PHII - Neuro > CH33- LS > Flashcards

CH33- LS Flashcards

(58 cards)

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1
Q

• What is the cauda equina/how is it formed?

A

• S1, S2, S3 and caudal nerve roots
• Caudal nerve roots of S1 through the caudal nerve roots. When the spinal cord develops it does not develop at the same rate at the vertebral column therefore the spinal cord stops before the vertebral segments. The caudal nerve roots travel within the vertebral canal before exiting at the appropriate foramen.

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2
Q

• Where does the spinal cord end in large/giant breeds, small breeds < 15kg, toy breeds and cats?

A

• Giant/large -> L4
• Small breeds -> L6
• Toy breeds/cats -> L7

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3
Q

• Where does the dural sac extend to?

A

• 1-2cm farther than the conus medullaris

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4
Q

• What are the borders of the intervertebral foramen?

A

• Zygapophyseal joint and articular processes, pedicles, vertebral body and dorsolateral part of the IV discs

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5
Q

• What passes through intervertebral foramen (what structures are different in the thoracic vs lumbar spine?

A

• Spinal nerve
• Thoracic spine - dorsal intercostal arteries
• lumbar - lumbar arteries

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6
Q

• What surrounds the cauda equina (dorsal, dorsolateral, lateral, ventral)?

A

• Dorsal - lamina, yellow ligament
• Dorsolateral - articular processes, zygapophyseal joints/capsules
• Lateral - pedicles
• Ventral - bodies of L7/sacrum, dorsal longitudinal ligament, dorsal AF,

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7
Q

• What do the nerves of the lumbar and sacral spinal nerves innervate?

A

• Exit the canal and form the lumbosacral plexus
• PLs, bladder, perineum, anal sphincter

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8
Q

• What is cauda equina syndrome?

A

• Clinical signs that affect L7-S3 cauda equine nerves

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9
Q

• What is lumbosacral stenosis (consider 9 anatomic causes)?

A

• Multifactorial degenerative disorder that in combination or alone causes neural or vascular compression of the cauda equina.
• IVDD - type 2 > type 1
• Congenital vertebrae
• Congenital stenosis of canal or intervertebral foramen
• OA of the joints
• Osteochondrosis of the sacrum
• Epidural fibrosis
• Tethered cord syndrome
• Low grade bacterial infections

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10
Q

• What portion of LS discs test positive for bacteria when cultured?,

A

• 23%

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11
Q

• Name the structures identified in this image.

A

• Bulging annulus fibrosis - Hansen type 2
• Thickening of the dorsal aspect of the annulus fibrosis
• Spondylosis deformans
• Osteophyte formation around L7 joint
• Thickening of the joint capsule
• Thickening of the yellow ligament
• Degeneration of disc leads to narrowed disc space, leading to what change in biomechanical forces (thereby leading to changes seen with LS stenosis)?
• Axial force on disc transitions to more peripheral force on vertebra-
• Zygapophyseal joints
• Vertebral bodies
• Results in hypertrophy and proliferation -> yellow ligament, osteophytes, ventral spondylosis

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12
Q

• List 5 structural changes to LS space due to altered biomechanical forces

A

• Yellow ligament hypertrophy
• Epidural fibrosis
• Osteophyte formation
• Ventral spondylosis
• Bulging of annulus -> T2 protrusion

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13
Q

• Name the type of injury/(what happens to the nerves) that occurs to the nerves in response to this structural change?

A

• Compression -> demyelination and axonal loss and inflammation

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14
Q

• What is involved in compressive radiculopathy?

A

• Compression leads to inflammation and axon degeneration
• Cytokine upregulation causes neuropathic pain and SC sensitization via astrocytes and glial cells
• Compromise circulation = intraneural edema
• Chronic compression leads to fibrosis

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15
Q

• List 6 exam techniques to ID LS pain in dogs?

