Degenerative lumbosacral stenosis Flashcards
What are the different caudal locations of spinal cord termination based on size?
Large/giant breed: L4
Dogs < 10 kg: L6
Toy breeds and cats: L7
The dural sac extends a further 1 to 2cm beyond the terminal portion of the conus medullaris.
What are the specific nerves that make up the cauda equine?
S1, S2, S3 (sometimes extended to include L7)
What is cauda equina syndrome?
The term used to describe the clinical signs resulting from disease processes that involve the lumbosacral articulation that affect the nerve roots and/or the spinal nerves of the cauda equina.
What is the most common cause of cauda equina syndrome?
Lumbosacral stenosis
What abnormalities occur alone or in combination with degenerative lumbosacral stenosis?
- IVDH (normally type 2).
- Congenital osseous stenosis of the vertebral canal or intervertebral foramina.
- Sacral osteochondrosis.
- Proliferation of the joint capsule or ligaments.
- Osteophytosis of the articular processes.
- Epidural fibrosis.
- Instability or malalignment/subluxation of L7-S1.
- Transitional vertebrae.
Describe the pathophysiology of degenerative lumbosacral stenosis
Abnormal motion pattern predisposes to degeneration of the IVD. Degeneration of the IVD shifts loading to the zygaphophyseal joints and ventral vertebral bodies. Surrounding anatomic structures respond by proliferation and hypertrophy. Additional disc degeneration results in IVDH (type 2). A combination of these factors results in compression of nerve roots, with demyelination, axonal loss and inflammation.
Is degenerative lumbosacral stenosis more common in male or female dogs?
Male dogs. Mainly large breed.
What are some clinical signs associated with degenerative lumbosacral stenosis?
Crouched pelvic limb posture, pelvic limb lameness, pelvic limb root signature (mutilation of the limb), reluctance to jump or work.
Describe the nerves originating from the lumbar intumescence and the possible neurologic findings related to these nerves in cases of degenerative lumbosacral stenosis
What examination techniques may elicit pain responses at the lumbosacral articulation?
- Traction or extension of the tail.
- Direct digital pressure per rectum.
- Pressure on the articulation while elevating the thoracic limbs.
- As above but elevating the pelvic limbs and extending the hips (lordosis test).
- As above but hyperextending one pelvic limb at a time.
- Swinging the pelvic limbs side to side
Is severe neurologic dysfunction frequently seen in patients with degenerative lumbosacral stenosis?
No, generally mild. Often deficits relate to dysfunction of the fibular branch of the sciatic nerve (absent hock flexion during withdrawal testing). Pseudohyperreflexia of the patellar tendon may also be seen.
What is associated with a significantly worse prognosis in instances of degenerative lumbosacral stenosis?
Urinary and faecal incontinence
What are some differential diagnoses for degenerative lumbosacral stenosis?
Multilevel Hansen type II disc extrusion, diffuse idiopathic skeletal hyperostosis and degenerative myelopathy are common concurrent findings in dogs with suspected lumbosacral stenosis.
Is there a correlation between the severity of clinical signs and degree of cauda equina compression as seen on MRI?
No - severity is ultimately based on neurologic examination.
What diagnostics could be considered in the work-up of degenerative lumbosacral stenosis?
- Electrophysiologic testing (electromyography, motor nerve conduction velocity, sensory nerve conduction velocity, F-wave testing, cord dorsum potentials)
- Radiographs.
- CT/MRI.
In the pelvic limbs, electromyography should only be abnormal in muscles innervated by which nerve?
The sciatic. F-wave latencies would be prolonged with compressive radiculopathy.
What signs on radiography might be suggestive of degenerative lumbosacral stenosis?
Sacral osteochondrosis, transitional vertebrae, lumbosacral step, intervertebral disc vacuum phenomenon.
Describe some typical CT findings associated with degenerative lumbosacral stenosis
Collapse of the intervertebral disc space, end plate sclerosis, vacuum disc phenomenon ventral spondylosis, ventral subluxation of the sacrum, and elongation of the sacral laminae into the caudal aperture of the L7 foramen.
What is the most likely location of sacral osteochondrosis?
Dorsal aspect
Does CT imaging of the lumbosacral articulation in flexion or extension accentuate foraminal compression and IVD protrusion?
Extension
What are some common findings on MRI in dogs with degenerative lumbosacral stenosis?
Displacement or loss of epidural fat, intervertebral disc herniation, foraminal stenosis caused by soft tissue proliferation, ligamentous hypertrophy, and soft tissue proliferation of the zygapophyseal joint.
What is the imaging finding?
Describe the surgical landmarks for dorsal laminectomy of the lumbosacral joint
Describe access to the lumbosacral disc space for annulectomy and nucleus pulpectomy
When performing dorsal laminectomy for decompression of degenerative lumbosacral stenosis, which nerves of the cauda equina are located most laterally?
The L7 nerve root is lateral, exiting at the intervertebral foramen.
The S1, S2, S3 are found in a lateral to medial direction. The S1 nerve root is easily identified by the presence of a large spinal ganglion.
What techniques are described for distraction/fixation?
- Pins/screws and PMMA.
- Dorsal cross pinning (relies on the integrity of the dorsal spinous process of L7)
- Lag screws placed across the zygapophyseal joints.
- SOP plating
- Pedicle screw and rod fixation
+/- use of interbody device.
According to Lichtenhahn 2020 in Vet Surg, what sign on MRI is associated with L7 radiculopathy and foraminal stenosis?
Loss of foraminal fat signal (generally associated with clinical signs on the ipsilateral limb).
