Ch 32 Thoracolumbar Vertebral column

Question 1

TL IVD anatomy
AF
NP
Cartilage

Answer 1

1. AF: concentric lamellae of collagen. offers biomech support and all multidurectional movement
2. nucleus pulposus: remnant from notocord+ chrondrocyte like cells. hydrated, contains glycoaminoglycans (chondroiton, keratan) + Type IV collagen
3. cartilage ends provide nutrients

longitissimus lumbrum (T11-L7) attaches accessory process
spinal n/vessels lie ventral and cranial to tendon
accessory process ~ level with ventral canal

Question 2

What ligaments help to provide stability to the vertebral column?

Answer 2

Three long ligaments:
- Dorsal and ventral longitudinal ligaments
- Supraspinous ligament

Three short ligaments:
- interspinous
- intertransverse
- yellow ligaments

Intercapital ligaments (T2-T11)

Question 3

spinal biomechnics
what forces does IVD resist? body? joint?
passive stability?
which sites ost common?

Answer 3

• IVD provides majority of biomech stability, espicially for rotational and bending forces
• joint: all forces
• vertebral body: butress
• passive: zygopophyseal joint, muscle tendons, IVD, ligaments
• intercapital lig prob wh reduce disc protusion cranial to T11
• disruption of IVD and articular joint alters biomechnics, worsened by double hemilam and lareh breed.
• ## 50% IVDD @ T12/13 and T13/L1

Question 4

Surgery IVDD
indications
timing (4)
aims

Answer 4

for decompression in apporptiate cases (based on neurolocalisation and predicted pathology)
folowing aporoptiate imaging for sxp planning
validated nuero score allow for improtant prognostic evluation (disucss order of loss…)

timing of sx: may mitigate ongoing injury due to compression, however this is contraversial and conflicting evidence in litaerature
1. acute, rapid and severe may benefit asap (bagley 2005)
2. increased PMM rate if delay (casel 2019)
3. no benefit within 24hr (upchurch 2020)
4. 5% may benefit from progression (Martin 2020)

aims: minimase bone removal to reduce instability

intuitive sooner rather than later

Question 5

What muscles are encountered in a dorsal approach to the cranial thoracic spine (T1-T5) which are not encountered more caudally?

Answer 5

Trapezius
Rhomboideus
Splenius (cranially)
Serratus dorsalis (caudally)

Question 6

Where does the nuchal ligament attach?

Answer 6

Spinous processes of T1 and T2

Question 7

What are the main epaxial muscles encounted on a dorsal approach to the TL spine?

Answer 7

Multifidus
Longissimus lumborum

Question 8

What epaxial muscles are encountered on a lateral approach to the TL spine?

Answer 8

Serratus dorsalis caudalis
Longissimus lumborum
iliocostalis lumborum

Question 9

Which muscles are seperated to allow a dorsolateral approach to the TL spine?

Answer 9

Multifidus and longissimus lumborum

Question 10

What are the anatomic landmarks of a hemilam window?
What parts of the vertebral canal does it allow access to?

Answer 10

Landmarks:
- Ventral accessory process
- Base of spinous process
- Base of articular processes cranially and caudally

Access to ventral, dorsal and lateral canal

Question 11

What is a pediculectomy and mini-hemilam?

use xsectional imaging to dictate approptiate laminectomy sx

Answer 11

Pediculectomy - Removes the pedicle over the body of 1 vertebra, leaving the zygapophyseal joint intact

Mini-hemilam - combined pediculectomy over contingous vertebrae

Faster and pediculectomy avoids the spinal nerve, artery and vein. Decreased exposure
possibly increased risk of disc left behind (huska 2014)

Question 12

endoscopic assissted

druid 2019

Answer 12

MI, thus redcued soft tissue damage
equal/preferred in humans (reduced haemorrhage, faster, reduce complciations, better reovery)

cadaver study in canine

Question 13

What are the three forms for dorsal laminectomy?

alternative to bilateral hemi

Answer 13

Funkquist A - Removal of spinous process, laminae, articular processes and approx half of the dorsal portion of the pedicles

Funkquist B - Leaves the articular processes and pedicles intact

Modified dorsal laminectomy - Removal of spinous process, laminae and caudal articular rpocesses are removed. Medial aspect of pedicles can be undercut to enhance exposure

dorsal, lateral access

Question 14

What is the accuracy of radigraphs to determine the site of the primary IVDH?

no infor re cord compression

Answer 14

51-61%

vacuum sign specific

Question 15

What is the sensitivity of myelography in determining the primary site and lateralisation of IVDH?

Answer 15

Site: 74 - 98%
Lateralisation: 55-100%

Question 16

What prognostic factors can be determined from a myelogram?

Answer 16

Length of intramedullary pattern / length L2 vert ratio on a lateral view:
- Over 5 = 26% chance of recovery
- Less than 5 = 66% chance recovery

Intraparenchymal spinal cord contrast medium - seen in 6/7 dogs with myelomalacia in one study

Question 17

What is the reported rate of posy-myelographic seizures? What are some risk factors

myelopathy, apnea, arrythmia, menigitis, bleed, death

Answer 17

10-21.4%
Risk factors include cisternal myelogram and large body size

Question 18

What is the sensitivty of non-contrast CT for detecting the site and side of IVDH?

Answer 18

Site: 84-100%
Side: 79-94%

MRI has significantly higher sensitivity for site (87% vs79%

Question 19

MRI vs CT

Answer 19

CT allow localisation and planning for majority of cases
> inc sensitivity with typical breed
> <10% require other image (emery 2018)
> myelogram increase sens/sepc
> if not IVDD, then difficult to deterimine dz
> MRI outperforms CT by most measrable charactersistics

MRI pros: see non-mineralised and if severe SCI, provide prognosis
> inc, contrast res thus ST suprerior
> disc ID (protusion, extrusion, ANNPE/HNPE

Question 20

MRI findings

Answer 20

• Hypointense on T1W and T2W
• Non-degenerative disc can be isointense on T1W and hyperintense on T2W
• loss of CSF and fat signal
• contrast can intensify disc signal

100% seinsitive for location/site
superior to detect non-IVDD

T2W hyperintensity >3x L2 length only 20% recvoer VMF (levine 2009)

degree of compression not associated with outcome (penning 2006)

Question 21

What sequences can be used on MRI to help identify an inconspicuous IVDH?

