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Neurosurgery > Thoracolumbar vertebral column > Flashcards

Thoracolumbar vertebral column Flashcards

1
Q

Describe the anatomic components of the vertebrae

A
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2
Q

What tendon attaches to the accessory process?

A

Tendon of the longissimus lumborum

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3
Q

What are the anticlinal vertebrae?

A

The thoracic vertebrae in which the dorsal spinous processes switch from a caudal to a cranial orientation (T11)

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4
Q

What are the 3 components of the intervertebral disc?

A

Nucleus pulposus, annulus fibrosis, cartilaginous end plate

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5
Q

What is the composition of the annulus?

A

Concentric lamellae of collagen

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6
Q

What is the composition of the nucleus pulposus?

A

Well hydrated, contains a mixture of glycosaminoglycans (chondroitin sulfate and keratin sulfate) and a dispersed matrix of type IV collagen

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7
Q

What are the three long ligaments and three short ligaments of the thoracic vertebral column?

A

Long ligaments: supraspinous, dorsal and ventral longitudinal.
Short ligaments: yellow ligament, interspinous, intertransverse
Additional ligament in thoracic vertebrae: intercapital (T2-T11)

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8
Q

Why is IVDH postulated to be less frequent cranial to T11?

A

Presence of the intercapital ligament ventral to the dorsal longitudinal ligament

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9
Q

Where do the spinal arteries originate?

A

Intercostal arteries

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10
Q

Where does the vertebral venous plexus drain?

A

Azygous

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11
Q

What muscle has a thick tendinous attachment to the zygapophyseal joints?

A

Multifidus muscle (deep epaxial muscle)

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12
Q

What muscle has a thick tendinous attachment to the accessory processes of T11-L7?

A

Longissimus lumborum (superficial epaxial muscle)

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13
Q

What a structure approximates the ventral aspect of the vertebral canal?

A

Accessory process

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14
Q

What are the three major portions of the vertebral column that provide stability?

A

Vertebral body: buttresses against axial loading and resists bending.
Articular processes: resist all forces.
Disc: Lateral bending and rotation

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15
Q

When should additional vertebral stabilization be considered following surgery?

A

Compromise of two or more of the stabilizing components of the vertebra (disc, body, joint), particularly bilaterally, traumatically or in a large breed dog

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16
Q

What are the different types of dorsal laminectomy procedure?

A

Funkquist A, B, and modified dorsal laminectomy (this is similar to the Funkquist A but the pedicles are undercut rather than removed and the cranial articular joints are left intact)

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17
Q

What are the two locations for injection of contrast with myelography?

A

Cisterna magna or lumbar subarachnoid space

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18
Q

What is the most common side effect observed with myelography?

A

Seizures - reported in 10-24% of dogs. Other reported complications include myelopathy, apnea, cardiac arrhythmias, meningitis, hemorrhage, death

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19
Q

What increases the risk of seizures with myelography?

A

Cisterna magna injection and large breed dogs

20
Q

What is central canal filling?

A

Filling of the central spinal cord with contrast following myelogram. Can result from inadvertent spinal cord penetration, contrast leakage, or communication between conus medullaris and subarachnoid space. Doesn’t impede diagnosis but may temporarily worsen clinical signs

21
Q

What is the appearance of extruded disc material on MRI?

A

Normally hypointense on both T1 and T2W images. If hydrated (non-degenerative) can be hyperintense on T2 and isointense on T1 images. Can use STIR, FLAIR or T2* sequences to better delineate

22
Q

Describe the characteristic CSF findings for a dog with thoracolumbar IVDH

A
23
Q

What are the documented success rates of medical management for thoracolumbar IVDH?

A

Ambulatory: 82-88%
Non-ambulatory: 43-51%

24
Q

Are corticosteroids currently recommended in the medical management of TL disc disease?

A

No - risk of complications, worsening quality of life scores, and no change in outcome in the literature

25
Q

What is the length of a lateral corpectomy?

A

1/4 the length of each vertebra, centered over the disc just ventral to the intervertebral foramen

26
Q

What are the potential disadvantages of lateral corpectomy?

A

Vertebral column instability and increased risk for fracture/subluxation

27
Q

What are the success rates reported for dogs undergoing IVDH surgery with intact nociception?

A

72-100%

28
Q

What are the rates of return to ambulation reported for dogs undergoing IVDH surgery with absent nociception?

A

43-62%

29
Q

What length of spinal cord swelling observed on MRI or myelography is associated with a negative prognosis in dogs with IVDH?

