Intervertebral Disc Disease

Question 1

where can disc herniation occur?

Answer 1

any spinal cord segment!
T3-L3 most common!

but also
C1-C5
C6-T2
L4-S1
S1-S3
caudal segments

anywhere!!

Question 2

describe the intervertebral disc

Answer 2

1. interposed between adjacent vertebral bodies
   -not between C1-C2, not in the fused sacrum so L7-S1 is the last one we care about even though the tail does have
2. nucleus pulposus in center: water, proteoglycans, type II collagen
   -health disc is 80% water
3. annulus fibrosis outside: tough fibrous rings
   -thicker ventrally so often herniate dorsally up to spinal cord

Question 3

describe the disease of IVDD

Answer 3

1. IVD degeneration
2. IVDD: disease
3. IVDH: herniation!

Question 4

describe Hansen type I IVD degeneration

Answer 4

major changes to nucleus
-loss of proteoglycans and water +/- calcification in young dogs
-annulus weakens and leas to EXTRUSION: nuclear material in vertebral canal via tear in annulus

Question 5

describe Hansen type II IVD degeneration

Answer 5

major changes to annulus result in PROtrusion; dorsal displacement of annulus and nucleus

-more common in older larger dogs

Question 6

describe ANNPE

Answer 6

acute non-compressive nucleus pulposus EXtrusion

contusion only

Question 7

why do hansen type I IVDH happen?

Answer 7

genetically driven degeneration of disc!!

-young or middle aged: degen begins at 6 months in dachshunds

-certain breeds overrepresented: chondrodystophic!

-NOT because of mechanical forces of long backs an short legs; nothing can be done to prevent if it’s destined to happen

Question 8

how long does it take for the annulus to heal/fibrose?

Answer 8

4-6 weeks! need to rest for at least that long to prevent further degeneration!!

“put them in a box”

Question 9

describe the common signalment for IVDD type I

Answer 9

age
-90% degen by 2 years
-IVDH 2-6 years (peak 4-5)
-not puppies
-less common in older dogs

breed:
-chondrodystrophic
-possible but less common in other breeds (pit bull) but def no the young large breed!

Question 10

describe the common history of type I IVDH

Answer 10

1. acute: hours to days; sudden tear in annulus causes extrusion of nucleus and compression of spinal cord
2. typically progressive: continued damage to cord and possibility for continued extrusion
3. typically painful due to compression of meninges/nerve
4. can be ANY neuroanatomic localization
   -T3-L3 85% of cases
   -T10-L2 most common of those: no intercapital ligaments, high motion, stable to unstable junction

Question 11

describe exam findings of type I IVDH

Answer 11

1. T10-L2 most common so typically have T3-L3 findings
   -hind limb weakness or paralysis with normal to increased reflexes
2. can use cut trunci cut off and pain to further localize
   -pain is NOT a localization
3. signs will range in severity depending on severity of compression
   -proprioceptive ataxia first
   -voluntary motor control goes next
   -then loss of sensation/nociception last
   -based on fiber size! regain in inverse order

Question 12

what is nociception?

Answer 12

1. conscious perception of noxious stimulus
2. a BILATERAL MULTISYNAPTIC pathway!!
   loss requires functional transection of spinal cord!!!
3. MUST look for patient response NOT JUST withdrawal of limb
4. NEVER need to check for sensation in a patient with voluntary motor!! nociception lost after lose motor so should be inact, no need to pinch the puppy

Question 13

describe radiographs to test for IVDH

Answer 13

1. only provide EVIDENCE of disc disease
2. supports a presumptive diagnosis, but not definitive
3. narrow IVD space
4. narrow IV foramen
5. narrow articular facet joint
6. if you’re lucky: see mineralized IVD or mineralized material in plane of vertebral canal over IVD space
7. finding any of these does not mean that those are the reason why the dog can’t walk! just support a diagnosis

not wrong to take in any dog with myelopathy or painful neck or back!

Question 14

describe MRI to make a definitive diagnosis of IVDH

Answer 14

1. dehydrated dark grey discs or even black if mineralized; just means disc degeneration, not spinal cord compression though
2. herniated disc! black spot in spinal cord

Question 15

describe CT to diagnose IVDH

Answer 15

1. only for mineralized disc
2. does not work for all cases
3. cannot visualize spinal cord
   -rarely used

Question 16

describe myelogram to diagnose IVDH

Answer 16

1. rarely used anymore/outdated
2. inject contrast into subarachnoid space to see where lose = compression
3. cannot visualize spinal cord

Question 17

when is type I disc herniation a good presumptive diagnsosis?