A

• 1-traction/extension ot tail
• 2-Direct digital pressure per rectum to LS disc or promontory
• 3-Percutaneous apply pressure over the dorsal LS while standing the animal in extended position, thoracic limbs elevated
• 4-Percutaneous apply direct pressure over LS articulation while elevating pelvic limbs few cm off ground + extending hips
• “Lordosis “ test
• 5-Hyperextending one pelvic limb at a time while percutaneously applying direct pressure over dorsal LS articulation
• 6-Rotation the lumbosacral articulation by swinging pelvic limbs from side to side

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16
Q
  • What are the normal clinical signs present in LS stenosis? What is NOT typically present?
A
  • NOT ataxia or postural deficits
  • Abnormal tail carriage
  • LS pain
  • Decreased withdrawal due to sciatic dysfunction
  • INCREASED patellar reflex (due to loss of sciatic function- psuedohyporeflexia)
  • Urinary and fecal incontinence
  • Decreased perineal reflex
  • Neurogenic muscle atrophy
  • Reluctance to jump or work
  • Single or both legs affected by pain
  • Self-mutilation of the PLs or genitals
  • Crouched pelvic limb posture
  • Root signature pain
  • Intermittent claudication -> signs come and go with an activity
  • Kyphosis from severe LS pain and root signature pain in the LPL.
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17
Q

• List 12 differential diagnoses for LS stenosis. 519

A

• Hip dysplasia
• BIlateral cruciate
• Neoplasia
• Vertebral fracture
• Discospondylitis
• Iliopsoas myopathy
• DM
• Iliac artery thromboembolism
• Meningomyelitis
• Prostatic disease
• Anorectal disease
• Polymyositis

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18
Q

• Name 5 diagnostic tests.

A

• Orthopedic and neurologic exam
• Radiographs
• CT
• MRI
• Electrophysiologic testing
• Electromyography - muscle
• Motor nerve - direct evoked potentials, motor nerve conduction, F-wave testing)
• Sensory - sensory nerve conduction, cord dorsum potentials
• Abdominal ultrasound

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19
Q
  • What dictates the severity of the LS disease?
A
  • Neurologic exam
  • Findings on MRI do not always correlate with severity of clinical signs and there is moderate degree of agreement between MRI and CT
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20
Q

• What changes to somatosensory evoked potentials and nerve conduction assays are expected with LS?

A

• Somatosensory potentials - latency of tibial nerve prolonged
• F-wave latencies are also prolonged

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21
Q

• Describe this radiograph.

A

• Arrow -> Cranial lamina of the sacrum telescoping into the intervertebral foramen of L7
• Arrowhead -> Vacuum disc phenomenon (gas in the disc space)
• Star -> Incomplete fusion of the sacral body suggesting transitional vertebra

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22
Q

• What 4 radiographic findings would elevate your concern for clinically significant LS disease?

A

• LS step sign (sublux)
• Sacral osteochondrosis
• Transitional vertebra
• LS IVD vacuum phenomenon

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23
Q

• List 3 alternatives to standard radiographs that may help with dx LS disease (contrast studies).

A

• Myelography - unlikely helpful, dural sac is dorsal, terminates at different sites per dog
• Epidurography - epidural space contrast, more helpful;
• Discography - contrast into NP; more volume = disc degeneration

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24
Q

• What 2 things can be performed in conjunction with CT to increase sensitivity of ID LS stenosis?

