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Staging, Diagnosis and Management of Cervical and
Thoracolumbar Intervertebral Disc Disease

Prepared on behalf of Veterinary Surgery Center by
C.H. “Skip” Tangner D.V.M., M.S., V.S. Diplomate ACVS
January 10, 2010

Intervertebral Disc/Disk Disease (IVDD)

Most common neurological syndrome in dogs(2.3% of hospitalizations of all dogs JAVMA-232,2008
Pathophysiology.

Chondroid metaplasia in chondrodystrophoid breeds leads to early (8 months- 2 years of age) degeneration of 75-100% of all intervertebral discs.
Degeneration of affected discs is noted by increased collagen and less proteoglycan that lead to decreased disc pliability, mineralization of the nucleus pulposus, and disruption of the lamellae of the annulus fibrosus.
Degenerated discs are less effective biomechanically and are predisposed to herniation or extrusion of nuclear and annular material into the spinal canal causing spinal cord trauma/displacement/pressure, pain and neurological dysfunction.

Hansen Type I disc protrusion

Nuclear material passes through the outer fibrous disc to lie freely in the vertebral canal.
Most common in chondrodystrophoid breeds (Dachshunds, Lhasas, Pekingese, etc.).
Happens in non-chondrodystrophoid breeds, in both the cervical and T-L areas.( JAAHA 40:316-320 2004
Most frequent between 2 and 7 years of age (peak incidence at 4-5 years).

Hansen Type II disc protrusion
1. Disc material (annular bands) protrude into the spinal canal.
2. Most common in non-chondrodystrophoid breeds (Bassett and German Shepard) between 8-10 years old L-1/L-2 most commonly affected site).