Answer 17

signalment: young to middle aged chondrodysplastic dog

history: acute onset, progressive

exam findings: any localization and any severity!
-T3-L3 most common
-pain on exam common

diagnostic findings: evidence of disc disease on rads; if not see, don’t take off list, might not always see!

(MRI would be definitive)

Question 18

when is type I IVDH NOT a good presumptive diagnosis?

Answer 18

signalment: 6mo dachshund (too young), 1 year old great dane (wrong breed)

history: 3 month progressive history; possible in the correct breed but unlikely

exam findings: cranial thoracic cutaneous trunci cutoff

Question 19

what are the 2 categories of treatment of type I IVDH

Answer 19

1. conservative:
   -exercise restriction
   -medication
2. surgical: hemilaminectomy to removed compressive disc

Question 20

define a successful outcome post IVDH treatment

Answer 20

1. able to walk: should see improvement every two weeks in reverse order of how they lost it
2. pain free on no pain meds
3. urinary and fecal continence

Question 21

what is the biggest factor in choosing treatment for type I IVDH?

Answer 21

severity and prognosis!

1. pain only: 95% success of both pain management and surgery; choose meds is okay
2. ambulatory paraparesis and GP ataxia: same as pain free
3. non-ambulatory paraparesis:
   -80% success with medical (not bad, but 2/10 won’t walk again so)
   -95% success with surgery- choose surgery if you can
4. paraplegia (loss of all voluntary motor):
   -60% success with med mgmt- not great
   -90% success with surgery- choose surgery if you can
5. paraplegia absent sensation
   -<5% success with med mgmt
   -50% success with surgery
   -time matters!! but a mystery in real life of when lost sensation
   <24 hrs: surgery is 50% successful
   24-48 hrs: unsure
   >48 hrs: <10% success with surgery

as soon as you can’t walk you are now a surgical candidate! but if money is an issue you don’t have to jump straight to euth, always at least try medical management!!

Question 22

describe time to recovery with medical or surgical management

Answer 22

1. medical: 6 weeks
2. surgical: less than 2 weeks and a more complete recovery

Question 23

describe recurrence of IVDH type I for both types of treatment?

Answer 23

conservative: 50%
-25% fail medical management and progress to where they need surgery
surgical: 10%

Question 24

when to refer with type I IVDH? (4)

Answer 24

cannot refer too early but can refer to late!!

when to refer:
1. acute and severe (even if still ambulatory)
-progressing fast
2. non-ambulatory!!!
3. french bulldog!!
4. not responding to medical management

Question 25

describe exercise restriction

Answer 25

1. STRICT cage rest for 4-6 weeks to allow fibrosis of torn annulus and prevent herniation of more disc material -most owners "over it" by 4 weeks 2. followed by gradual return to exercise

Question 26

describe anti-inflammatory medical managment

Answer 26

corticosteroids versus NSAIDs -no consensus, contact a specialist, just DONT USE TOGETHER 1. prednisone 0.5 mg/kg/day 2. dexamethasone 0.05-0.1 mg/kg/day: not recommended due to severe GI side effects (injectable)

Question 27

describe pain medication management

Answer 27

1. gabapentin (neurontin) 10 mg/kg BID-TID +/- amandatine 2-5 mg/kg once daily

Question 28

describe follow-up from conservative treatment

Answer 28

when recheck? -critical time points: it takes 2 weeks to see improvement; good if dog is walking -tell them you need to see them ASAP if dog stops walking!! -if rapid progression to plegic: recheck in 1-2 days to see if come up with money once lose sensation seek emergency care: when stops walking! on recheck: looking for orderly return to function

Question 29

describe spinal shock phenomenon (6) (another presentation of disc disease)

Answer 29

1. peracute/acute onset 2. severe T3-L3 lesion: paraplegia/almost paraplegia; is an asymmetrical disease even though commonly affects both pelvic limbs! the worst side is thew one with shock 3. immediately LMN caudal to the lesion -no anal tone/perineal reflex -decreased muscle tone -no patellar reflex -no withdrawal reflex 4. spontaneously resolves -perineal normal within minutes -patellar normal within hours -muscle tone and withdrawal can take days to weeks to normalize 5. look for other signs of T3-L3: -cutaneous trunci cut off -pain (to convince yourself is T3-L3) can't be paraplegic due to L6-S1 bc femoral nerve still flexes hips 6. localization: T3-L3 with spinal shock -T3-L3 pain and/or cutaneous trunci cut off -normal patellar reflexes -decreased muscle tone pelvic limbs -decreased withdrawal pelvic limbs