Study These Flashcards
A

• Imaging with hips in extension
• IV contrast -> inflamed tissue will be hyperattenuating

25
• Describe the findings. What are the classic lesions seen on CT.
• Sagittal soft tissue CT image of L7-S1 • Collapse of IV disc space • End plate sclerosis • Vacuum disc phenomenon (arrowhead) • Ventral spondylosis • Ventral subluxation of the sacrum (dotted line) • Elongation of the sacral laminae (arrow) into the caudal aperture of L7 • Can also see: • Bulging of the disc into the canal • Subluxation/osteophytosis of the zygapophyseal joint
26
• What is being indicated by this arrow?
• Osteochondrosis lesion of the dorsal aspect of the sacrum
27
• Describe this image.
• T2W sagittal image of the LS spine. There is decreased signal in the ventral spinal cord with spinal cord compression at the LS joint consistent with degeneration and herniation of the disc. There is compression of the spinal cord on dorsal aspect overlying the LS joint caused by extension of the sacral laminae into the intervertebral space of L7. There is proliferation of the yellow ligament.
28
• What is this arrow indicating?
• T1W sagittal image of the LS spine • Loss of hyperintensity in the L7-S1 intervertebral foramen suggests that the normal hyperintense signal of fat has been replaced with something that is hypointense such as disc material, fibrosis or bony proliferation.
29
• What ideal imaging windows should be used in MRI to classify LS stenosis/LS disease?
• T1 pre and post, help r/o discospondylitis • T2 in sagittal and transverse
30
• What are some (4) drugs that can be considered for medical management?
• NSAIDs • Gabapentin • Amantidine • Opioids
31
• What are the types of surgical procedures to address LS stenosis?
• Dorsal laminectomy • Partial discectomy • Foraminotomy • Removal of the zygapophyseal joint • Distraction and Stabilization= Indicated if zygapophyseal joint is removed or there is instability present • Pins, screws and PMMA or interbody devices
32
• What must be removed sufficiently to allow decompression if disc protrusion is causing compression?
• L7 lamina - caudal ⅔ at LEAST
33
• List 5 surgical treatments for LS disease
• Dorsal laminectomy** • Foraminotomy • Partial discectomy • Dorsal fenestration • Dorsal annulectomy w/nucleus pulpectomy • Zygapophyseal joint removal • distraction/stabilization
34
• When should surgical stabilization of LS space be considered?
• LS subluxation • If destabilized LS enough, ie removal of zygapophyseal joints (bilateral, for sure)
35
• Describe the borders of the dorsal laminectomy at L7-S1.
• Cranial -> caudal ⅔ of the lamina of L7 • Lateral -> medial to zygapophyseal joint • Caudal -> cranial portion of S1 ● Do not remove the joint = destabilization
36
• Describe the technique for dorsal laminectomy and partial discectomy. 524
• Dorsal approach to the LS region • Removal of L7 spinous process with Ruskin or Kerrison rongeurs • Removal of laminae with high speed burr • Remove as far laterally as possible into the yellow ligament under the caudal articular process of L7 • Resect yellow ligament - allows access to intervertebral canal • Remove dural fat to inspect nerves and dural sac • Lateral retraction of cauda equina reveals the disc at L7-S1 • Incise a square into the annulus • Use curette to remove nucleus propulsus • Submit the disc for culture • Fat graft over laminectomy and at annulectomy
37
• What procedure is being performed?
• Partial discectomy • Caudal equina is retracted to the side and a blade is used to make a window in the annulus
38
• What structures are identified in these images?
• L7 nerve root -> runs laterally in the L7 vertebra • Annulus fibrosis of L7-S1 IVD • S1 dorsal root ganglion • Arrowhead = cauda equina and dural sac • Star = IVD • Arrow = intervertebral venous plexus
39
• What is the indication for foraminotomy?
• If the primary problem is caused by nerve impingement in the intervertebral foramen then foraminotomy (widening of the foramen) is recommended
40
• What are the two approaches? Describe the procedures.