Neurological Examination (see neuro exam sheet)
1. History
2. Evaluate mental status, posture, and gait.
3. Cranial nerves.
4. Postural Reactions.
5. Spinal Reflexes.
6. Sensory abilities.
7. Urinary function.
Staging of disease (JAVMA 231, No 6, 2007)
1. Stage or Grade 1
  Back pain only. No Neurological dysfunction.
2. Stage or Grade 2
  Mild ataxia with enough conscience motor function to bear weight. Deep pain present.
3. Stage 3
  Nonambulatory, minimal ability to stand. Deep pain present.
4. Stage 4
  No motor function (paralysis), but dog can feel painful stimuli. Dog may or may not have urinary dysfunction.
5. Stage 5
  Dog is completely paralyzed and unaware of deep pain stimuli applied to the toes and tail. Urinary dysfunction present.
Common Differential Diagnosis
1. Cervical Disc Disease
  1. Meningitis/myelitis (not unusual even in Dachshunds)
  2. Static and dynamic stenosis from cervical vertebral instability (Wobbler’s Syndrome)
  3. Interdiscal osteomyelitis (diskospondylitis)
  4. Neoplasia (plasma cell myeloma, lymphoma, osteosarcoma, metastatic disease.)
  5. Trauma(C-1 to C-2 instability).
  6. Vertebral malformation/stenosis (Basset, King Charles)
  7. Polymyositis
  8. Polyarthritis (immune mediated most common)
  9. Fibrocartilaginous emboli/vascular disease
  10. Tick borne diseases
2. Thoracolumbar Disc Disease
  1. See 1-10 above.
  2. Prostate disease
  3. Abdominal pain (multiple causes)
  4. Lumbosacral disease
  5. Bilateral hip or cruciate disease
Diagnosis
1. History, Breed (Dachshunds makeup 56% of all cases operated for T-L disc disease.), Clinical Signs, Neurological examination.
2. Survey Radiology (These should be used for screening purposes only and not for determining the side of the disk herniation-see 2 below)
  1. Lateral and Ventrodorsal views of the spine in anesthetized patient.
    1. Signs of disc disease.
      - Narrowing or wedging of the IVD space or intervertebral foramen.
      - Visible intraspinal disc material.
      - Collapse of the articular facets.
    2. Interdiscal osteomyelitis
    3. Vertebral neoplasia
    4. Spinal fracture/luxation.
  2. Accurate determination of spinal cord compression and pinpoint lesion determination is unreliable with survey radiography alone. Boarded Radiologists miss the lesion on survey images in up to 20% of cases.
    In one study of cervical disk disease (JAAHA Vol. 37 No. 6, 563-572, 2001) the accuracy of correct identification on survey images was only 35%. An area of suspicion was detected in 61% of 64 cases of confirmed cervical disk herniations. Also 19% of the 64 dogs had more than one site of herniation. The major site of disc herniation was incorrectly identified in up to 31% of survey radiographs.
3. Myelography (greatly assisted by fluoroscopy)
  1. Iohexol (0.3mg/kg) or Iopamidol are contrast agents of choice.
  2. Injections are usually made in the cisterna magna or the L4-L5 or L5-L6 space.
  3. Exact site of disc herniation is correctly determined up to 97% of the time. Paradoxical contrast obstruction must be accounted for on VD images (JAVMA Vol 230, No 12, 2007) Paradoxical contrast obstruction is noted when the disc is herniated on the side of the spinal canal that has the shortest interrupted length of contrast flow. This is not a problem with CT or MRI studies.
  4. 21.4% of 182 cases had one or more seizures following Iohexol myelogram. Larger dogs (increased contrast volume) and cisternal punctures increased the risk of post-myelogram seizure. Seizures following a lumbar injection are rare.
  5. Poor contrast flow over five vertebral lengths is associated with a very poor prognosis and a high incidence of myelomalacia.
  6. CT and MRI are better for localizing the exact site and side of disc herniation. The most UNRELIABLE sign of lesion lateralization is clinical presentation. Clinically one side may be more severely affected neurologically but the affected side is not routinely the side of disc herniation. 25-50% of the time the disc material is on the side opposite the leg most affected clinically.
  7. MRI is the best modality to evaluate the spinal cord in severely affected cases of acute noncompressive nucleus pulposus extrusion and spinal cord trauma (JAVMA 234, No. 4, Pg 495, 2009). The T2 weighted image appears to be the best for evaluating trauma and disc extrusions (JAVMA 232, No5, pg 702, 2008). An MRI lesion length-to-vertebral length ratio > 2.0 or a percentage cross sectional area of the lesion >67% is associated with a poor prognosis in ischemic myelopathy (JAVMA 233; No 1 pg. 129, 2008).
Treatment
1. Nonsurgical/medical(walking dogs only: stage 1 & 2 cases)
  1. Confinement. 2-4 weeks of “pet taxi” confinement is typically recommended but one study did not see a correlation between length of confinement and recovery (Vet Surgery 36: 482-491, 2007)
    1. Harness or leash when outdoors to eliminate.
    2. Avoid slippery/slick surfaces.
    3. No running, jumping climbing or playing with other pets.
  2. Medications (Avoid dexamethasone and Methylprednisolone).
    1. Steroid use and Disc Disease.
      - No benefit from Pred, Dex or MPSS in cervical disease or FCE (Vet Surgery 36:492-499, 2007).
