Thoracolumbar vertebral column Flashcards
(97 cards)
1
Q
Describe the anatomic components of the vertebrae
A
2
Q
What tendon attaches to the accessory process?
A
Tendon of the longissimus lumborum
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)
4
Q
What are the 3 components of the intervertebral disc?
A
Nucleus pulposus, annulus fibrosis, cartilaginous end plate
5
Q
What is the composition of the annulus?
A
Concentric lamellae of collagen
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
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)
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
9
Q
Where do the spinal arteries originate?
A
Intercostal arteries
10
Q
Where does the vertebral venous plexus drain?
A
Azygous
11
Q
What are surgical approach options to the thoracolumbar vertebral column?
A
- Dorsal.
a. Cranial thoracic (T1-T5): trapezious and rhomboideus muscles are retracted, and the nuchal ligament at T1/T2 is preserved (continues as the supraspinous ligament).
b. Thoracolumbar (T6-L6): requires elevation of the multifidus muscle, and transection of the longissimus lumborum muscle on the accessory processes. - Lateral: indicated for lateral fenestration and lateral corpectomy from T10-L5 (see image). Requires blunt dissection through the epaxial musculature.
- Dorsolateral (separation between the multifidus and longissimus musculature). Useful for access to the lateral aspect of T9-L7.
12
Q
Name the following instruments.
A
A, Adson periosteal elevator. B, Freer periosteal elevator. C, Surgairtome Micro100 pneumatic drill
13
Q
What muscle has a thick tendinous attachment to the zygapophyseal joints?
A
Multifidus muscle (deep epaxial muscle)
14
Q
What muscle has a thick tendinous attachment to the accessory processes of T11-L7?
A
Longissimus lumborum (superficial epaxial muscle)
15
Q
What a structure approximates the ventral aspect of the vertebral canal?
A
Accessory process
16
Q
What direction should the spinal nerve, artery and vein be retracted at each intervertebral disc space during fenestration?
A
Cranial
17
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
18
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
19
Q
What are advantages/disadvantages of pediculectomy/mini-hemilaminectomy as compared to hemilaminectomy?
A
Advantages: preservation of the zygapophyseal joint, for pediculectomy (which is mini-hemilaminectomy but over one vertebral body) there is the additional advantage of avoiding the spinal nerve, artery and vein, it is faster, and associated with less hemorrhage.
Disadvantages: decreased exposure of the spinal cord, challenging orientation.
20
Q
What are the different types of dorsal laminectomy procedure?
A
- Funkquist A
- Funkquist B
- 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).
A thoracolumbar dorsolateral laminectomy with osteotomy of the spinous processes has also been reported and results in exposure of 75% of the spinal cord.
21
Q
How accurate is radiography in determining the site of thoracolumbar IVDH?
A
57%.
22
Q
What is vacuum phenomenon?
A
Gas radiolucency within the intervertebral disc space on radiography. Uncommon but highly specific finding for IVDH in one report.
23
Q
What are the two locations for injection of contrast with myelography?
A
Cisterna magna or lumbar subarachnoid space
24
Q
How accurate is myelography for the determination of lateralization of IVDH?
A
55-100% accurate.
25
What are the three basic myelographic patterns based on location of the pathology?
1. Extradural.
2. Intradural-extramedullary.
3. Intramedullary.
26
What is the most common side effect observed with myelography?
Seizures - reported in 10-24% of dogs. Other reported complications include myelopathy, apnea, cardiac arrhythmias, meningitis, hemorrhage, death.
27
What increases the risk of seizures with myelography?
Cisterna magna injection and large breed dogs
28
What is central canal filling?
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
29
What is the appearance of herniated disc material on CT?
Hyperattenuating compared to spinal cord, likely secondary to acute hemorrhage and mineral dense disc material.
30
What is the appearance of extruded disc material on MRI?
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. Contrast enhancement is common on T1W post-contrast images.
31
How does signal hyperintensity on T2W images relate to prognosis of dogs with IVDH?
1. T2W hyperintensity > 3-5 x the length of L2 associated with reduced return to ambulation.
2. T2W hyperintensity >90% of the cross sectional area of the cord associated with poor long term function in ANNPE.
32
Why is myelogram contraindicated in patients with inflammatory CNS disease?
Can cause clinical deterioration.