Answer 21

1. T2* can help to identify haemorrhage
2. STIR and FLAIR helpful to identify low volume disc extrusion
3. ultrafast, heavily T2W sequence has appearance of a myelogram
4. Disc material may enhance with gadolinium contrast

Question 22

CT findings

Answer 22

• loss of epidural fat opacity
• cord compression
• mineral density within cord
• hyperattenuation = haemorrhage, disc

Question 23

Tretatment

most studies restrospective, thus limitations > not randomised, diff neuro grading, poor follow up etc
provide useful info, but must be cautious with interpretation

Question 24

What is the reported success rate of conservative management with IVDH?

Answer 24

82 - 88% ambulatory
43 - 51% non-ambulatory

Question 25

medical
stratagies (3)
ambulatory vs non

Answer 25

-rest allow AF to heal/scar
-pain relief and antiinflamm
physio to improve muscle mass

studies report good outcomes for ambulatory dogs, difficutl to compare outcomes due to different medical tx
levine 2007
> 80% ambulatory
> 50% recover with no relapse
> 15-20% Tx fail
> 30% recurrence
> nsaid beneficial, CCS equivolcol

in general, for non-ambul:
- longer reocvery and reduce return to functino when compared to Sx
- no DPP, 7% recovery (davies 1983)
- no new advancements in SCI mgmt with evidence-based imrpvoment

Question 26

What is a lateral corpectomy?
Success of decompression?
Risks?

Answer 26

Creation of a “slot” in the vertebral body, 1/4 the length of the vertebrae

90% successful decompression, deeper slots more successful decompression

Risks: Possible instability and risk of fracture/subluxation

Question 27

What are the improvement rates after corpectomy?

Answer 27

18.7% immediate impovement
52.8% improvement at discharge
64.2% improvement 4 weeks
91.4% ambulatory at 6 months, 74.5% having a normal gait

Question 28

durotomy

A randomized trial comparing durotomy and standard
decompression surgery alone would be ideal but
problematic in practice.

olby ACVIM consensus

Answer 28

TIMING
DPN: current literature does not generally demonstrate improved neurologic outcome in deep pain negative dogs with early surgical intervention, often surgery within 24 h

DPN and PMM: one study found (Castel) an association between delay of decompression beyond 12 h and increased risk PMM, but literature overall lacking

SURGERY Emerging evidence > focal or extensive hemilaminectomy and durotomy might decrease the risk PMM in dogs DPN and
may improve survival in dogs with CS of PMM
2 Japanese retrospective studies reported a 91-100% survival rate with extensive hemi and durotomy, though most remained paralysed, including the FL if affected.

Jeffery: 1 prospective study reported a reduced occurrence of PMM following extended durotomy (4 vertebrae) in G5 dogs

AVCIM consensus suggests that extensive hemilaminectomy with durotomy can be considered for dogs with suspected PMM
however, long-term morbidity (such as spinal instability) and how much surgery require further investigation

Question 29

Effect of durotomy in dogs with thoracolumbar disc
herniation and without deep pain perception in the hind
limbs
Fumitaka Takahashi

Answer 29

retrospective
- increased recovery to ambulate with durotomy
- no DPP, no dogs with durotomy developed PMM
- not prevent progression of PMM
- death 12%

Question 30

Extended durotomy to treat severe spinal cord injury after
acute thoracolumbar disc herniation in dogs
Nick D. Jeffery

Answer 30

the small sample and the lack
of a control group preclude definitive conclusions regarding
the efficacy of durotomy.

Question 31

Outcomes of dogs with progressive myelomalacia treated
with hemilaminectomy or with extensive
hemilaminectomy and durotomy
Yuya Nakamoto

Answer 31

durotomy allow insepction of cord and reduce pressure

Question 32

outcomes
1. normal nociception

most retrospective studies

Answer 32

-most reliable indiciator of prgnosis
- 72-100% recovery (volunrary ambulate and uirnate)
- excellent if ambul
- increased sevrerity ~ increased recovery time
- >90% nonambulatory will reover within 3 months if DPP present (most within 4 weeks) Davies 2022
- mean time to walk 14d

Question 33

2.absent nociception

no test 100% predictive

Answer 33

-ensure conscious
- 43-69% return to ambulate with Sx (Aikawaw 2012, Ruddle 2006)
- if no pain in 2 weeks, prognosis poorer
- recovery time 5-10 week
- MRI lesion prgnostic (5x >L2 Ito 2005, levine 2009)

Question 34

3, timing

Answer 34

contraversial
Martin 7% benefit (g4 turn into 5)
Upchurch no effect
previous studies no bovious diff with duration f CS to decmopression

> disparity, this intuituive to perform sooner

Question 35

4.location

Answer 35

no diff in outcome (ruddle 2006)

Question 36

5.size

Answer 36

larger
slower to recover
l1-l2 common, most type I, > 90% return to function

Question 37

6.type

Answer 37

22% successful outocme with protursion compared to 80% extrusion
older lesions gradually compress causing irrevesible damage to cord

Question 38

recurrence

with or without PF

Answer 38

reported rate of recurrence
0 – 24.4% with PF
2.7 – 41.7% without PF
across multiple studies over the last 50 years

definition of recurrence varies in the literature.
Some studies include only patients with neurologic deficits and confirmed compressive lesions
where as others also include those with any new signs of neck or back pain, so presumed IVDD without proving a disc-based cause

20% within 3 years (mayhew 2004)
40 % medically managed

The number of radiographically opacified IVD increases the risk of recurrence 1.4x in non-Dachshund breeds.

We know that IVDD is a body-wide condition in many affected animals and those that have symptomatic disease at 1 site are at risk for recurrence at another.

