Ambulatory Paraparesis in a German Shepherd Dog

History

A 10-year-old castrated German shepherd dog was evaluated for a 2-month history of progressive ambulatory paraparesis. The client noted a lowered stance and gradual flexing of the patient’s pelvic limbs causing a sitting (vs standing) stance; the patient also had lowered tail carriage, was reluctant to jump, and seemed to be bearing weight only on the medial digits of his right pelvic limb. His tail became flaccid with decreased sensitivity but could still be wagged. The patient was receiving carprofen PO q12h, hyaluronic acid PO q12h, and Adequan (ie, polysulfated glycosaminoglycan) IM once monthly; the client claimed that Adequan was the most helpful for the patient’s neurologic function. Nontraditional therapies (eg, chiropractic adjustments, laser therapy) had been tried without noticeable improvement. No fecal or urinary incontinence had been noted.

The patient was an agility dog until 2 years prior, when he sustained a partial hamstring tear that had been reaggravated at least twice. The patient had tested negative for the SOD1 mutation associated with degenerative myelopathy.

Physical Examination

There was mild muscle wasting of the pelvic limbs and decreased anal and tail tone. General evaluation revealed no other significant abnormalities.

Neurologic Examination

• Mentation: Appropriate but quiet  

• Posture: Lowered rear stance

• Gait: Ambulatory with normal strength and function of the thoracic limbs; mild paraparesis with proprioceptive ataxia affecting the right more than the left pelvic limb.

• Postural reactions: Proprioceptive placing was normal in the thoracic limbs, decreased in the right pelvic limb, and absent in the left pelvic limb.

• Cranial nerves: All intact and unremarkable

• Spinal reflexes: Thoracic limbs were normal. Myotatic reflexes were normal in both pelvic limbs. Pelvic limb withdrawal reflexes were mildly decreased with a terminal kick noted on the left side.

• Spinal pain: The patient exhibited mild pain on palpation of the thoracolumbar vertebral column, and moderate pain on elevation of the tail and lumbosacral palpation via digital rectal evaluation.

Where would you localize this lesion?

Lesion Localization

L6–S3 spinal cord segments versus nerve roots versus peripheral nerves

Differential Diagnoses

(chronic, slowly progressive painful L6–S3 myelopathy, radiculopathy, or neuropathy)

• Disk protrusion with or without concurrent lumbosacral stenosis

• Neoplasia affecting the nervous tissue, vertebral bodies, meninges, or surrounding soft tissues

• Infectious or noninfectious inflammatory disease such as diskospondylitis, myelitis, radiculitis, or neuritis

• Trauma such as vertebral fracture, luxation, or hemorrhage.

Diagnostics

• Hematology, serum chemistry panel, and thoracic radiography were performed; no abnormalities were noted.

• Complete spinal MRI revealed multifocal intervertebral disc degeneration throughout the mid-thoracic, caudal thoracic, and lumbar vertebral column, with intervertebral disc herniation resulting in mild spinal cord compression at T13–L1, L1–L2, L2–L3, L5–L6, and L6–L7 (Figure 1). The L7–S1 intervertebral disc was also herniated, leading to severe bilateral nerve root compression at this location (Figure 2). The discs in the cervical and cranial thoracic spine were adequately hydrated.

Figure 1

Sagittal T2 weighted image of the caudal lumbar spine and sacrum. The L5–L6 (dashed white arrow), L6–L7 (thin white arrow), and L7–S1 (thick white arrow) intervertebral discs are protruded, which is consistent with intervertebral disc herniation.

Figure 2

Axial T2 image of the lumbosacral junction showing bilateral nerve root compression (white arrows)

Outcome

An L7–S1 dorsal laminectomy and discectomy surgery was performed to decompress the cauda equina. The interarcuate ligament was extremely hypertrophic, and the dorsal annulus of the lumbosacral disc was intact but thin. Following incision of the annulus, a large volume of calcified nucleus pulposus was extracted.

The patient was ambulatory without assistance within 12 hours of surgery. His urine stream was initially weak but normalized within 5 days. He was discharged on codeine PO q8h, gabapentin PO q8h, and carprofen PO q12h with instructions for 6 weeks of strict rest. At suture removal 9 days postoperatively, the patient demonstrated improved tail tone with lessening of the pelvic limb ataxia and paraparesis.