33
What are the advantages/disadvantages of CSF collection from the cerebellomedullary cistern?
Advantages: easy to collect, free from blood contamination, easy to interpret.
Disadvantages: greater potential for morbidity. May not be altered with more caudal disease processes (due to rostral caudal flow of CSF).
34
Describe the characteristic CSF findings for a dog with thoracolumbar IVDH
Typically only mild pleocytosis. Increases in protein were higher at the subarachnoid lumbar location.
Dogs with higher protein concentrations, RBC count, and NCC had more severe injuries at the time of acquisition.
35
What are medical management options for the treatment of TL IVDH?
1) Enforced rest.
2) Use of analgesics, muscle relaxants, and corticosteroids.
3) Physical rehabilitation.
36
What are the documented success rates of medical management for thoracolumbar IVDH?
Ambulatory: 82-88%
Non-ambulatory: 43-51%
For non-ambulatory dogs surgery is associated with a higher likelihood and faster return to function.
37
Are corticosteroids currently recommended in the medical management of TL disc disease?
No - risk of complications (diarrhea, UTI), worsening quality of life scores, and no change in outcome in the literature.
38
What are surgical options for treatment of TL IVDH?
1. Corpectomy.
2. Hemilaminectomy +/- fenestration.
3. Pediculectomy/mini-hemilaminectomy +/- fenestration.
4. Percutaneous discectomy (may only be effective in patients with normal sensation pre-op).
39
What is the length of a lateral corpectomy?
1/4 the length of each vertebra, centered over the disc just ventral to the intervertebral foramen
40
What are the potential disadvantages of lateral corpectomy?
Vertebral column instability and increased risk for fracture/subluxation.
Advantages are potentially enhanced removal of intervertebral disc material with minimal spinal cord manipulation.
41
What are the success rates reported for dogs undergoing IVDH surgery with intact nociception?
72-100%.
Greater time between onset of non-ambulation and admission, and absence of nociception post-operative may be associated with worse outcomes.
42
What are the rates of return to ambulation reported for dogs undergoing IVDH surgery with absent nociception?
43-62%
Dogs with no return of nociception after 2-weeks have a worse outcome. Timing of surgery and duration of loss of nociception have had varied impacts on outcome (in one study progression to non-ambulatory status in less than an hour was associated with worse prognosis).
Subdural hemorrhage, increased age and body weight, and T2W spinal cord hyperintensity >5 x the length of L2 might be negative prognostic indicators.
43
Aside from the absence of nociception what other factors have been postulated to impact outcome with IVDH?
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 been associated with worse outcomes (22% successful outcome compared to 78%). 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.
44
Does durotomy provide any therapeutic benefit in thoracolumbar IVDH?
No, but may provide some prognostic information if the presence of myelomalacia is observed
45
Can a rhizotomy be performed during treatment of TL IVDH if necessary?
Yes, so long as the nerve root(s) are not part of the lumbar intumescence supplying the femoral or sciatic nerves
46
Does fenestration result in decreased rates of IVDH recurrence?
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.
47
What are potential complications associated with fenestration?
Discospondylitis, pneumothorax, iatrogenic damage to the spinal cord, nerve roots or spinal nerves, vertebral instability.
48
What are potential advantages/disadvantages associated with disc fenestration?
Advantages: may reduce the risk of IVDH recurrence.
Disadvantages: increased operative time, lack of proven efficacy, vertebral instability, risk of wound infection.
49
What materials can be used to prevent laminectomy membrane formation following hemilaminectomy of the TL spine?
Gelfoam or fat graft (care must be taken not too make the graft excessively thick, as this may lead to post-operative compression).
50
What is the reported recurrence rate of IVDH post-operatively in surgically and medically managed cases?
Surgically: Ranges up to 20% with long term follow-up.
Medical: Reported up to 40%.
51
Does the number of radiographically opacified disc spaces increase the risk of recurrence in non-dachshund dog breeds?
Yes, each opacified disc increases the risk by 1.4 times
52
What breed of dog has a higher rate of IVDH recurrence post-op?
Dachshunds
53
What are some reported alternatives to disc fenestration for prophylaxis of IVDH?
1. Laser disc ablation.
2. Chemonucleolysis.
Additional studies are required to determine the efficacies of these techniques.
