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Neurosurgery > Cervical vertebral column > Flashcards

Cervical vertebral column Flashcards

1
Q

Why is it common for more pronounced motor dysfunction to be evident in the pelvic limbs rather than thoracic with a cervical spinal cord lesion?

A

The descending UMN tracts to the pelvic limbs are more peripherally located

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2
Q

What is central spinal cord syndrome?

A

When motor function is more severely affected in the thoracic rather than the pelvic limbs due to a lesion affecting the central aspect of the spinal cord

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3
Q

Are reduced thoracic limb withdrawal reflexes with normal mentation definitive for localization to C6-T2?

A

No, decreased withdrawal reflexes can sometimes occur with C1-C5 lesions

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4
Q

How fast does neurogenic atrophy occur compared to disuse?

A

7 days for neurogenic, disuse likely to take weeks and is less pronounced

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5
Q

Where do the motor neurons of the phrenic nerve originate?

A

C5-C7 (C7-C5 keeps the diaphragm alive)

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6
Q

Describe the cutaneous dermatomes of the thoracic limb

A
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7
Q

What is nerve root signature?

A

Holding of the thoracic limb in a partially flexed position, consistent with lesions affecting the C6-T2 spinal nerve roots

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8
Q

What is the name of the ventral prominence on the caudal aspect of C1?

A

Ventral tubercle, can be used to locate the C1-C2 joint space

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9
Q

Name the ligamentous attachments to the dens

A

Transverse ligament of the atlas: holds the dens in the ventral aspect of the vertebral foramen

Apical ligament: attaches dens to basiocciptal bone

Alar ligaments: attaches dens to occipital processes. Most important for ventrodorsal shearing forces

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10
Q

What abnormalities may result in AA instability?

A

Atlantoaxial joint hypoplasia or aplasia (46% of dogs), dysplasia (34%), dorsal angulation , absence of transverse ligament and separation of dens

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11
Q

What proportion of dogs with AA instability have a normal dens?

A

24%

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12
Q

How common are gait dysfunctions in dogs with AA subluxation?

A

In up to 94% of dogs

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13
Q

Is tetraplegia common in dogs with AA luxation?

A

No, <10%

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14
Q

What are the landmarks for splint application in AA lux cases?

A

From cranial to the ears and rostral mandible to the cranial thorax and xiphoid. Must immobilize the occipitoatlantoaxial articulation

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15
Q

What is the goal of surgical AA stabilization?

A

Bony ankylosis of the AA joint

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16
Q

Is the ventral or dorsal approach preferred for AA luxation repair?

A

Ventral repair as allows for bony ankylosis. Dorsal approach only resists motion in flexion resulting in persistent joint movement and failure of ankylosis

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17
Q

What is a contraindication for dorsal stabilization of the AA joint?

A

Dorsal deviation of the dens

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18
Q

What are dorsal surgical methods of AA stabilization?

A

Wiring (or suturing in small dogs), cross-pinning, nuchal ligament technique, Kishigami AA tension band

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19
Q

What are the optimal angles for screw placement in ventral AA transarticular screw fixation?

A

40 degrees medial to lateral, and 20 degrees ventral to dorsal

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20
Q

What are the surgical options for ventral AA lux stabilization?

A

Transarticular screws or pins, pins and PMMA, screws and PMMA, ventral plating

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21
Q

What are the reported complication rates for ventral and dorsal AA stabilization?

A

Dorsal: 71%
Ventral: 53%

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22
Q

What are the main surgical complications associated with AA luxation repair?

A

Neurologic deterioration, respiratory compromise, implant migration/breakage, vertebral fracture, recurrent pain

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23
Q

What is the reported rate of implant failure in AA luxation repairs?

A

May be as high as 48% for dorsal and 44% for ventral repairs

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24
Q

Dogs affected less than how many days was associated with greater likelihood of successful AA conservative management?

A

30 days

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25
Q

What is the perioperative mortality rate reported for AA stabilization techniques?

A

4-30%

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26
Q

What was the least successful ventral surgical stabilization method for AA luxation?

A

Use of transarticular pins alone

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27
Q

What risk factors have been identified for dogs undergoing surgical repair of AA luxation?

A

Older patients at the time of onset of clinical signs (>24-months), longer duration of clinical signs (>10 months)

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28
Q

How frequently is the fifth cervical spinal cord segment involved in the brachial plexus?

A

In 24% of dogs

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29
Q

Outside of the CNS what is responsible for providing the myelin sheath?

A

Schwann cell plasma membranes. Schwann cells are separated by nodes of ranvier that aid in nervous conduction

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30
Q

What are the function of the dorsal and ventral spinal nerve roots?