• Foraminotomy from laminectomy • Use high speed burr or Love-Kerrison laminectomy rongeurs to widen the foramen from the inside out • Increase visual access by removing the medial aspect of the caudal articular process of L7 • Can use 4mm 30 deg endoscope to visualize • Foraminotomy from lateral approach • Craniolateral approach to the ilium • Remove the gluteal and sartorius from the ilium • Incise the middle gluteal at the level of the cranial ventral iliac spine • Pass finger under to palpate IVD • Draw a line for dorsal spine to alar spine • Drill hole at midpoint of that line
41
• What impedes the view on a lateral approach to L7 foramen?
• Ilium • Iliocostalis lumborum m.
42
• What does this image depict?
• Left sided foraminectomy performed from a lateral approach (note the intact articulation)
43
• What are the 3 goals of distraction and stabilization?
• Bony fusion of L7-S1 • Maintain IVD space • Decrease post-op development of OA
44
• List 3 methods for distracting the LS space temporarily, and maleffect of over-distraction.
• Gelpi • Preplaced screws on pedicles • T-handle distractor in IVD space • *excessive force on L6-7 -> degeneration, protrusion of disc
45
• List 3 sources of bone graft for cancellous bone graft of stabilization procedure
• Wing of ilium • L7 lamina • L7 spinous process
46
• List the stabilization techniques. 527
• Pins/screws PMMA • Pedicle screw rod fixation • Transarticular lag screws • Dorsal Cross pinning • Interbody device can be added to any technique • For pin/screw PMMA where are the screws placed and what should be performed during PMMA placement? • Screw should be placed in the pedicles or body of L7 and S1 • Can be combined with dorsal laminectomy but the cauda equina must be protected when PMMA is solidifying
47
• For lag screws what size should the screw be and how should they be placed?
• Screws should be 25% of the diameter of the articular process • Placed 30-45 deg angle to the sagittal plane
48
• How is dorsal cross pinning performed?
• Pins inserted from spinous process of L7 across the joint to the wing of the ilium • Can be combined with dorsal laminectomy if L7 spinous process intact
49
• What is being shown in this image?
• SynCage • Used to maintain the width of the intervertebral disc after distraction and stabilization • Filled with cancellous bone to promote bony fusion
50
• What is being shown in this image.
• Intervertebral spacer
51
• List 6 potential complications associated with these distraction/stabilization techniques.
• incorrect implant placement w/ trauma to neural structures • implant failure • fx of articular process (typically cd process of L7) • Infection • lack of bony fusion • adjacent segment dz (changes in biomechanics altered forces at L6-7)
52
• Surgical outcome of dogs treated for LS stenosis?
• 77% (14 mo) and 73% (21 mo) good outcome • 79% normal (26 mo post op), 93% improved
53
• What are 3 negative prognostic indicators for surgical intervention?
• *severe neuro signs associated with poorer prognosis (ie, only 50% improved after surgery) • *urinary or fecal incontinence associated with poorer px as well • Duration of urinary (not fecal) incontinence • Military dogs- age was a negative prog indicator
54
• What is the clinical sign associated with poor prognosis?
• Urinary and fecal incontinence • Probability for poor outcome 5.88 times higher for dogs with urinary incontinence > 1 mo • Around what time post-op are propulsive forces in the PL restored on force plate analysis? • 6mo
55
• Recurrence rates in dogs that are normal post op, vs improved post op?
• Recurrence rates 3-54% • 16% for those who were normal • 54% for those that showed some improvement
56
• List 5 methods of stabilizing the LS space and whether they can be done with dorsal laminectomy?
• pins/screws + PMMA • YES with DL • Dorsal cross pinning • NO with DL • Lag screw (cortical) across joint • +/- with DL - if type B, where articular processes are kept intact • SOP system - • assuming NO with the DL • Pedicle screw/rod system • YES with DL
57
* Abnormal EMG findings are expected in what muscle groups in dogs with LS disease?
* Only muscle groups innervated by sciatic nerve * Biceps Femoris, Semis T/M * Fibular = cranial tibia and extensors * Tibial = gastroc, popliteus and flexors
58
• For medical management, what % of dogs improved on standard medical management vs epidural injection of methylprednisone?
• 55% (standard) • 79% (epidural)
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