3, 91, and 34 days after surgery. Postmortem microscopic examination of each dog's spinal cord at the lumbar intumescence revealed necrosis of the gray matter with relative white matter preservation suggestive of an ischemic injury.
Clinical Relevance:
Dramatic neurologic deterioration following decompressive surgery for intervertebral disk herniation in dogs may be associated with the development of poliomyelomalacia secondary to ischemia. In these 3 dogs, ischemia developed despite probable maintenance of normal spinal cord blood flow and perfusion during anesthesia. To exclude other causes, such as compression or hemorrhage, MRI was repeated and revealed hyperintensity of the spinal cord gray matter on T2-weighted images, which microscopically corresponded with ischemic neurons and neuronal loss.
Insights
Sudden paraparesis in dogs after surgery for intervertebral disk herniation may indicate developing poliomyelomalacia. This condition, characterized by spinal cord gray matter damage, can occur despite stable anesthesia and requires further investigation with MRI and postmortem analysis.
Area of Science:
- Veterinary Neurology
- Comparative Pathology
Background:
- Intervertebral disk herniation is a common cause of spinal cord compression in dogs.
- Surgical decompression is the standard treatment for acute cases.
Observation:
- Three dogs experienced sudden paraparesis following surgical decompression for L3-4 disk herniation.
- Post-operative MRI revealed spinal cord gray matter hyperintensity, indicative of ischemic injury.
- Histopathology confirmed gray matter necrosis consistent with poliomyelomalacia.
Findings:
- Dogs undergoing surgery for disk herniation can develop post-operative neurologic deterioration.
- This deterioration may be linked to ischemic injury leading to canine poliomyelomalacia.
- Spinal cord gray matter hyperintensity on MRI can signal ischemic damage.
Implications:
- Early recognition of post-surgical neurologic decline is crucial in canine spinal surgery.
- Understanding the mechanisms of ischemic injury can inform surgical and anesthetic protocols.
- Further research into preventing or managing post-operative ischemia is warranted.
