Tinker’s owner, Hank, knew immediately that there was something seriously wrong with his two-year-old male neutered Chihuahua when he returned home from work on Wednesday. Rather than greeting Hank at the door as usual – jumping and barking — Tinker was crouched in his bed, shaking and whimpering. When Hank encouraged Tinker to move, he cried out and pulled himself out of the bed using just his front legs. His rear legs dragged uselessly behind. When Hank picked him up, Tinker screamed and tried to bite his beloved owner.
Tinker was rushed to see Dr. A. before closing. She found Tinks to be paraplegic with intact reflexes, good anal tone and exquisite pain at the thoracolumbar junction. She immediately considered intervertebral disk disease (IVDD) based on his presentation, neurological examination and history. She then gave him opiate and NSAID injections. She discussed with Hank her presumptive diagnosis of IVDD and other rule-outs (tumor, trauma, fibrocartilagenous emboli and infection/inflammation), along with next steps for diagnosis and treatment. Dr. A. explained that it was difficult for her to prognosticate without a definitive diagnosis, but counseled immediate action since this seemed to be a severe neurological dysfunction with a very acute onset.
Hank and Tinker were referred to the Anne Arundel Veterinary Emergency Center in Annapolis and arrived at 8pm. He was immediately seen, triaged and admitted. Emergency blood work was drawn, intravenous fluids were given and pain management was instituted. Dr. McDonnell and the VNoC team were called in and examined Tinker. We confirmed Dr. A’s findings, but found that Tinker had lost deep pain during the ensuing three hours to referral.
We discussed our diagnostic and treatment options with Hank. With Tinker’s signalment, history and examination findings, our primary differential was IVDD. Immediate diagnosis by emergency myelography was recommended.
Tinker’s blood work was normal. He was anesthetized and radiographs of the back were obtained. No obvious bony lesions were seen to explain his signs. A lumbar tap was performed, his CSF was found to be normal. A water-soluble iodinated contrast agent was injected in his subarachnoid space. The myelogram showed a classic extradural cord compression over the L1-2 disk space consistent with a diagnosis of Type I intervertebral disk extrusion.
Tinker was immediately prepped for emergency surgery. Dr. McDonnell did an emergency hemilaminectomy to remove the extruded disk and fenestrated disks spaces T12-13, T13-L1 and L1-2. Tinker was treated intra-operatively with a fentanyl, lidocaine and ketamine (FLK) CRI as well as a morphine splash over the surgical site. Post-operatively, Tinker was comfortable with the FLK CRI, gabapentin and a fentanyl transdermal patch.
Tinker’s outcome was gratifying to everyone; his pain sensation returned within 48 hours of surgery. Aggressive pain and anti-inflammatory management was continued. His UMN bladder was emptied with a combination of pharmacological intervention and manual expression. He received intensive rehabilitation exercise, stretching and massage.
Over the course of 14 days post-operatively, he regained strength in his rear legs and could rise and stand on his own. He could walk with assistance. After three weeks, he was independently ambulatory for up to 20 feet. Four weeks post-operatively, he surprised Hank by greeting him at the door, wagging his tail as if to say, “I’m ready to get back to our long walks.”
Figure 2: Lateral myelogram. There is a large L1-2 extradural compression likely due to intervertebral disk herniation.
Figure 3: Ventrodorsal projection myelogram. Thinning of the contrast columns over L1-2 with greater loss of contrast columns indicates a ventral and left-sided extradural compression consistent with an intervertebral disk herniation.
Presumptive Intervertebral Disk Disease (IVDD)
Presumptive disk disease in chondrodystrophic dogs is one of the most common neurological presentations in small animal veterinary medicine. There is a spectrum of presentation from simple back pain to the extreme case illustrated by Tinker, above. Being able to provide clients with accurate prognosis for these cases is very helpful. The most valuable tool at the outset is the neurological examination. Accurately assessing the neurological condition of the patient can mean the difference between emergency referral or medical treatment.
Our philosophy is that dogs with presumptive IVDD that are less than 6 years old and have strong motor should be treated medically. The dogs that cannot rise on their own, are non-ambulatory paraparetic or completely paralyzed would benefit with surgery for several reasons:
- Dogs treated surgically have a much more rapid recovery than dogs treated medically. We see functional recovery in surgically-treated dogs in 10-14 days, while those dogs treated medically usually recover in 4 weeks. Return to function decreases the co-morbidities of urinary tract infections, urine/fecal scald and muscle contraction.
- Recurrence of clinical signs due to relapse of the offending disk is less than 3% in dogs treated surgically, while relapse occurs in more than 30% in dogs treated medically.
Recurrence of signs secondary to an additional disk can and does occur in dogs treated both surgically and medically. Statistics are not available for dogs treated medically, but a recent article about dogs treated surgically reported that dogs treated surgically with fenestration recurred an average of 12.7%. There was a difference in recurrence between dogs fenestrated only at the extrusion site (17%) versus dogs fenestrated at multiple sites (7.5%).
Another remarkable point to consider in the table (above) and figure (at left) is the declining chances of functional recovery in animals delayed by just 1 or 2 days. For this reason, we recommend immediate referral when an animal that you suspect has disk disease presents with either non-ambulatory paraparesis or complete paraplegia (Grade 3 or greater). One recent study found that dogs that were Grade 4 had a 1.7 times better chance of becoming ambulatory than those with no deep pain perception.