A

Dorsal nerve root is for afferent sensory information, the ventral nerve root is for motor function and autonomic inervation

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31
Q

Describe the supporting connective tissue structures of the nerve.

A

Endoneurium surrounds each axon. Groups of axons are surrounded by perineurium. The epineurium surrounds the entire nerve (not present in nerve roots).

32
Q

What is the most common location of traction injury to the brachial plexus?

A

The intradural portion of the spinal nerve roots due to lack of epineurium (motor nerves most frequently affected)

33
Q

Describe the anatomy of the brachial plexus

A
34
Q

What are the 5 classes of injury after trauma to nerves?

A
  1. Neuropraxia: no damage to structure of nerve.
  2. Axonotmesis: Wallerian degeneration but architecture remains intact.
  3. Neurotmesis: complete nerve disruption but intact perineurium
  4. Neurotmesis: rupture of perineurium
  5. Neurotmesis: nerve completely severed
35
Q

What diagnostics can aid in evaluation of brachial plexus trauma?

A

Electromyography (nerve conduction velocity studies), somatosensory evoked potentials (electrophysiology), ultrasound, MRI

36
Q

What are the different types of brachial plexus avulsion injury?

A
  1. Cranial: C(5)6-C7: Musculocutaneous, subscapular, suprascapular, axillary. Rare. Can still bear weight. Reduced shoulder movement and elbow joint flexion. Atrophy of supraspinatous and infraspinatous
  2. Caudal: C8-T2: Radial, median and ulnar nerves. Cannot extend carpus or elbow due to absence of innervation of triceps brachii. Limb carried in a flexed position as C6-C7 nerves intact. Horner’s syndrome (T1 and caudal) and ipsilateral cutaneous trunci reflex loss (C8-T1) are possible.
  3. Injury to entire plexus: Limb is dragged knuckled on the ground.
37
Q

What are surgical methods of brachial plexus injury repair?

A

Neurotization (transfer of a nerve to a injured nerve, not as reliable as grafting), or nerve rootlet reimplantation

38
Q

What are the widest intervertebral spaces in the cervical vertebral column?

A

C4-C5, C5-C6

39
Q

Is the annulus fibrosus thicker dorsally or ventrally?

A

1.5 to 3 times thicker ventrally

40
Q

Where is the dorsal longitudinal ligament thickest?

A

The cervical vertebral column offering increased protection to herniation

41
Q

Where is the internal vertebral venous plexus largest?

A

Cervical vertebral canal (larger and more lateralized)

42
Q

Is cervical disc herniation more common cranially or caudally?

A

In chondrodystrophic breeds most common cranially. Yorkshire terrier, chihuahua and large breed dogs more commonly affected caudally

43
Q

What is the most common clinical signs associated with cervical IVDH?

A

Neck pain (in up to 90% of dogs).

44
Q

Why is it possible for a dog with neck pain to have evidence of spinal cord deviation but no neurologic signs in the cervical region?

A

The ratio of the vertebral canal to spinal cord diameter is greater in the cervical spine which allows greater cord displacement without compression

45
Q

How frequently is nerve root signature observed in dogs with cervical IVDH?

A

22-50% of dogs

46
Q

Is tetraplegia common in dogs with cervical IVDH?

A

No, only 2-7% of cases. Neurologic deficits are typically more pronounced with caudal lesions.

47
Q

Is neck pain a common clinical feature of cervical ANNPE?

A

No, but neurologic signs are often more severe

48
Q

Why can cervical spinal cord lesions lead to respiratory dysfunction?

A

Paralysis of respiratory muscles and loss of sympathetic innervation leading to bronchoconstriction. Can be treated with mechanical ventilation and bronchodilators (theophylline)

49
Q

What is the most common myelographic finding with cervical IVDH?

A

Deviation of the ventral contrast column. Splitting of the ventral contrast column on lateral view indicates extradural lesion (image pg 463 Tobias)

50
Q

What is a foraminal disc extrusion?

A

Disc extrusion close to or within the intervertebral foramen. Can be missed on myelography and on single midline sagittal MRI view. Need transverse MRI sections for accurate diagnosis

51
Q

What is the appearance of hydrated nucleus pulposus extrusion on MRI?

A

High signal intensity (isointense to CSF) on T2W, low signal intensity on T1W

52
Q

What are the length and width limitations of the ventral slot procedure?

A

Should not be greater than 33% of the length of the vertebral bodies, or 50% of the width (although 33% also preferred)

53
Q

In what size dog should cervical fenestration not be performed?

A

> 30 kg

54
Q

How much of the annulus fibrosis should be removed in cervical fenestration?

A

1/3 to 1/2

55
Q

What factors may be associated with an increased risk of post-operative hypoventilation?