Furthermore, multiple studies have shown that almost 90% of thoracolumbar Type I IVDH occur between T11 and L3

So the goal of Prophylactic Fenestration is to creates a window in the anulus fibrosus to partially remove the nucleus pulposus
> thereby reducing or preventing future extrusion of disc material

Question 39

prophylactic fenestration
early vs late

Answer 39

Early recurrences occur within 4 to 6 weeks of surgery and are usually always related to further extrusion at the same site of initial IVDH.
Has a 1-5.8% reported incidence.
Occur before the complete physiologic healing time of disc tissue

Late recurrence is almost always at a new site- 87.5% occur at a disc space adjacent to or one disc away from the initial lesion

Question 40

PF
risk factors

Answer 40

Risk factors identified:
> The presence of degenerate discs on imaging at the time of initial extrusion significantly increases the chances of a late recurrence
> Mayhew: dachshunds at increased risk of recurrence, though this wasn’t supported by a later study by Brisson 2011.
> Recently, Kerrs paper on French bulldogs suggested a 51% rate of recurrence in the breed

Question 41

PF - tehcnique

recent Hall survey > suggested an overall increase in the routine performance of fenestration, with surgeons (55%) and neurologists (82%).

Answer 41

Some or all discs from T11-L4 can be fenestrated – the no. depends of clinician preference and patient factors
L4-5 and L5-6 > due to concern for injury of the nerve roots essential for weight bearing at that location

traditional fenestration a #11 blade is used to create a window in the annulus
a simple incision into the annulus to allow lateral escape of NP is ineffective long-term because the annulus rapidly heals

So, manual fenestration involves removing nuclear material with the use of a dental scraper, curette or similar implements
However, often residual NP is left, especially on the contralateral side of the disc (see picture)

cadaver studies have been performed in attempt to improve the success.
Holmberg study suggested that power fenestration (making a hole in AP larger with burr) improved percentage of disc removed,
Forrtere study suggested even further improvement with an ultrasonic aspirator technique

While these devices augment removal, none shown to besuperior to manual in clinical outcomes.

Question 42

Percutaneous Laser Disc Ablation

Answer 42

Percutaneous Laser Disc Ablation
minimally invasive
fluoroscopy is used to guide percutaneous placement of needles, fine fiberoptic cable is passed into the center of the disk; the laser is activated
low complication rate (<2%)
The Dugat study reported recurrence of clinical signs over 3 years as (20%) dogs suspected
> procedure may be dangerous to the spinal cord if there is rupture of the annulus, and current recommendations 6 weeks or more after any sx

Forterre’s MRI study confirmed that all fenestrated dogs had residual material within the disk
> allowing for potential of reherniation

The effectiveness of fenestration, therefore would appear to be directly related to the skill and experience of the operator

> > > whether removal of more nucleus corresponds to a greater prophylactic benefit has not yet been answered

Question 43

arguments for PF

Answer 43

most common long-term complication after decompressive spinal surgery

Good evidence that that a fenestrated disc is less likely to extrude
Brisson found that its protective, with only 8% of recurrences occurring at a previously fenestrated site.
Multiple studies shown most recurrences occur at a new disk space > 70% in a region that could have been readily fenestrated during the first surgery.

Early recurrence is almost solely due to reherniation of the same disk space
»> radiographic evidence of mineralization at the herniated IVD space support fenestration of the affected disc space at the time of decompressive surgery
»> it is intuitive to consider if there was only low volume found during decompressive surgery.

The reported complications rates appears very low, of >1,000 cases reported in the studies,
complications from fenestration were noted in only 15 cases (0.01%)

Avoids morbidity, costs, and potential choice of euthanasia for dogs affected a second or more
Perhaps especially pertinent in dachshunds and French bulldogs.

Question 44

recurrence rate PF vs no PF

Answer 44

There are lots of studies on outcomes of IVDD, but most have small numbers.
These are the more pertinent large scale studies > as you can see, most are retrospective.
The Necas + Mayhew are non Fenestration studies as a comparison

Brisson 2011: Well- designed prospective trial compared the recurrence rate in dogs that underwent decompressive surgery and were either fenestrated at a single site or multi-disc
There was a substantial reduction in risk of recurrence in the multifenestrated group (7% vs 17%)
odds of recurrence at a nonfenestrated disk space were approximately 11 times the odds of recurrence at a fenestrated disk space

Aikawa study: less that 3% recurrence rate of confirmed cases, and this is the results of ONE surgeon
»> extrusion at non-PF discs was found to be 26.2 times higher than that of PF discs

Dugat laser ablation study > 3.6% recurrence, were confirmed by means of CT or MRI and hemilaminectomy

Question 45

arguments agist PF

Answer 45

increase anaesthetics and surgical times (prolonged recovery, increased infection risk and increased surgery cost)

displacement of disc material into the vertebral (important > where you cant check the vertebral canal– Harris 2020 showed this occurred in of 7/21 cases,
» clinical significance is unknown
spinal cord trauma (worsening of neurologic deficits)
Haemorrhage (including due to laceration of aorta)
soft tissue and nerve root trauma (leading to postoperative pain, scoliosis and abdominal wall weakness)
Difficulty identifying disc spaces for fenestration (including suboptimal removal of disc)
Pneumothorax + Discospondylitis + vertebral subluxation and instability

Fenestration of healthy discs leads to accelerate degeneration within disc and also affects biomechanics,
> Hills biomechanical study revealed that fenestration most significant, single destabilizing factor when compared to hemilaminectomies
>may result in abnormal biomechanical forces being exerted on the disks adjacent to the treated sites, leading to extrusion (so called ASD)

Question 46

PF overtreating?

Routine fenestration means that many more discs and dogs are being subjected to additional surgery than were ever going to have a clinically significant problem with those discs.

If we take Mayhews nonPF outcomes > Hypothetically, because prognosis is good for the 19.2% of dogs that suffer a second episode of IVDD,
performing a second decompressive surgery on only this subgroup of dogs may be preferable to performing unnecessary fenestrations in the other 80.8% that were never destined to have a recurrence.

No evidence indicates that the prognosis is worse after a second hemilaminectomy

Answer 46

Several challenges exist in interpreting the existing literature on fenestration

No studies have prospectively compared recurrence rates for patients with fenestration to those without fenestration

Retrosepctive studies have no controls, no blinding, differences in # + sites of fenestration, the technique, surgeon’s skill level, follow-up time, and sample population

While Brisson prospective study shows reduced recurrence with multi-disc PF, it doesn’t compare to not fenestration at all.