      - Associated with failure in T-L disc disease. 45 of 49 dogs with disc disease given steroids had one or more adverse steroid reactions. With Dexamethasone there was 3.4 times more complications (11.4 x more UTI and 3.5 x more diarrhea) compared to giving Pred or no steroid use at all.
      - Methylprednisolone was promising experimentally but no significant positive effect has been noted in human or canine clinical studies. MPSS given more than 8 hours after injury results in a worse outcome and decreased quality of life than not giving steroids at all. 90% of dogs have some degree of GI hemorrhage after MPSS treatment (J Vet Internal Med 13:399-407, 1999).
      - In one study of 308 dogs (Vet Comp Orthop Traumatol, 19:29-34, 2006) there was no difference in the ability to regain ambulation or the time to regain ambulation between dogs treated with any form of steroid and those patients receiving no steroids at all.
      - Steroids, especially in high dosages, can lead to excitotoxic neuronal death, worsening of oxidative injury through phospholipase A2 inhibition and lactate accumulation in the spinal cord.
  3. Pain Control
    1. NSAIDS with or without Tramadol (can give Tylenol/codeine [1/2 – 1 mg per lb codeine every 8 hours] with NSAID if necessary)
    2. Acepromazine may accentuate the effect of pain meds and is often given in the evening to help painful patients sleep.
    3. Approximately 80% of ambulatory disc cases will get better. Slowly return successful cases to full activity over 10-14 days after clinical signs are resolved. Unfortunately the recurrence rate with nonsurgical/medical therapy is as high as 50%.
      d. Surgery is the best choice for a good outcome if walking dogs get worse or are still painful after 3 weeks (CompCont Ed 30: No9, 2008)
  4. Acupuncture (improved nerve regeneration is the suspected mechanism of action) (JAVMA Vol 231, No6, 2007)
2. 1. 50 dogs with signs of unconfirmed T-L Disc Disease
    1. 2 groups
      - Group 1: 26 dogs with clinical signs for 5-60 days treated with acupuncture, 1mg/kg Prednisone on a reducing dosage schedule and Tramadol and Ranitidine if considered necessary.
      - Group 2: 24 dogs with clinical signs for 3-21 days treated only with the medications given to Group 1
    2. Results:
      - Group 1: (88.5% [23/26] recovered). Dogs with Grade 1 & 2 dysfunction had significantly longer clinical signs (5 – 60 days) than similarly affected dogs in Group 2 (3 – 21 days).
      - Group 2: (58.3% [14/24] recovered)
    3. Conclusion:
      Acupuncture appears beneficial for walking dogs with Grade 1 & 2 suspected T-L Disc Disease. Success rate with acupuncture is less than that expected for surgery; more and better studies need to be performed to confirm the benefit of acupuncture over medical management alone. The duration of clinical signs in this study would have eliminated all dogs with myelomalacia and many others with severe pain or progressive neurological dysfunction thereby influencing the success rate.
  2. Electroacupuncture seems to have minimal effect reducing pain in postoperative hemilaminectomy dogs. (JAVMA Vol 234 No.9, 2009)
Surgical Treatment
1. The purpose of surgery is to remove disc material from the spinal canal thereby eliminating pressure on the spinal cord. Laser disc ablation, fenestration, medications and acupuncture do not eliminate mechanical pressure on the cord.
2. Surgery is the treatment of choice for nonambulatory dogs (Stage 3 – 5) (Compend Cont Ed Vol 30, No.9, 496, 2008).
  1. Surgery on dogs that can feel deep pain is reported to be successful (dog is pain free, can walk and control urination/defecation.) over 91% of the time.
  2. Surgery can be successful when performed at anytime after the onset of clinical signs on dogs that feel deep pain. However, I still treat these as emergencies and operate them as soon as possible to try to achieve the quickest and most complete recovery and to prevent worsening neurological dysnfunction.
  3. Dogs that do not feel deep pain should be operated immediately if possible or within 48 hours of the loss of the ability to feel. The prospect of a successful outcome after 48 hours of pain loss is minimal (7%).
  4. In one study only 58% of dogs that lost the ability to feel deep pain and were operated within 48 hours regained the ability to walk. Intermittent urinary and/or fecal incontinence persisted in 41% and-32% of successful cases respectively. (JAVMA Vol 222, No.6 Pg 762,2003)
  5. I encourage operating cases that have lost pain within 48 hours of onset if the owners are willing since many dogs will do better than expected. A surprising percentage of Stage/Grade 5 dogs will recover like Stage/Grade 3-4 ones do.
Recovery
1. Nonsurgical Therapy (Best if used only on walking dogs)
  1. In one study of T-L Disease (223 dogs) 83% were walking at initial visit. Successful outcome was defined as significant improvement in clinical signs with no recurrence.
    53% were successful, 30.9% had significant recurrence and 14.4% did not improve at all or got worse. Duration of cage rest had no effect on success or quality of life and steroid use (especially Dexamethasone) was negatively associated with success and quality of life. NSAIDS had higher quality of life scores. (Vetsurgery 36:482-491, 2007)
