West Texas Colleagues,
It has been a blessing to be able to discuss a variety of cases with you over the last couple of months. I wanted to share a neurologic case that was recently imaged and operated with the help of the Lubbock Small Animal Emergency Clinic.
Presentation:
Signalment: 4-year-old male neutered Corgi
History: No prior medical conditions. 10-day history of paraplegia.
Physical findings: No significant joint abnormalities. Mentally appropriate. Forelimbs normal. Non-ambulatory paraplegic, extensor rigid in pelvic limbs. Pelvic limb reflexes normal. Conscious proprioception absent in pelvic limbs. Superficial pain intact on right (whines), absent left rear. Deep pain intact bilaterally (whines). Paraspinal muscle atrophy.
CBC/Chemistry: Minimally elevated ALT, attributed to recent steroid administration. No significant abnormalities.
Radiographic Findings:
Accompanying referral radiographs revealed in situ mineralization at T10-11 and T11-12, Mineralization was noted within the foramen and spinal canal at L1-2. A transitional T13 vertebra was also present.
Initial Treatment:
No improvement with carprofen and gabapentin therapy. After 4 days of initial treatment, carprofen was discontinued, and the patient was transitioned to anti-inflammatory prednisone and methocarbamol added. He continued to be able to urinate voluntarily but remained paraplegic 10 days after initial presentation. Spinal imaging with consideration of surgical intervention (based on imaging findings) was recommended as the best treatment option.
CT Findings:
T13 is transitional, with a left-sided vestigial rib. There are 7 lumbar vertebrae. On plain CT, there appears to be focal, right-lateralized mineralization at T12-13. There also appears to be left-lateralized material within the canal at L1-2. Given the finding of multiple lesions, a myelogram was performed (lumbar cisternal), and CT repeated. No significant compression was present at T12-13. There is severe spinal cord compression on the left at L1-2.
Diagnosis:
- L1-2 intervertebral disc extrusion with severe spinal cord compression (left)
- Incidental non-compressive disc extrusion T12-13 (right)
- Transitional T13 vertebra (vestigial left rib)
- Mildly elevated ALT
Surgical Findings:
A left-sided hemilaminectomy was performed at L1-L2, and a large amount of disc material was removed from the spinal canal. The spinal cord was mildly bruised.
Case Follow-Up:
At 3 weeks postoperative, the patient remains non-ambulatory but is exhibiting significant neurologic progress. He has maintained voluntary urination, is starting to push up on his rear limbs, and pelvic limb motor is present and improving.
Takeaways:
- Spinal cord injuries are one of the few true surgical emergencies.
- Efficient diagnosis and treatment provide an improved chance for recovery in most cases.
- If notable clinical improvement is not seen after initiating conservative management, spinal imaging should be considered.
- It is important to carefully evaluate anatomy for surgical planning.
- Some dogs have multiple lesions! Chronic lesions are often non- to minimally compressive and do not explain severe deficits. It is imperative that appropriate imaging be utilized to determine if lesions are associated with significant compression to warrant surgical decompression.
FAQs About Backs:
Why is surgical timing critical in many neurologic cases?
A point to continue to emphasize to owners is that the longer the spinal cord experiences significant compression, the more likely a spinal cord injury will be permanent. Thus, longer duration of severe compression leads to longer postoperative recovery, reduced chance for recovery to ambulation, and risk for progression to absent deep pain sensation. General guidelines are that surgery is ideally performed within 24 hours of a patient becoming non-ambulatory. If strong motor is present, surgery can be delayed in some cases. However, it is imperative that the patient be regularly assessed for a change in neurologic status if referral is being considered. The best chance for recovery is with prompt treatment.
What is the success rate for patients managed conservatively?
As we have all experienced, some dogs will improve with rest and pain management. With conservative management, the most important component of care is severe activity restriction for 4-6 weeks. The thought behind this is to allow scar tissue to develop over an area of the disc that is inflamed and protruding, which takes significant time. When signs improve in a short period (days), dogs are at risk for acute herniation if they are allowed excessive activity. Approximately 50% of dogs will improve with conservative management. In my experience, this is more likely in dogs with mild neurologic signs. Importantly, approximately 30% of dogs that improve with medical therapy will develop recurrent signs. In dogs who respond favorably to conservative management, significant improvement is expected within the first week of therapy.
What is the success rate for patients managed with surgery?
The most important prognostic indicator for recovery to ambulation after surgical treatment is the presence of deep pain sensation. It is important that the withdrawal reflex is not mistaken for conscious pain perception, as this is a simple spinal reflex. Intact pain sensation needs to be proven by a conscious act like vocalization, head turning, or attempting to bite. Approximately 90% of patients who have acute disc ruptures and intact pain sensation will recover following surgery. When deep pain is lost, approximately 50% will recover if surgery is performed within 24 hours of loss of sensation. Although there are conflicting outcomes reported in the literature, those patients with absent deep pain who are treated beyond 24 hours have a very low chance for recovery. Additionally, it is important to remember that any dog that loses deep pain can develop fatal ascending myelomalacia, generally within 3-5 days.
How long does it take for patients to recover following surgery?
It can take weeks to months for patients to regain the ability to walk, depending on their clinical history and the severity of injury. When a patient develops acute signs (with intact pain sensation) secondary to IVDD and undergoes timely surgery, the average time to walking is 2-4 weeks postoperative. For patients who have experienced signs for many days to weeks, recovery is significantly longer and less predictable. Rehabilitation therapy can be used to facilitate recovery following spinal surgery. Another factor that is important during recovery is bladder expression until voluntary urination is established. This can be a challenge in some patients who are painful or uncooperative and can become a quality-of-life issue.
What is the indication for CT vs. MRI?
We are all familiar with dog breeds that are predisposed to IVDD, as well as the typical presentation. CT is helpful in diagnosing canine disc disease because the disc material is frequently mineralized. CT is also more rapid to perform, and generally more accessible. In cases of non-mineralized lesions, CT with myelography can be performed. Although myelography is often well tolerated, it can be associated with focal seizures, status epilepticus (especially when intracranial or inflammatory CNS disease is present, or the patient has a known seizure disorder), and worsening of neurologic signs. Seizures are also more common in large breeds, due to the volume of contrast agent required for imaging. In general, CT is best suited to small to medium, at-risk breeds with an acute onset of signs that can be localized to T3-L3 or the cervical spine. MRI is frequently considered for medium to large breeds, those with intracranial or multifocal signs, atypical onset of signs, chronic neurologic disease, and/or those who are unlikely to tolerate a myelogram.
Are there options for prevention of IVDD in dogs?
Laser disc ablation (LDA) is a minimally invasive procedure that can be used to treat the 7-8 highest-risk disc spaces in the thoracolumbar spine, reducing the risk of herniation. It is highly effective in preventing herniation at the treated sites (approximately 97%). Unfortunately, the entire spine cannot be treated due to the risk for injury to major nerve roots or thoracic structures. In patients who have a history of spinal issues, neurologic signs must be stable, and no medications are needed to control signs for a minimum of 6 weeks prior to treatment. This procedure is performed in Dallas and Oklahoma.