And as I pointed out earlier, the overall incidence of recurrence may not be a low as suggested in the PF studies

Mayhew > the incidence of recurrence without PF combined is 9.1% of 1,184 dogs across several studies , but the true incidence is no known due to these challenges of comparing literature.

The large variation in recurrence number for both groups probably suggests there are multiple factors that influence recurrence and that fenestration is not a perfect solution

Question 47

complications of TL IVDD
intra-op (4)

Answer 47

heamorrhage
iatrogenic damage
wrong site
inadeuate disc removal

Question 48

post-op complications IVDD tL (9)

post-op care

Answer 48

PMM 10% (olby, takahashi 2020)
inadequte decompression
instability
infection 0.6% (dyall)
reperfusion injury
peridural fibrosis
recurrence
ongoing neuro deficits - 20% high grade
urinary incontinence (skytte 2018)
- most reocvery micturition before ambulation (90%)
- G1-4 2-6 days
- G5 14 days

if deteriorate > cosndier reimage

Post op care
- analgesia, recumebency care, pneumonia/regurge
- physio (olby 2005) 5 step protocol, possibly reduce post-op probpems and retunr to function quicker

Question 49

name instruments

Answer 49

From left to right
- Kirby intracapsular lens retractor hook
- Angled nerve hook
- House curette
- Curved dental tartar scraper
- Angled ball probe

Question 50

urinary care

Answer 50

void via expression (only 50% out) vs indwelling or intermittent ucath
q6-8hr: prospective study suggests that duration required to express rather than method associated with UTI

Pelvic nerve (S1-S3)
- Parasympathetic to detrusor muscle
- motor
- urine void (contraction)

Pudendal nerve (S1-S3)
- Somatic innervation
- external urethral sphincter, perineal musculature, anal sphincter and skin of perineum
- urine store: inc tone external sphincter
- urine void: reduce external tone

Hypogastric nerve (L1-L2)
- Sympathetic innervation
- internal urethral sphincter
- detrusor muscle.
- urine storage (b detrusor relax, a sphinctor increased tone
»Inhibits parasympathetic neurons during urine storage.

Question 51

UMN bladder

Answer 51

large, firm, difficutl to express
Tx:
aim to reduce internal sphincter tone
- prazosin (a1 specific, rapid)
- phenoxybenzamine (a1 and a2, may reduce BP)
reeduce external tone (diazepam)

bethanacol if atony

LMN: dt intact hypgastric casuing dtrusir to relax and non-intact pelvic/pudedal reduce sphinctor tone)

Question 52

What are hemivertebrae?
Block vertebrae?
Butterfly vertebrae?

Answer 52

Hemivertebrae
- Incompletely formed, wedge shaped vertebrae resulting from failure of one or more sclerotomes to form during embryogenesis.
- Can prediapose Frenchies to lumbar IVDE and also place at higher risk of myelomalacia

Block Vertebrae
- Fused vertebrae due to failure of vertebral segmentation

Butterfly vertebrae
- A sagittal cleft witihin the vertebral body

Question 53

What are the three forms of spina bifida?

Answer 53

Spina bifida occulta - no external evidence

Spina bifida cystica - concurrent meningocoele, meningomyelocoele or myeloschisis

Spina bifida aperta - open dysraphic/myelodysplastic disorders

Spina bifida is failure of the lamina to fuse dorsally, often associated with other neural tube malformations

Question 54

What is a pilonidal sinus?

Answer 54

A congenital condition wherein the skin failts to completely seperate from the neural tube.
aka Dermoid sinus, Rh. Ridgebacks overrepresented

Question 55

What is an epidermoid cyst?

Answer 55

Incomplete seperation of the neuroectoderm from the ectodermal tissue, trapping viable ectodermal cells within the CNS

Question 56

What is a subarachnoid diverticula?

Answer 56

A focal accumulation of CSF within the arachnoid membrane or subarachnoid space.

Controversy if this causes cord compression and subsequent atrophy or if spinal cord atrophy leave extra space which then fills with CSF

Pugs and Rottweilers overrepresented

Surgical marsupialisation best outcome

Question 57

What is myelodysplasia?

Answer 57

Incomplete or abnormal fusion of the neural tube along the sagittal plant. Aka dysraphism

Weimeraners overrepresented.

Microscopic - no visible on CT myelogram. All dogs will have a bunny-hopping gait

Question 58

Surgical Site Infection Rate after Hemilaminectomy
and Laminectomy in Dogs without Perioperative
Antibiotic Therapy
Barbara A.R. Dyall 2018

Answer 58

retrospectively review the surgical site
infection (SSI) rate in dogs undergoing laminectomies without perioperative antibiotics,
and compare those data with the expected infection rate for clean surgical wounds
in dogs undergoing similar procedures.

Overall, the SSI rate was 0.6%, while the expected SSI rate in clean operative wounds in dogs and cats is 2.0 to 4.8%.

the routine
use of perioperative antibiotic prophylaxis in dogs undergoing laminectomy procedures
should be reconsidered

Question 59

There were no significant associations between administration of prazosin and/or diazepam and length
of hospitalization or urinary continence scores at the time of discharge from the hospital (P > 0.05).

We did find that development of bacteriuria was significantly associated with administration of medication

Question 60

Clinical presentation, magnetic resonance imaging features, and
outcome in 6 cats with lumbar degenerative intervertebral disc
extrusion treated with hemilaminectomy
Hamilton-Bennett

Answer 60

An acute onset and short
duration of progressive clinical signs of myelopathy was the most common presentation

Conclusion: Intervertebral disc extrusion was diagnosed by MRI in all 6 cats, most
commonly at L2-3 and L6-7. Hemilaminectomy resulted in a good to excellent outcome
in 4 of 5 cats.
Clinical significance: Feline IVDE can be diagnosed by MRI and carry a good
prognosis after surgical decompression, although urinary continence may be
delayed despite good pelvic limb voluntary motor function.

Question 61

Clinical presentation, diagnosis, treatment and outcome of spinal epidural empyema in four cats
(2010 to 2016)
S. Guo

Answer 61

Three cats were treated by surgical decompression plus antimicrobial therapy and one cat was treated medically. All cats showed satisfactory improvement following treatment over a follow-up period of 3 months. Spinal epidural empyema is a rare condition but all cats in this series had favourable outcomes.