  2. In other studies with a less strict definition of success 75-85% of Grade 1 and Grade 2 cases recovered with nonsurgical therapy alone. The average time to recovery was 4-6 weeks as compared to 12.9 days with surgery. Approximately 65-70% of Grade 3 and Grade 4 cases recovered with nonsurgical therapy. Many dogs in this group treated without surgery will not fully recover. Most will have prolonged recovery time and about 20% will deteriorate neurologically. Recurrence rates were high. Only about 7% of cases with Grade 5 disease walked after nonsurgical therapy and most had persistent neurological deficits. Grade 5 cases that improved would probably have been excellent surgical candidates with excellent results.
  3. Cervical Disease
    1. 97% ambulatory at initial visit.
    2. 48.9% successful, 33% recurrence, 18.1% failure.
    3. No positive influence associated with cage rest or steroid use.
    4. NSAID use associated with success.
  4. Conclusion: Due to the high incidence of recurrence and worsening clinical signs owners should be given the choice of both nonsurgical and surgical options even in walking dogs. Nonsurgical therapy will be successful in about 50% of Stage 1 / 2 cases of cervical and T-L disc disease. Medical management should shift away from steroids, especially Dexamethazone and Methylprednisolone, to NSAIDS and pain meds (i.e. Tramadol or Tylenol.)
2. Surgical Therapy
  1. Surgery on dogs with deep pain: 96% of 107 dogs with deep pain had regained the ability to walk 3 months after surgery. The mean time to ambulation was 12.9 days. Dogs with voluntary motor immediately after surgery walked in 7.9 days versus 16.4 days in dogs without immediate post-op voluntary motor function.
  2. Surgery on dogs with loss of deep pain (Stage 5): 58-70% of dogs with Stage 5 disease (loss of deep pain sensation) will recover if surgery is performed within 48 hours of the loss of deep pain. In one study 14% of 87 cases were euthanized within 3 weeks of surgery. Seven of those had ascending myelomalacia. 41% regained deep pain and were able to walk. 11% walked without deep pain (spinal walkers) and 17% remained paraplegic without deep pain. Intermittent urinary (32%) and intermittent fecal (41%) incontinence were present in some dogs regaining deep pain and ambulation. Recovery time can range from 10 days to 7 months. 85% of owners of non-ambulatory dogs without deep pain felt their pet had a good quality of life using a cart to assist ambulation. In spite of incontinence, foot sores, etc. 74% believed their pet did not realize it was paralyzed. (JAVMA 222 No 6, 762, 2003)
  3. Dogs with lower motor neuron disease are 2 times more likely to regain strong ambulatory status and will walk sooner than dogs with upper motor neuron disease (JAAHA 35,323-331, 1999)
  4. Increasing age has a negative effect on quality of recovery.
  5. Postoperative physical therapy has little effect on post surgical outcome in dogs that feel pain postoperatively.
  6. Conclusion: Over 91% of paralyzed dogs that feel pain will get better with surgery. Dogs that can not feel pain should be operated ASAP and before 48 hours after the onset of clinical signs to expect reasonable results. Methylprednisolone and dexamethasone should be avoided. The intervertebral space at the site of herniation should be fenestrated (see Recurrent B).
Recurrence
1. In one study 44% of dogs with a recurrence of disc disease were euthanized.
2. Laser fenestration of multiple disc spaces or standard surgical fenestration reduced the recurrence of paralysis to 3.4% of 277 cases. The recurrence rate of any sign of disc disease is about 25% following fenestration. In one study (VetSurgery 37:395-405, 2008) a 6 week post-hemilaminectomy MRI documented reherniation of disc material at the operated disc site in 6 of 10 dogs not fenestrated at surgery. None of the dogs fenestrated at the original surgery had additional disc in the spinal canal. Fenestration will NOT remove intraspinal disc material and it does extend postoperative morbidity.
3. Hemilaminectomy without fenestration : 4.4- 7% re-operations rate (30 of 467 dogs and 17 of 250 dogs). 18% of the 250 cases had recurrence at the original operations site. 35% were adjacent to the original site and 47% were 2 or more spaces away from the original herniation.
4. hemilaminectomy with fenestration: 4.4 % re-operation rate (265 cases)
5. In one study (JAVMA Vol 225, No. 8 1231,2004) 96% of recurrences (44 of 229 dogs (19.2%) developed within 3 years after surgery. Recurrence happened in 25% of Dachshunds and 15% of dogs of other breeds. Each opacified disc seen radiographically increased recurrence rate by 1.4 times. Dogs with 5 or 6 opacified discs had a recurrence rate of 50%.
6. Dachshunds have up to a 9.5% re-operation rate. Other breeds have a re-operation rate of around 2.8%.
7. A large percentage of dogs with disc disease are euthanized because of recurrence. At minimum the intervertebral space of the herniated disc should be fenestrated. Disc ablation or fenestration should be considered for dogs with more than 4 opacified disc spaces.