Ch 33 - Degenerative Lumbosacral stenosis Flashcards

1
Q

What kind of joint is the LS joint?

A

Amphiarthrosis (cartilaginous joint)

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2
Q

What are the embryological origins of the vertebral column and the spinal cord?
How does this contribute to the formation of the cauda equina?

A

Spinal cord is neuroectodermal origin, vertebral column is mesodermal origin.

They grow at different rates with the vertebral column outgrowing the spinal cord. As a result, the nerve roots of the terminal portion of the spinal cord have to course a longer distance to exit their respective intervertebral foramina

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3
Q

Where does the spinal cord terminate in various sized dogs?

A
  • Large/giant breeds - L4
  • Dogs under 15kg - L6
  • Toy breeds and cats - L7

Dural sac extends 1-2cm further caudally than the terminal conus medullaris and may extend into the sacrum in over 80% of dogs

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4
Q

Define cauda equine syndrome

A

clinical signs resulting from a disease process which involves the LS articulation and effects the nerve roots and/or spinal nerves of the cauda equina

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5
Q

What percentage of LS disc cultures are positive?

A

23%

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6
Q

What proinflammatory cytokines and growth factors are released with compressive radiculopathy?

A
  • TNFalpha
  • IL-6
  • IL-beta

Perpetuates the disease locally and within neural tissue and is an important mechanism in the induction of neuropathic pain

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7
Q

What is intermittent claudication?

A

Paroxysmal manifestations consistant with caudal lumbar pain or pelvic limb cramping, or weakness as a result of vascular compromise or compression of nerve roots in the cauda equina. Signs are exacerbated by activity

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8
Q

What nerves are effected by degenerative LS stenosis?
What reflex is most reliable?

A
  • Cranial tibial
  • Gastrocnemium
  • Perineal reflex and flexor-withdrawal reflex may be normal or depressed

Often, deficitis relate to sciatic dysfunction, causing a failure of hock flexion on withdrawal reflex.
May also be a pseudohyperreflexia of the patellar reflex due to loss of antigonistic muscle tone from the caudal muscle musculature

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9
Q

What is the only means of providing functional data about the cauda equina?

A

Electrophysiologic testing

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10
Q

What are the most consistent radiographic signs suggestive of LS stenosis?

A
  • Sacral osteochondrosis
  • Transitional vertebrae
  • LS step formation
  • LS disc vacuum phenomenon
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11
Q

What are the main CT findings consistent with LS stenosis?

A
  • Loss of epidural fat
  • Abnormal soft tissue density in intervertebral foramina
  • Buldging of LS disc
  • Displacement of dural sac
  • Subluxation and osteophytosis of zygapophyseal joints
  • Compressed and inflammed tissue will often contrast enhance

MRI findings are similar with the high signal fat getting replaced by hypointense material (disc vs fibrosis vs bony proliferation)

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12
Q

What is the success rate of medical management?

A

55%

79% improvement with 1mg/kg methypred epidural. 3 injections (1st injection, 2 weeks and 6 weeks later)

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13
Q

What are the indications for surgical stabilisation?

A
  • Moderate to severe neurological signs
  • Pain
  • Ventral subluxation of S1
  • To prevent further development of instability
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14
Q

How is the S1 nerve root identified?

A

Large spinal ganglion at the level if the LS IVD

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15
Q

What are the 2 approach options for a foraminotomy?
What can be used to enhance visualisation?

A
  • Dorsally through a dorsal laminectomy
  • Laterally without a laminectomy

Can use endoscopy to improve visualisation.
A osteotomy of the wing of the ilium has been described

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16
Q

What options are available for physical distraction of the LS joint prior to stabilisation?

A
  • Modified Gelpi retractors
  • Distractor on preplaced screws
  • T-handle distractor

Distracted until correct anatomical position of the zygapophyseal joints is attained

17
Q

List some techniques of LS stabilisation

A
  • Pins/screws and PMMA
  • Dorsal cross-pinning
  • Lag screws across zygapophyseal joint (placed ina ventrolateral direction at 30-45 degree angle in relation to sagittal plane)
  • SOP
  • Pedicle screw rod fixation
  • 3D printed titanium implants
18
Q

What is the prognosis with surgery?

What is the main known poor prognostic indicator?

A

Good to excellent outcome in 73 - 93%
Recurrence in 18% (3 - 54.5%)

Presence of urinary or faecal incontinence and duration of urinary incontinence (over 1m) associated with a poor prognosis.
Also older and more affected dogs improved less than younger and less affected dogs.

Only 41% military dogs returned to normal function. 38% improved and 20% never returned to work.