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What is degenerative myelopathy?

Degeneration of axons + myelin in the thoracolumbar spinal cord

Genetic--mostly in German Shepherds


What are the signs of degenerative myelopathy?

  • Over months (6-36) progressive paresis and ataxia
    • Palpation very important--must differentiate from hip dysplasia (in which steroids would improve condition)
  • > 8 yrs--German Shepherds and others--Chesapeake, Boxer, Corgi, Ridgeback, Standard poodle, Kerry blue
  • Pelvic limb
    • Knuckling, dragging, crossing (walk in tight circle--back legs swing out/cross), dysmetria, ataxia 
      • Often see scuff marks on dorsal aspects of digits
    • Often asymmetrical 
    • Continence + pain spared (still feel pain on hind legs)
    • Later get LMN signs
  • Progressive = eventually will affect front limbs


In a dog with degenerative myelopathy, what will you find during a clinical exam?

  • Conscious proprioeptive deficits (possibly)
    • Scruffy motions, will leave paw upside-down when you displace it, etc.
  • UMN signs:
    • Hyperreflexia
    • Normal pain sensation
  • No spinal hypesthesia (not painful when palpaiting down spine)


How do you diagnose degenerative myelopathy? How do you treat it?

  • Diagnosis
    • Histopath--not practical
    • Exclusion--no changes on x-rays; normal CSF
    • Myelin basic protein elevated?
      • Could be, but it increases when anything goes wrong with the spinal cord--isn't specific to DM
    • DNA test--superoxide dismutase 1 protein
      • Not all animals with the gene are affected, but 100% of the animals affected have the gene
  • Treatment
    • NONE--cortico's, NSAIDs, B + E vit do nothing
    • Good nursing/physiotherapy - months - euthanasia
    • Aminocaproic acid/aminocysteine
      • Supposedly worked in trial, but no paper ever published (= sketchy)


Lumbosacral malarticulation-malformation (instability)

Particularly in working dogs--transfer of forces (back legs to front)


Type II disc degeneration--general

See pain + LMN signs

Annulus fibrosis, interarcuate ligament

Doesn't act as a shock absorber anymore



What instability is seen with type II disc degeneration?

  • Stenosis
  • Sacral facet osteophytes
    • L7 and S1 can move from side to side (normally fixed in place)--> continues to damage cauda equina by trapping it between the two vertebrae
  • Yellow ligament can thicken--> pressure on cauda equina from above


What is the signalment and history of type II disc degeneration?

  • Signalment
    • Older, large breed, working dogs
  • History
    • Hunched
      • Takes away pain or could be from losing function of sciatic nerve
    • Rising/stairs, flacid tail,
    • Incontinent (far down the line)


What is seen during the physical exam of a dog with type II disc degeneration?

  • Pain
    • Palpation L7S1
    • Lordosis test (won't differentiate from hip problem)
    • Tail jack test
      • Better test--localizes pain to L7S1 joint
  • Paresis
    • Sunken hock
    • Sciatic and flexor
    • Pudendal (hyporeflexia)
    • Hyperreflexia in patella
      • Sciatic n. not functional to act against the knee jerk reflex
    • Tail
  • Only hip flexes--controlled by femoral n.


What is the diagnosis?

Type II disc degeneration (lumbosacral instability)


What is this? In which breed is it most common? What does it predispose the dog to developing?

Transitional vertebrae--most common in GSD

The vertebra is joining the pelvis on one side and making a transverse process on the other

Dogs with this instability are predisposed to developing lumbosacral instability


What is the treatment for lumbosacral instability (type II disc degeneration)?

  • Cage rest + NSAIDs don't do much--working dogs don't rest well
  • Dorsal laminectomy +/- stabilization (80%)
    • Incontinence +/- response
    • Drill away 'roof' of bone so cauda equina is no longer compressed
  • Various materials used--problematic 


Thoracolumbar intervertebral disc disease--general

  • 70% of neuro cases
  • Discs (not C1/C2)--shock absorbers, movement
  • 2 types of degeneration
    • Aging
      • Fibrocartilage vs. hyaline cartilage


What are the 2 types of disc disease/prolapse?

  • Hansen type I
    • Chondrodystrophic breeds >3 yr
    • Explosive extrusion (like a bullet--painful) 
    • Acute progression, hyaline degeneration
    • Can feel within spinal cord--gritty, very painful
    • Dorsal longitudinal ligaments
    • Spinal cord compression
      • Cuts off blood supply--> all kinds of problems, including neuro dysfunction
  • Hansen type II
    • Large breed dogs >5 yr
    • Slow protrusion
    • Dorsal ligaments
    • Fibrocartilage degeneration (heals, then ruptures more, heals some, ruptures more, etc.)
    • Worse prognosis


What are the signalments for thoracolumbar intervertebral disc disease?

  • Adults 3-5 yr
    • Dachs > Poodles > Peeks > Beagles
  • Cats--50-100%
    • Calcifications common, problems rare
    • Occasional pain/paresis


History and clinical signs for thoracolumbar intervertebral disc disease?

  • Seldom T2-T10--inercapital lig.
  • >75% T11-L2
  • 15% cervical
  • UMN signs, UMN bladder
  • Paralysis (disc blown out spinal cord-->no info going through) + anesthesia - hyperesthesia (disc torn dorsal lig.-->stretching of nerve roots-->painful)
  • As spinal cord is compromised there's a sequential dec. in function:
    • Conscious proprioception
    • Voluntary motor + continence
    • Superficial pain
    • Deep pain


What does the treatment for lumbosacral instability depend on?