A

Swelling that is 5 times or greater than the length of L2

30
Q

Aside from the absence of nociception what other factors have been postulated to impact outcome with IVDH?

A
  1. Location - originally thought that more caudal locations were worse, but there is no evidence for this.
  2. Weight - may have prolonged return to ambulation.
  3. Nucleus pulposus extrusion vs annulus protrusion - treatment of annulus protrusion has typically be associated with worse outcomes. These dogs are often less severely affected, are older, and have a longer duration of clinical signs. Use of hemilaminectomy combined with stabilization has been investigated and may lead to improved outcomes.
31
Q

Does durotomy provide any therapeutic benefit in thoracolumbar IVDH?

A

No, but may provide some prognostic information if the presence of myelomalacia is observed

32
Q

Can a rhizotomy be performed during treatment of TL IVDH if necessary?

A

Yes, so long as the nerve root(s) are not part of the lumbar intumescence supplying the femoral or sciatic nerves

33
Q

Does fenestration result in decreased rates of IVDH recurrence?

A

Mixed reports and remains controversial. Large retrospective study of 255 dogs found that recurrence at sites of fenestration was decreased but there was no overall decrease in recurrence rates.

34
Q

What is the reported recurrence rate of IVDH post-operatively in surgically and medically managed cases?

A

Surgically: Ranges up to 20% with long term follow-up.
Medial: Reported up to 40%

35
Q

Does the number of radiographically opacified disc spaces increase the risk of recurrence in non-dachshund dog breeds?

A

Yes, each opacified disc increases the risk by 1.4 times

36
Q

What breed of dog has a higher rate of IVDH recurrence post-op?

A

Dachshunds

37
Q

What is the most common location of IVDH in the cat?

A

2/3 are reported in the caudal lumbar vertebrae

38
Q

Describe the nervous supply to the bladder

A

Hypogastric: L1-L2: sympathetic innervation. B-receptors in the bladder wall lead to bladder relaxation, alpha receptors at the internal urethral sphincter lead to contraction.

Pelvic: S1-S3: parasympathetic innervation. Cholinergic stimulation is caused by stretch receptors in the bladder wall. This inhibits sympathetic innervation (at the pelvic plexus) to the bladder and results in detrusor contraction and decreased internal urethral sphincter tone.

Pudendal: S1-S3: somatic innervation to the external urethral sphincter (periurethral striated muscle), perineum, and anal sphincter. Inhibited during reflex micturition.

39
Q

What results in an upper motor neuron bladder?

A

Loss of transmission of ascending and descending information to and from the brain resulting in a large, firm bladder that is difficult to express

40
Q

What treatments can be considered for an UMN bladder?

A

Alpha adrenergic agonists to aid in relaxation of the internal urethral sphincter (prazosin or phenoxybenzamine [prazosin more alpha 1 selective]).
Parasympathamimetics (bethanecol)

41
Q

What causes a LMN bladder?

A

Injury to the sacral spinal cord segments or the pudendal or pelvic nerves results in loss of detrusor and external urethral sphincter tone. This causes a large flaccid bladder that is easy to express. Can occur with lesions up to L2-L3.

42
Q

Describe the most common types of vertebral abnormalities

A

Hemivertebrae: Wedge shaped vertebra
Block vertebrae: two fused vertebrae immediately adjacent to one another (failure of vertebral segmentation)
Butterfly vertebrae: sagittal cleft

43
Q

What are the three classifications of spina bifida?

A

Spina bifida occulta, cystica and aperta. It is failure of the neural tube to fuse dorsally with concomitant neural tube malformation (meningocele or meningomyelocele).

44
Q

What is a pilonidal sinus (dermoid cyst)?

A

Failure of the skin to completely separate from the neural tube during development. Rhodesian ridgebacks most commonly reported.

45
Q

What is an epidermoid cyst?

A

Incomplete separation of the neuroectoderm from the ectodermal tissue, which entraps viable ectodermal cells in the CNS. Lined by keratinizing stratified squamous epithelium. Results in expanding cyst filled with keratinaceous material.

46
Q

What is the most common signalment of patients with subarachnoid diverticula?

A

Younger, male, Rottweilers and pugs

47
Q

What is myelodysplasia?

A

Incomplete fusion of the neural tube in the sagittal plane most common in Weimeraners. Results in non-painful T3-L3 myelopathy

Neurosurgery (8 decks)

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