Question 30

describe nerve root signature (4) (another presentation of disc dog)

Answer 30

1. in thoracic (more common) or pelvic limbs 2. lameness (very lame) without orthopedic cause 3. may be non weight bearing 4. typically can decide based on exam without imaging -can't find any reason on ortho exam for why so lame

Question 31

describe ascending descending myelomalacia/myelomalacia (6)

Answer 31

1. hemorrhagic necrosis and liquefaction of spinal cord -unknown inciting cause/pathophysiology 2. occurs secondary to type I IVDH (rare report after trauma) 3. ONLY in dogs with absent sensation/nociception (warn owners to look for signs if doing no sx) -33% french bulldogs -10% all other breeds 4. clinical signs: (ascending and descending usually both happen but might be at different rates) -ascending: 1. cutaneous trunci ascends and eventually becomes absent 2. loss of abdominal muscle tone 3. thoracic limbs become weak (seen as lay them on side and too weak to right themselves as first sign) 4. hypoventilation (abdominal breathing not diaphragmatic) -descending: 1. pelvic limbs become LMN 2. loss of anal tone and perineal reflex 3. loss of tail tone 5. +/- fever and painful (may not really see clinically, literature just says) 6. irreversible!! euthanasia is necessary!!!

Question 32

describe schiff-sherrington phenomenon (another presentation of disc disease) - FYI Barber said she won't ask a test question on it

Answer 32

1. severe T3-L3 lesions (paraplegia) to border cells (lumbar spinal cord) that normally provide inhibition to thoracic limb extensor tone; resulting in rigid extension of thoracic limbs 2. could be from pain 3. does not change prognosis (just a fun gee whiz)

Question 33

describe CERVICAL type I disc herniation signalment

Answer 33

1. 15% of disc herniation cases 2. chondrodysplastic most common -dachshunds!! french bulldogs, toy poodle, cocker spaniel, beagles mostly 3. large breeds also: labs, rotties, dobies, dalmations 4. occurs most common between 4-8 years old

Question 34

describe CERVICAL type I disc herniation exam findings

Answer 34

1. pain ONLY is the most common presentation! -nerve root signature is also more common 2. only 1/3 will be non-ambulatory (more room up there so can compress for pain without taking away walking ability) 3. often asymmetrical thanks to the dorsal longitudinal ligament

Question 35

describe CERVICAL type I disc herniation diagnostics

Answer 35

1. rads: may be normal, but still a good idea with severe pain and large breed to rule out neoplasia 2. MRI!!!!

Question 36

describe CERVICAL type I disc herniation treatment and prognosis

Answer 36

treatment: 1. conservative management is same as for TL type I IVDH -less likely to respond; very hard to manage pain!! -50-85% recovery -33% recurrence 2. ventral slot: >95% recovery prognosis: 1. pain, mild paresis: -medical mgmt: 50-85% -sx: >85% 2. non-ambulatory paresis -medical: unknown -sx: >95% 3. recurrence -medical: 33% -sx: 10-33%

Question 37

describe Hansen type II IVDH (will come up as a test question as a differential) (5)

Answer 37

1. non-chondrodystrophic large breeds 2. older (>6-8 years) 3. chronically progressive (several month history) 4. +/- painful 5. prognosis is not as good as with type I -71% treated with sx have clinical improvement for >12 months but could actually make worse with sx (might be adhered to spinal cord, might be hard as a rock)- really just do sx to keep dog from getting worse -29% medically (steroids and rest) treated have sustained clinical improvement

Question 38

describe acute non-compressive nucleus pulposus extrusion (ANNPE) (6)

Answer 38

1. trauma ot vigorous exercise causes hydrated nucleus to herniate through tear in annulus and dissipate 2 clinical signs from contusion of spinal cord 3. any age (young more common) 4. any breed 5. acute (or peracute) onset -differential diagnosis with FCEM (see Kent lecture) 6. >80% improve with time

Question 39

describe IVDD in cats (5)

Answer 39

1. disc extrusion uncommon! 2. mean age is 9.8 years 3. reported prognosis with surgery 80% 4. ANNPE more common in cats 5. prognosis 90% for good recovery