  • Treatment depends on grade of severity:
    • Grade 1 = spinal inc. esthesia w/o neuro def
    • Grade 2 = paresis but ambulatory 
    • Grade 3 = paresis but non-ambulatory (dragging but attempts to move legs)
    • Grade 4 = paralysis + deep pain intact
    • Grade 5 = paralysis w/ loss of deep pain 


What is the treatment for grades 1, 2, and 3 thoracolumbar intervertebral disc disease?

  • Strict cage rest--2 weeks; 80-100% ok
    • If still deteriorating, chance of relapse (33%)
  • Pain--NSAIDs seldom effective
    • Pred/doxy very effective but worse prognosis (slows healing) + side effects:
      • PU/PD, GI bleed, UTI, muscle, behavior, Addisons's
      • Can use low dose infrequently
    • Tramadol
    • Diazepam/methocarbanol/gabapentin?
      • Muscle relaxants
    • Polyethylene glycol (PEG)
  •  Physio--no improvement in 2 weeks-->surgery 


What is the treatment/prognosis for grade 4 thoracolumbar intervertebral disc disease?

  • 50-70% improve with cage rest
    • Relapses common, recovery slow (wks to mo.)
  • Empty bladders q. 4-6  hr
    • UTIs 20%
      • Duration biggest risk (best way to prevent is new sterile catheter 3x day)
    • Manual expression--must teach owners (can send musc. relaxers to dec. tone)
  • Watch for deterioration
  • Surgery best
  • Dorsolateral hemilaminectomy + fenestration


What is the prognosis/treatment for grade 5 thoracolumbar intervertebral disc disease?

  • Severe, often irreversible sc injury
    • <10% recover w/ cage rest
    • ~50% recover w/ surgery if within 48hrs
      • <10% recover if over 48hrs
  • Dorsal hemilaminectomy and durotomy
    • Improvement may take days or months
    • No deep pain by 2 weeks-->not likely to improve, consider euthanasia
  • Intensive nursing is vital + physiotherapy


What is the prevention for thoracolumbar intervertebral disc disease?

  • No risk factors
  • Percutaneous laser disc ablation
    • Percutaneously placed needles T10 to L4
    • 4% recurrence vs. 10-20% (mostly don't need surgery)



  • Bacterial infection of end plate and disc
  • S. intermedius, B. canis + Strep
  • Hematogenesis--skin, urinary, heart, testes


What are the signs associated with diskospondylitis?

  • Large, middle-aged male dogs
  • Hansen type II
  • Hyperesthesia (severe back pain), fever, depression, weight loss
  • Untreated:
    • Proliferation
    • Spinal cord compression + neuro signs 
      • Creates space between vertebrae--> body tries to seal off infection with bone--> protrudes--> pressure put on sc
  • Any dog that comes in with fever + back pain--> THINK DISKOSPONDYLITIS--don't want to wait until neuro signs appear


How do you diagnose diskospondylitis?

  • Spinal cord signs + systemic signs
  • Radiographs--lysis, sclerosis, spondylosis (C6/7, T4-6, L7S1)
    • Will see 'hot spots' in bone--where inflammation is occurring (more RBCs)
  • CSF normal--infection is in bone, not spinal cord
  • Serology--Brucella **zoonosis** 


What is the treatment for diskospondylitis?

  • Minimal dysfunction--just antibiotics based on culture results
    • Usually comes from UTI--can take urine sample and culture
    • *Must know exactly which bac. you're dealing with--difficult for antibiotics to penetrate bone so MUST use the correct one
    • BacterioCIDALs (NOT bacteriostatics--need to kill the bac.)
  • Parenteral for 5 days; oral 54 weeks 
  • Should show clinical improvement in 5-7 days 
  • Treat until radiographs resolve 
  • Neurological signs--hemilaminectomy and curettage


What are the generaly types of vertebral and spinal neoplasias? Which are more common in dogs and cats?

  • Intramedullary (tumor within spinal cord)--primary and mets
  • Intradural-extramedullary 
  • Extradural
  • Dog
    • 50% ost/fibro/chon
    • 30% - meningiomas
    • 20% - hemangiomas
  • Cat
    • lympho - FeLV 80-90%
    • Meningiomas
    • Any cat with progressive spinal cord dysfunction


What is this an example of?

Intramedullary spinal neoplasia

Vertebral columns get wider and wider because the tumor is creating pressure--> causes them to expand


What is the treatment for vertebral/spinal neoplasia?

  • Meningiomas/MPNSTs--resect
    • 6m (dog)
      • Can get slightly better result if irradiate site after surgery
    • 6-12m (cat)
  • Vertebral tumors--remove/irradiate for time
    • Not much you can do
  • Lymphoma--5 (FeLV) - 7 months


What causes most vertebral fractures/luxations? What are the signs? Diagnosis?

  • Trauma--sacroiliac/thoracolumbar
    • Lumbosacral most common
  • Tail tugs in cats
  • Signs
    • History, wounds, fracture, nails, shock
    • Can see LMN signs for up to 24 hrs
    • Spinal hyperesthesia/anesthesia paresis/paralysis, crepitus, alignment, Shiff-Sherrington
  • Diagnosis
    • Radiographs/myelograms


What is the treatment for vertebral fractures/luxations?

  • Shock/life threats treated first--colloids best
    • Methelpred succinate--shock, inflammation (IV, need high quantities)
  • Pain--opiates needed usually
    • Spinal edema--20% mannitol (shock, hypovol)
      • Vomiting, hemolysis
      • Give very slowly, only use once to stabilize cariovascular system
  • PEG
  • Surgery decompress/stabilization (dep. on rads)
    • < 4hr + deep pain
    • Large dogs (20kg)--ext. coaptation
    • Small dogs/cats - splint and rest
    • Surgery; hemilamin, plates, pins, etc.