54
What is the most common location of IVDH in the cat?
2/3 are reported in the caudal lumbar vertebrae.
Prognosis for cats with intact nociception appears good (83% success rates).
55
Describe the nervous supply to the bladder
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.
56
What results in an upper motor neuron bladder?
Loss of transmission of ascending and descending information to and from the brain resulting in a large, firm bladder that is difficult to express
57
What treatments can be considered for an UMN bladder?
Alpha adrenergic antagonists to aid in relaxation of the internal urethral sphincter (prazosin or phenoxybenzamine [prazosin more alpha 1 selective]).
Parasympathamimetics (bethanecol) in cases of concurrent bladder atony. Should only be used after alpha-1-adrenergic antagonists have reached therapeutic levels.
58
What causes a LMN bladder?
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.
59
Is urinary catheterization or manual bladder expression more likely to cause UTI in dogs following IVDH decompression?
Neither is more likely. Risk of UTI is associated with duration rather than technique of bladder emptying.
60
What are predisposing factors for development of UTI in dogs with spinal cord injury?
Sex, incomplete voiding, dexamethasone administration, catheter contamination, pre-existing medical conditions, alkaline urine pH, low urine osmolality.
61
Will dogs with spinal walking regain fecal and urinary continence?
No.
62
Label the following surgical instruments.
63
Describe the most common types of vertebral abnormalities
Hemivertebrae: Wedge shaped vertebra. Cause kyphosis which may increase the risk of IVDH.
Block vertebrae: two fused vertebrae immediately adjacent to one another (failure of vertebral segmentation)
Butterfly vertebrae: sagittal cleft
64
What is spina bifida?
Failure of the neural tube to fuse dorsally with concomitant neural tube malformation (meningocele or meningomyelocele).
65
What are the three classifications of spina bifida?
1. Spina bifida occulta: no externally evident abnormalities.
2. Spina bifida cystica: concurrent existence of a meningocele or meningomyelocele.
3. Spina bifida aperta: lesions that are open or threatening to be open.
66
What is the treatment for spina bifida?
Rarely attempted.
67
What is a pilonidal sinus (dermoid cyst)?
Failure of the skin to completely separate from the neural tube during development. Rhodesian ridgebacks most commonly reported.
Results in a focal tubular structure lined by epithelium and hair follicles. May extend to the dura mater.
68
Where are pilonoidal sinuses most frequently located?
Dorsal midline, cervicothoracic or sacrococcygeal.
69
How is a pilonidal sinus diagnosed?
Fistulograms and cross-sectional imaging (CT/MRI).
Excision of the tract is typically curative.
70
What is an epidermoid cyst (cholesteatoma)?
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.
Complete removal is curative (although more commonly exist intracranially, and few successful reports of removal exist).
71
What is a subarachnoid diverticulum?
Focal accumulations of CSF within the subarachnoid space. Can be congenital or secondary to a spinal cord disorder.
Most commonly occurs in the cranial cervical or caudal thoracic spinal cord regions.
72
What is the most common signalment of patients with subarachnoid diverticula?
Younger, male, Rottweilers and pugs
73
What is the treatment for subarachnoid diverticula?
Corticosteroids and surgery (dorsal laminectomy or hemilaminectomy with incision of the dura and marsupialization).
74
What is myelodysplasia?
Congenital malformation of the spinal cord due to incomplete fusion of the neural tube in the sagittal plane most common in Weimeraners. Results in non-painful T3-L3 myelopathy.
Imaging findings typically normal as changes are microscopic.
No treatment is known.
75
According to Nakamoto 2020 in Vet Surg, was the survival rate higher for patients with progressive myelomalacia treated with hemilaminectomy or extensive hemilaminectomy and durotomy?
According to Jeffrey 2020 in Vet Surg, what was the outcome of extended (four vertebral body) durotomy in deep pain negative dogs with TL IVDH?
According to Takahashni 2020 in Vet Surg, what percentage of deep pain negative dogs with IVDH regained ambulation with decompression and durotomy as compared to decompression alone?
Extensive hemilaminectomy and durotomy
16/26 dogs recovered to walk unaided. Durotomy seemed to improve the outcome of deep pain negative dogs in the case series.
57% with durotomy, 39% without.
Progressive myelomalacia was not observed in any patients in which durotomy was performed.