Question 62

Same-day surgery may reduce the risk of losing pain perception in dogs with thoracolumbar disc extrusion
S. Martin 2020

Answer 62

Retrospective, single centre study on 273 client

Seven of 151 dogs in the early surgery group lost pain perception overnight compared to 15 of 122 in the delayed surgery group

This study suggests that an overnight delay before spinal decompression increases the risk of clinically meaningful deterioration in dogs unable to walk following thoracolumbar disc extrusion.

Question 63

Introduction of Disc Material into the Vertebral
Canal by Fenestration of Thoracolumbar Discs
Following Decompressive Surgery
Georgina Harris 2020

Answer 63

Study Design Twenty-one dogs that underwent hemilaminectomy and disc fenestration

Seven dogs showed the presence of new disc material in the vertebral canal
post fenestration.
This preliminary study shows that additional disc material can be forced into the vertebral
canal by fenestration following decompressive surgery, with a frequency of 7/21.
Conclusion This illustrates the importance of checking the vertebral canal after
fenestration of an extruded intervertebral disc.

Question 64

Minimally invasive spine surgery in dogs: Evaluation
of the safety and feasibility of a thoracolumbar approach
to the spinal cord
Julien Guevar

Answer 64

Study design: Prospective study.
Animals: Six healthy research dogs.

Question 65

Effect of Duration and Onset of Clinical Signs on
Short-Term Outcome of Dogs with Hansen Type I
Thoracolumbar Intervertebral Disc Extrusion
David A. Upchurch 2020

time is continuous, subject to recall bias.

Answer 65

determine if either the rate of onset of clinical
signs or duration from initial clinical signs to surgical decompression affected the
overall quality or duration of recovery in dogs with intervertebral disc extrusion.
Study Design This was a retrospective case series of 131 client owned dogs.

timing of surgery for the dogs in this retrospective
study was decided by the clinicians. As a result, there may
have been a bias

Delay frominitial clinical signs of intervertebral disc extrusion to surgery
is unlikely to affect the ultimate outcome or the length of time for a dog to regain pain
sensation, urinary continence or ambulation. The rate of onset of signs likewise does
not influence these outcomes.

Question 66

Three-dimensionally printed patient-specific drill guides are
a safe and effective method of placing pedicle screws in dogs with thoracolumbar
vertebral malformations.

Question 67

Relationship of preoperative neurologic score with intervals
to regaining micturition and ambulation following surgical
treatment of thoracolumbar disk herniation in dogs
Ditte Skytte

Answer 67

Retrospective case series with nested cohort study
54 dogs weighing < 20 kg (44 lb) that were surgically treated for Hansen
type 1 IVDE
54 dogs weighing < 20 kg (44 lb) that were surgically treated for Hansen
type 1 IVDE

Question 68

Agreement of surgeon’s perception of the effectiveness
of spinal cord decompression with findings
on postoperative magnetic resonance imaging
for dogs surgically treated for intervertebral disk extrusion
Federica Tirrito

Answer 68

Satisfactory (vs unsatisfactory) decompression as assessed
via MRI was associated with a lower postoperative neurologic grade,
greater likelihood of a successful outcome, and lower mean recovery time.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that for dogs surgically treated for IVDE, the surgeon’s
perception of adequate spinal cord decompression may be less reliable than
postoperative MRI findings. Postoperative MRI appeared particularly useful
for dogs with a severe preoperative neurologic status, severe preoperative
spinal cord compression, and thoracolumbar IVDE.

Question 69

Influence of peri-incisional epaxial muscle infiltration with
bupivacaine pre- or post-surgery on opioid administration in dogs
undergoing thoraco-lumbar hemilaminectomy
W.J.M. McFadzean

Answer 69

Thirty dogs undergoing T3-L3 hemilaminectomy were randomly
assigned

Bupivacaine reduced peri-operative opioid administration
and pre-surgical peri-incisional infiltration yielded the greatest benefit.

Question 70

Effect of irrigation technique on the vertebral canal
temperature during thoracolumbar hemilaminectomy
in dogs: An ex vivo study
Dongaonkar 2021

Answer 70

Study Design: Ex vivo study.
Sample Population: Ten canine cadavers.

Lower vertebral canal temperatures (peak and mean) were maintained during
hemilaminectomy with intermittent bolus rather than continuous irrigation.
Clinical Significance: Both intermittent bolus and continuous irrigation are
suitable to prevent elevations in canine vertebral canal temperature during
hemilaminectomy.

Drilling was performed for 15 s
followed by a 10-s pause

Question 71

Outcomes of dogs with progressive myelomalacia treated
with hemilaminectomy or with extensive
hemilaminectomy and durotomy
Yuya Nakamoto

Answer 71

Study design: Retrospective clinical study.
Animals: Twenty-eight client owned dogs that underwent EHLD (n = 10) or
HL alone (n = 18).

The survival rate was higher in the EHLD group (P = .03) compared
with the HL-alone group

Conclusion: EHLD durotomy at the intramedullary hyperintense region on
T2W-MRI improved the survival rate of dogs with PMM compared with dogs
treated with standard HL.

Question 72

Thoracic Vertebral Canal Stenosis Associated with
Vertebral Arch Anomalies in Small Brachycephalic
Screw-Tail Dog Breeds

Question 73

Late onset recurrence of clinical signs after surgery for intervertebral disc extrusion in French bulldogs
S. Kerr 2021

Answer 73

Forty-three (51%) dogs that had decompressive surgery for thoracolumbar (n=29) or cervical (n=14) intervertebral disc extrusion suffered recurrence of signs. The median time between decompressive surgery and recurrence of clinical signs was 9 months and 21 days

Question 74

Transthoracic Vertebral Distraction and Stabilization
in 10 Dogs with Congenital Thoracic Vertebral
Malformations
Mariné 2021

Answer 74

Congenital thoracic vertebral body malformations (CTVBM)
are common findings in screw-tailed brachycephalic breeds
and in pugs.
cause neurological signs due to spinal cord compression,
instability or both. Medicalmanagement of CTVBM has been associatedwith
an unfavourable outcome, leading to the progression
Most described techniques have
used a dorsal approach

VCA was measured as the angle formed between two
lines parallel to the vertebral canal floor of the first cranial
and caudal normal vertebrae.