A

Lesions between C2-C4, and dorsal laminectomy surgery

56
Q

What are potential surgical complications associated with ventral slot surgery

A

Respiratory compromise, cardiac dysrhythmias (stimulation of vagosympathetic trunk, disruption of descending UMN tracts to the sympathetic nervous system), blood loss, neurologic deterioration, seroma, vertebral subluxation (8% of cases)

57
Q

What are some potential prognostic factors affecting outcome with cervical spine decompressive surgery?

A

Site of IVDH: worse prognosis with more caudal lesions. May represent cervical spondylomyelopathy which could require concurrent stabilization.

Factors with mixed reports as to whether prognostics:
Duration of clinical signs (not found to be prognostic, although dogs that were not walking at 2 wks post-operative at greater risk of non-recovery), severity of clinical signs (mixed, but not generally considered a significant predictor)

58
Q

What are the two recognized types of cervical spondylomyelopathy?

A

Disc associated: large breed dogs (Doberman)
Osseous associated: Giant breed dogs

59
Q

Why is cervical spondylomyelopathy less common in small breed dogs?

A

They have a proportionally larger vertebral foramen. Dobermans have a funnel shaped foramen

60
Q

What are the three factors that lead to disc associated cervical spondylomyelopathy?

A
  1. Vertebral canal stenosis
  2. High levels of torsion in the caudal cervical spine
  3. Large volume intervertebral discs
61
Q

What is the pathophysiology of osseous associated cervical spondylomyelopathy?

A

Proliferation of the lamina, articular processes, or articular processes and pedicles cause varying degrees of vertebral foramen stenosis. This is through a combination of malformation and osteoarthritic changes.

62
Q

Are single site or multiple site lesions more common in large or giant breed dogs with cervical spondylomyelopathy?

A

Giant: 20% had single lesion, compared to 50% of large breed

63
Q

What is the most common location for compression in cervical spondylomyelopathy?

A

C6-C7 for both osseous and disc, followed by C5-C6 (disc), or C5-C6/C4-C5 (osseous)

64
Q

How is cervical spondylomyelopathy a dynamic disease?

A

Extension of the neck leads to narrowing of the vertebral foramen by 16.5% compared to normal. This worsens compression in any direction

65
Q

What is the most common clinical finding in patients with cervical spondylomyelopathy?

A

Proprioceptive ataxia

66
Q

What surgical treatment options are available for disc associated cervical spondylomyelopathy?

A

Static lesions: Ventral slot or cone ventral slot
Dynamic lesions: distraction stabilization techniques such as PMMA plug or pins/screws embedded in PMMA. Continuous dorsal laminectomy also an alternative.

67
Q

What surgical treatment options are available for osseous associated cervical spondylomyelopathy?

A

Generally considered a static disease (although all cervical spondylomyelopathy cases have some degree of dynamic component). Due to primarily static nature decompressive surgeries are prioritized: dorsal laminectomy. Ventral distraction/stabilization with PMMA plug was thought to potentially reduce osseous degeneration/proliferation but there is no evidence of this

68
Q

In the inverted cone ventral slot what is the width at the ventral vertebral body limited to?

A

20% of the vertebral body

69
Q

What is the major problem with dorsal laminectomy procedures in the treatment of cervical spondylomyelopathy?

A

High morbidity rate (65-75% of dogs are worse post-operatively) which can be challenging to manage in large breed patients

70
Q

What angle should be used for pin placement in the cranial and caudal vertebral bodies when using pins and PMMA for stabilization of cervical spondylomyelopathy?

A

35 degrees dorsolateral, with increase to 45 degrees at C7

71
Q

List direct decompressive surgical techniques described for the treatment of cervical spondylomyelopathy?

A

Ventral slot, inverted cone ventral slot, dorsal laminectomy, cervical hemilaminectomy

72
Q

List indirect decompression (distraction stabilization) surgical techniques described for the treatment of cervical spondylomyelopathy?

A

Pins and PMMA, PMMA plug, locking plates

73
Q

What are some complications associated with treatment of cervical spondylomyelopathy?

A

Postoperative neurologic deterioration, vertebral foramen or transverse foramen implant penetration, domino effect, laminectomy membrane, implant failure, collapse of intervertebral foramina, insufficient decompression

74
Q

What is the rate of domino effect following surgery for cervical spondylomyelopathy?

A

20% - appears more frequent following distraction stabilization techniques

75
Q

What is the recurrence rate following surgical treatment of cervical spondylomyelopathy?

A

24%

76
Q

What are extradural synovial cysts?

A

Cysts that originate from the zygapophyseal joint. Can be divided into synovial and ganglion cysts. Can occur anywhere throughout the vertebral column. In the cervical region may be associated with osseous cervical spondylomyelopathy

Neurosurgery (8 decks)

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