76
In a study by Woelfel 2021 in Vet Surg, what was rate of recovery for both deep pain positive and negative large breed dogs with IVDH and extensive epidural hemorrhage following surgical decompression? What were 2 risk factors for recovery?
Recovery of ambulation occurred in 77% of deep pain positive dogs, and 38% deep pain negative.
Risk factors associated with recovery were clinical severity, number of vertebrae with signal interruption, and extent of decompression (greater extent = improved outcome)
77
In a study by Tirrito 2020 in JAVMA, what factors were associated with unsatisfactory spinal cord decompression as assessed by post-operative MRI for dogs treated for IVDH? Was satisfactory decompression associated with a greater likelihood of a successful outcome?
In a separate study by Auffret 2024 in VRU, in what percentage of dogs was residual extradural disc material observed on post-operative MRI?
Factors associated with unsatisfactory spinal cord compression included severity of pre-operative neurologic signs and compression, thoracolumbar (rather than cervical) IVDH, and ventral circumferential disc distribution.
Satisfactory decompression was associated with a greater likelihood of a successful outcome as well as lower post-operative neurologic grade and lower mean recovery time.
Compare to a study by Auffret 2024 in VRU, which showed no difference in outcomes based on post-operative residual extradural material or residual spinal cord compression.
Residual extradural material was evident in 100% of post-operative MRIs.
78
In a study by Silva 2023 in JAVMA, was there a difference between the spinal cord to vertebral canal area ratios of the cervical and thoracolumbar regions in French bulldogs?
Yes, the TL spinal cord was relatively larger. This contradicts previous assertions that less severe signs were seen with IVDH in the cervical region due to a relatively larger epidural space at this location.
79
In a study by Martin 2020 in JSAP, did overnight delay of surgery in non-ambulatory dogs with IVDH increase the risk of loss of pain perception?
Yes, patients in which surgery was delayed had an increased risk of loss of pain perception overnight.
Compare this to the findings of Zanoguera 2023 in JSAP, where time between onset of clinical signs/presentation and surgery were not associated with outcome (only surgical duration and Frankel grade at presentation were associated with outcome).
80
In a study by Upchurch 2020 in VCOT, did duration of clinical signs prior to surgery or rate of onset of signs affect clinical outcome following IVDH decompression?
In a study by the same group, Compagnone 2022 in VCOT, was an acute onset of clinical signs associated with a worsened outcome in dogs with IVDH? Was fenestration associated with a faster return to ambulation?
No - preoperative neurologic grade was the main variable that was found to be associated with outcome.
Yes - significant association with both acute onset of clinical signs and worse neurologic grade at presentation and poorer outcomes.
Duration of clinical signs prior to surgery and time of surgery did not correlate with outcome (although patients with more acute onset and more severe neurologic signs tended to be operated on sooner).
Fenestration was associated with a faster return to ambulation.
81
In a study by Kerr 2021 in JSAP, what percentage of French bulldogs undergoing decompressive surgery for TL or cervical IVDH had recurrence of clinical signs at some stage post-operative?
51% (median time of 9 months and 21 days)
82
In a study by Pfund 2022 in JSAP, what percentage of ambulatory dogs with urinary incontinence or tail dysfunction related to lumbar IVDH regained function following surgical treatment?
90% regained fecal continence, 86% urinary continence, and 87% tail function. This included 2/3 dogs with loss of tail nociception.
83
What is the difference between a block vertebra and butterfly vertebra?
A block vertebra represents a failure of segmentation, while a butterfly vertebra represents a failure of fusion.
84
In what proportion of dogs was additional disc material found in the vertebral canal post-fenestration in a study by Harris 2020 in VCOT?
1/3 (or 7/21) dogs. Should re-sweep the vertebral canal following fenestration.
85
In a study by Peschard 2022 in VRU, repeated imaging of the thoralumbar spinal column in dogs with recurrent or ongoing neurologic signs following surgical decompression for IVDH commonly found what?
Extradural material at the spinal surgical site (11/21 cases).
The mean number of days between surgery and second MRI was 335.
86
In a study by Cordle 2023 in VRU, what findings on MRI support the diagnosis of progressive myelomalacia in dogs with clinical signs of disease?
Length of the T2-weighted hyperintensity in the spinal cord and HASTE signal loss.