Seven dogs recovered full function. Nine
dogs improved after surgery compared with preoperative status, recovering ambulation
when lost or achieving normal neurological examination in seven cases. No complications
were reported during the follow-up period (12–50 months).

Question 75

Outcomes and prognostic indicators in 59 paraplegic
medium to large breed dogs with extensive epidural
hemorrhage secondary to thoracolumbar disc extrusion
Christian W. Woelfel

Answer 75

Study design: Retrospective, cohort, descriptive study.
Animals: Fifty-nine client-owned dogs.

Dogs with DEEH can have severe postoperative complications.
Loss of pain perception and increased HASTEi are associated with a
poor outcome, while more extensive decompression improves outcome.

Question 76

Hydrated Nucleus Pulposus Extrusion in Dogs:
Thoracolumbar Compared to Cervical Cases
K. V. Kristiansen 2022

Answer 76

Study Design Retrospective, single-center study.
Results Thirty-six dogs

there was no difference in outcome
between C and TL HNPE or conservative and surgical treatment. Mean follow-up time
was 33 days. All patients were ambulatory at follow-up.

19/36 dogs had conservative treatment, 15/36 dogs had
surgery and 2/36 were euthanatized at the discretion of the
owners. Eleven of 21 TL HNPE were treated surgically versus
4/15 CHNPE (p>0.05). The decision for surgerywas statistically
correlated to the degree of spinal cord compression (p¼0.0075)
but not to the presenting MFS

Question 77

Outcome of thoracolumbar surgical
feline intervertebral disc disease
Kayla M Fowler 2022

Answer 77

Results A total of 35 cats met the inclusion criteria for the study. The most frequently reported clinical sign was
difficulty walking (54.2%). The majority of cats presented with an L4–S3 localization (57%). The most common site
of intervertebral disc herniation (IVDH) was at L6–L7 (34%). The majority of feline patients that received surgery
had a positive outcome at the time of discharge (62.5%; n = 20/32) and at the time of the 2-week recheck (91.3%;
n = 21/23). No association was identified between the age of the patient and the grade of IVDD. No association was
identified between the presenting grade of IVDD and the clinical outcome at the time of discharge or at the time of
recheck evaluation.
Conclusions and relevance Cats undergoing spinal decompressive surgery for thoracolumbar IVDH appear to
have a favorable prognosis independent of the initial presenting grade of IVDD

Question 78

Evaluation of the intervertebral disk, vertebral body,
and spinal cord for changes secondary to
percutaneous laser disk ablation
Irizarry 2022

Laser ablation reduces
the total volume of nucleus pulposus by a thermal ablation
or vaporization effect.

concern was
raised in a previous study regarding effectiveness in
dehydrated and mineralized disks, documenting recurrence
at disk sites that were shown to have complete/
mature mineralization present at the time of PLDA

Answer 78

Most recently, a report identified
recurrence risk for confirmed IVDH to be 3.6%, and
suspected IVDH to be 19.8%, in dogs which recovered
from an initial episode of IVDH and underwent a subsequent
PLDA.9 The effect of PLDA on recurrence of
thoracolumbar IVDH in dogs has been described in two
retrospective reports including 277 and 303 dogs.7,9 Prior
to these publications, a pilot study was performed on
33 dogs to determine the efficacy of PLDA in dogs
referred for surgical fenestration.10 These studies documented
successful outcomes with minimal, short-term
complications associated with the procedure.7,9,10

PLDA appears to be a safe, effective procedure performed
on thoracolumbar disks to reduce recurrence of intervertebral disk herniation
(IVDH) in dogs that previously experienced IVDH, despite the
appearance of visible vertebral endplate lesions and mild diskitis on MRI.

Question 79

Results: Eighteen dogs with caudal lumbar intervertebral disc extrusion causing tail dysfunction, urinary
and/or faecal incontinence were included. Urinary continence was recovered in 12 (86%) of 14
affected dogs, faecal continence recovered in nine (90%) of 10 affected dogs and tail function recovered
in 13 (87%) of 15 affected dogs. Loss of tail nociception was recorded in three dogs on presentation;
two made a full recovery and one showed mild persistent tail paresis.
Clinical Significance: The prognosis for functional recovery of urinary continence, faecal continence and tail
function in ambulatory dogs with caudal lumbar intervertebral disc extrusion following surgical treatment
is good. Larger studies are needed to identify prognostic factors associated with failure of recovery.

Question 80

Thoracic vertebral canal stenosis
in cats: clinical features, diagnostic
imaging findings, treatment and
outcome
Sabrina Gillespie

Answer 80

British Shorthairs and male neutered cats were over-represented
(P <0.05). Median age at presentation was 9 years. All cats were presented for a chronic, progressive, painful,
ambulatory, T3–L3 myelopathy. Five cats were treated conservatively, three surgically and one was euthanased

Question 81

Tube cystostomy is effective for urinary outflow
management in dogs with intervertebral disk extrusion
and ischemic myelopathy cranial to the L3 spinal cord
segment: 61 dogs (2018–2022)
Nash 2023

how compare to U-cath?

Answer 81

61 dogs.
CLINICAL PRESENTATION
Medical records of dogs with IVDE or ischemic myelopathy cranial to the L3
The median number of days from cystostomy tube placement until removal was 19 (range, 3 to 74). Fifteen minor and 6 severe postoperative complications were reported, mainly inadvertent removal (n = 11) and peristomal urine leakage (6).

Tube cystostomy facilitates early hospital discharge and allows at-home, extended urinary management in dogs
.reported as easy to use by owners

positive culture was confirmed in 11 of 13 dogs (85% of dogs tested, 20% of dogs with follow-up data available).

In a previous study,2 11 of 20 (55%) hospitalized
dogs for which results of bacterial culture of initial
urine samples were negative developed catheter-associ-
ated UTIs, and in a separate study,5 8 of 21 (38%) dogs
in a small animal ICU (SAICU) developed catheter-
associated UTIs.

4 of the 39 (10.3%) dogs developed a UTI

Question 82

Accuracy and Safety of Neuronavigation for
Minimally Invasive Stabilization in the
Thoracolumbar Spine Using Polyaxial Screws-
Rod: A Canine Cadaveric Proof of Concept
Julien Guevar1

Answer 82

Significant difference in accuracy
between surgeons was found in the thoracic region but not in the lumbar region.
Accuracy and safety improvement are noted for the thoracic region when procedures
were repeated by the novice.
Conclusion This proof of concept demonstrates that using neuronavigation, minimally
invasive stabilization with polyaxial screws-rod is feasible and safe in a large breed
dog model.

Question 83

Thoracolumbar Intervertebral Disk Extrusion in
Dogs: Do Onset of Clinical Signs, Time of
Surgery, and Neurological Grade Matter?
Krizia Compagnone 2023

Answer 83

Study Design In all, 433 client-owned dogs treated for IVDE between 2016 and 2020
were reviewed

Duration of clinical signs and time of surgery did not correlate with
the time to recovery and return of pain sensation, urinary continence, or ambulation.
Conclusion Dogs presented with severe neurological status and/or rapid onset of
clinical signs were operated on more promptly, but their outcomes were also poorer.
There was no significant evidence for a better outcome when surgery was not delayed.

Question 84

Decompressive laminectomy with vertebral stabilization allows neurologic improvement of most Pekingese dogs with thoracolumbar vertebral instability
Aikawa

low frequency of FGF4 expression

Answer 84

The concept of vertebral instability as the cause of the spinal cord injury has been controversial and sparsely investigated in veterinary medicine

APs contribute up to 30% of the stability of the vertebral column in normal dogs

In a recent report18 on Pug dogs, dynamic myelographic study was used to confirm single or multiple dynamic thoracolumbar spinal cord compressive lesions associated with or without AP anomalies. The decompression and stabilization of these segments resulted in good outcomes.18

Question 85

Clinical signs of bacteriuria in dogs with IVDH Hansen type I may be less clinically apparent, compared to dogs without a neurologic condition. In some cases, clinical signs may be limited to new-onset urinary incontinence. In dogs with IVDH Hanen type I that develop postoperative bacteriuria, delaying antimicrobial treatment until clinical signs developed did not result in adverse consequences or systemic illness.

Question 86

The volume of extruded materials is correlated with neurologic severity in small-breed dogs with type I thoracolumbar intervertebral disk herniation
Yusuke Sakaguchi

In this study, the total volume of the materials that had extruded into the vertebral canal plus the intervertebral space was greater than the volume of the intervertebral disks without herniation according to CT myelographic images. Materials including nucleus pulposus, hemorrhage, and torn annulus could be involved in increasing the volume. There was a weak positive correlation between the volume of the extruded materials at the herniated site and the neurologic severity of type I TL-IVDH by means of the Kendall rank correlation coefficient. We suggest that the volume of extruded materials is at least partly responsible for the presenting neurologic severity in dogs with type I TL-IVDH.

Answer 86

Previous studies have found that the maximal transverse spinal cord compression ratio is not correlated with neurologic severity in dogs with type I TL-IVDH on the basis of MRI images.9,10

Question 87

Prevalence of gastroesophageal reflux in dogs undergoing MRI for a thoracolumbar vertebral column pathology
E. Paran 2023

Answer 87

Fifty percent (95% confidence interval: 45 to 57%) of included dogs had evidence of
gastroesophageal reflux. Reflux was not associated with the individual breed, age, sex, neuter
status or body weight. Brachycephalic dogs did not demonstrate significantly higher rates of reflux compared to non-brachycephalic dogs.

Although brachycephalic dogs did not have a significantly
higher instance of reflux, it is likely that the present study was
underpowered

However, dogs induced
with propofol have been found to show higher incidence of
reflux compared to dogs induced with thiopentone
no increase risk using opiods or GA.

Question 88

The intravenous
administration of a gastroprokinetic (cisapride 1 mg/kg)
associated with an anti-acid
(esomeprazole 1 mg/kg) is reported
to minimise the risk of gastroesophageal reflux and regurgitation
during anaesthesia (Zacuto et al. 2012). However, reflux and
regurgitation can occur even with these drugs and oral anti-acid
(omeprazole 1 mg/kg, in the evening prior and morning of GA)
is recommended to neutralised reflux pH in patients considered
at-risk
(Grubb et al. 2020).

Question 89

Does surgical timing affect the rapidity
of recovery in deep pain-entire nonambulatory
dogs with thoracolumbar
intervertebral disk extrusion?
L. Vicens Zanoguera 2023

Answer 89

151 dogsm were prospectively
collected from three referral hospitals.

All but three dogs,
which were all grade IV at presentation, recovered the ability to ambulate. In both univariable and
multivariable models, only duration of surgery and neurological (Frankel) grade at presentation were
significantly associated with the rapidity of recovery of ambulation.

These results should be evaluated in the context
of a limited range of delay since only 14.5% dogs had a delay ≥6.5 hours

Question 90

Treatment of sacro-coccygeal intervertebral disc extrusion causing tail paresis and faecal incontinence in a dog
C. D. H. Franklin1 and A. K. House

Answer 90

A dorsal laminectomy was performed from the cranial margin of S2 to the caudal margin of Cd1. A large volume of mineralised disc material was removed. The material was confirmed on histopathology to be consistent with extruded nucleus pulposus. The patient regained faecal continence within 3 days of hospital discharge.

Question 91

The frequency at which spontaneous resolution of disc-associated compression occurs in dogs is unknown, because most affected cases either do not undergo cross-sectional imaging or, alternatively, undergo surgical decompression. In this case, there was rapid improvement in neurologic function, but it is unclear if that was a consequence of spontaneous resolution of compression or arose through purely neurologic recovery mechanisms.