Dogs with PMM also tended to have shorter compressive lesions suggesting a role of more severe focal pressure in the development of disease.
87
In a study by Bibbiani 2022 in JFMS, was ANNPE, disc protrusion (IVDP), or extrusion (IVDE) the most common type of IVDH in cats? Which spinal cord regions are most commonly affected? Which type of IVDH was associated with spinal hyperasthesia?
ANNPE was the most common, followed by IVDP and then IVDE. ANNPE was more common in females, and IVDE in males.
The mid-to-caudal lumbar and thoracolumbar spinal cord regions were most commonly affected.
IVDE was associated with spinal hyperasthesia, ANNPE was not.
88
In a study by Fowler 2022 in JFMS, what was the most common site for cats with intervertebral disc herniation undergoing surgical decompression? Was grade associated with clinical outcome?
L6-L7 was the most commonly affected site of IVDH, with neurolocalization to L4-S3 in 57% of patients.
Presenting grade was not associated with the clinical outcome at the time of discharge or recheck evaluation. Overall cats had a positive outcome (91% at 2 weeks post-operative).
89
In a study by Gomes 2022 in JFMS, what was the most common physical examination finding in cats with discospondylitis? What bacteria were cultured? What was the outcome?
Spinal hyperasthesia was present in all cases, pyrexia only in 3/17.
Staph and E.coli were cultured in 2 separate cases. The remainder were negative (all cases underwent urine culture with 9/17 having direct tissue culture).
Outcome was excellent in 83% of cats (no cats treated surgically).
90
In a study by Bridges 2022 in JVIM, did the presence of extradural hemorrhage affect the outcome in dogs with IVDH? Which breed of dog was most likely to have epidural hemorrhage?
Yes, dogs with extradural hemorrhage were less likely to be ambulatory at 4-weeks post-operative.
French bulldogs were more likely to have epidural hemorrhage, most frequently affecting the TL spine. Dogs with EH more likely to be acutely affected and non-ambulatory on presentation.
In cases with epidural hemorrhage the length of spinal cord compression was greater, although the degree of compression was less. There was also greater intrinsic spinal cord changes.
91
In a study by Gomes 2022 in JVIM, what were the most common CT changes associated with discospondylitis in dogs?
1) Endplate involvement (87.3%), generally bilateral with erosion and multifocal osteolysis.
2) Periosteal proliferation (73%) and spondylosis (67%).
3) Vertebral body involvement (67%) involving 1/3 of the vertebra (sclerosis) and multifocal osteolysis.
92
In a study by Johnson 2022 in JVIM, what finding on MRI was associated with the chronicity of IVDH in dogs?
The presence of hydromelia was associated with more acute presentation (duration of clinical signs <14 days was 79% and 86% sensitive and specific for predicting the presence of hydromyelia).
93
In a study by McBride 2022 in JVIM, what four factors were associated with the risk of spinal shock?
Decreased risk with increasing weight, increased duration of signs, and decreased pelvic limb tone.
Increased risk with presence of paraplegia.
94
In a study by Amey 2022 in JVIM, what was the 6-month success rate for cats treated surgically v. medically for IVDH?
74% surgical, 65% medical (despite a higher neurologic grade at presentation in surgically treated cats).
Neurologic deficits remained in a high proportion of cases (92% medical, 86% surgical).
Cats suffering trauma were more likely to have a successful outcome.
95
In a study by Mehra 2023 in JVIM, did the administration of omeprazole post-operatively in dogs suffering from IVDH reduce clinically detectable GI complications?
No - short term prophylactic administration did not decrease clinically detectable GI complications.
96
In a study by Van Hoof 2023 in JVIM, what was the most likely bacteria cultured in cases of canine discopondylitis? Were males or female overrepresented? Which site was most commonly affected?
Staphylococcus species were most frequently cultured.
Males were overrepresented.
L7-S1 was the most common site.
Historical trauma was associated with an increased risk of relapse, and corticosteroid use was associated with a greater risk of progressive neurologic dysfunction.
MRI and CT were more accurate at detecting lesions than radiography.
97
Which breed is commonly affected by constrictive myelopathies of the TL region, as described by Wachowiak 2023 in JVIM?
Pugs - may be due to chronic instability, and may contribute to subarachnoid diverticulum formation.