Question 92

Follow-up MRI appearance of the surgical site in dogs treated
for thoracolumbar intervertebral disc herniation and showing
ongoing or recurrent neurological symptoms
Peschard 2023

Answer 92

21 dogs, single-center, retrospective, descriptive
study was to describe the MRI characteristics of the surgical site in dogs treated
for thoracolumbar IVDH and presenting for ongoing or recurrent neurological signs

The results of this study supported the use of MRI as a diagnostic modality
for spinal imaging following IVDH surgery, and showed that the presence of extradural
disc material at a spinal surgical site is common along with various vertebral and paravertebral changes.

52% of the study population. It remains
unclear whether this was residual from surgery or newly herniated
IVDM. The imaging evidence of persistent extradural compression of
the spinal cord alongside the history of clinical deterioration or failure
to improve prompted surgical reintervention
Because of the initial good
recovery, the authors speculate that the compressive extradural IVDM
at the surgical site result from a recurrence of disc herniation rather
than material left at the previous surgery, and this happened in 2/3
cases despite IVD fenestration at the time of decompressive surgery

Question 93

The presence, morphology and clinical significance of vertebral body
malformations in an Australian population of French Bulldogs
and Pugs
JD Brown 2021

A new subtype, dorsal
wedge, was observed in 12 cases. The presence, number and subtype
of vertebral malformation were not reliable for predicting
the development of neurological signs across both breeds (Chisquare,
P > 0.05). However, spinal kyphosis >35  calculated via
Cobb angle was associated with Pugs that had neurological
deficits (Chi-square, P = 0.028).

French Bulldogs that have spinal cord disease and CVM are
more likely to have pathology distant to CVM with intervertebral
disc herniation most common.

genetic link between screw tails and CVM in bulldog

Answer 93

Prospective cohort study series.
Materials and methods Forty-nine French Bulldogs and Pugs

Dogs with clinically significant CVM generally present with slowly
progressive neurological deficits within the first year of life.5 However,
many CVM are incidentally encountered on radiographs or
computed tomography (CT).

difficulty in differentiating
between clinically relevant and irrelevant CVM has led to the exploration
of various risk factors that may more reliably predict the
development of neurological clinical signs. These have involved vertebral
malformation scoring systems through the specific breed societies
looking at the number and location of vertebral malformations
along the spinal column, as well as the development of a classification
scheme that categorises vertebral malformation types based on a
human classification system.2,6 Further studies have looked at the
degree of spinal subluxation at areas of vertebral malformations and
the subsequent vertebral canal stenosis, the degree of dorsal angulation
(kyphosis), and lateral angulation (scoliosis) of the spinal
column.1,7

Question 94

Chondrodystrophy is a genetic disorder resulting
from the presence of 1 or more copies of the
fibroblast growth factor 4 retrogene on chromosome
12 (CFA12) referred to as fibroblast growth factor
4 like 2 (FGFL2).1–3

Answer 94

In a retrospective, noncontrolled
study of dogs from 61 breeds and mixed-breed
dogs that underwent surgery to manage IVD disease
(IVDD), the presence of IVD calcification was higher in dogs with 2 copies of FGF4L2 (84.8%) than 1 copy
(63.8%) compared to 0 copies (18.5%).1 However, data
from a prospective, controlled study within a single
breed known to segregate the FGF4L2 retrogene has
been lacking.

Question 95

Relationship between breed, hemivertebra subtype,
and kyphosis in apparently neurologically normal French Bulldogs, English Bulldogs, and Pugs

significance of cobb angle??

Answer 95

Twenty-five (43%) dogs had kyphosis, and 10 (17%) dogs had Cobb angles exceeding 35° (a value associated with neurologic deficits7).

additional research is necessary to determine the clinical importance of specific hemivertebra subtypes and the value of screening programs for specific congenital vertebral body malformations in dogs.

high degree of kyphosis may not be the only risk factor for development of clinical disease, as is suggested by
previously reported findings of high Cobb angles exceeding 35° in French Bulldogs without neurologic deficits.18 Indeed, Cobb angle measurements may not represent all clinically important characteristics of spinal curvature abnormalities.

Question 96

Double-blinded placebo-controlled clinical trial of prophylactic
omeprazole in dogs treated surgically for acute thoracolumbar
intervertebral disc extrusion
Mehra 2023

reported in 15-47% of dogs undergoing surgery for acute TLIVDE

initiated 2 weeks b4??

Answer 96

Animals: Thirty-seven client-owned dogs

was initiated immediately before general anesthesia and continued q12h for a total of 5 days

Conclusions and Clinical Importance: Short-term, prophylactic omeprazole treatment
did not decrease clinically detectable GI complications in dogs with acute TL-IVDE.

Prophylactic PPI use has become widespread among veterinary
neurologists20 because of the high frequency of endoscopically visible
mucosal lesions previously reported1,2 and the perceived multifactorial
risk of GI injury in dogs with TL-IVDE treated surgically

Consistent with this conclusion, previous studies have shown that
prophylactic omeprazole, cimetidine, sucralfate, or misoprostol treatment does not decrease clinical GI complications or mucosal evidence
or progression of GI lesions in dogs

Question 97

Functional Obstruction: Detrusor Urethral Dyssynergy

these animals typically have an otherwise normal neurologic examination

Answer 97

abnormality in the reflex arc that allows the urethral sphincter to relax at the initiation
of detrusor contraction and urination.

The lesion is thought to be in the reticulospinal
tract, Onuf nucleus, or the caudal mesenteric ganglion, and it is possible that the lesion
involves the loss of inhibitory signals to the pudendal and hypogastric nerves

Clinical signs are similar to those of mechanical obstruction.
The animal often postures to urinate and is able to produce a urine stream that
quickly becomes attenuated or stops completely.

Ultrasonography is recommended to assess the ureters and renal pelves.
Additional
diagnostics, including contrast urethrography, urethroscopy, or urodynamic evaluation,
may be necessary to verify the diagnosis

treatment: prazosin, an alpha1adrenergic-specific antagonist with demonstrated
effects on both the internal and external urethral sphincters.
Tamsulosin, which is specific for the alpha1A subtype found in the internal urethral sphincter, has alsobeen successful in these dogs.

Some dogs require additional therapy if the striated muscle is more significantly affected. Benzodiazepines, severe and refractory cases, intermittent sterile catheterization
by the owner at home may be necessary

Prognosis for recovery of normal voiding is good, but most dogs require lifelong
therapy for DUD.