The main findings in this prospective study are that dogs suffering SCI following acute intervertebral disc herniation treated surgically have similar neurological outcomes when they receive methylprednisolone versus NSAIDs, but that there was a significant difference in side effects between groups, with a higher percentage of dogs in the MPSS group having side effects than the NSAID group. Vomiting and anorexia were more prevalent in the MPSS group in our study, with statistically significant differences in the occurrence comparing with NSAID group. We considered vomiting and anorexia as consequences of gastrointestinal ulceration, because these signs were not present preoperatively. Renal function analyzes were performed only preoperatively to assure no comorbidity was present (an inclusion criteria request). We mentioned these aspects as limitations of the study. In humans, spinal cord injury is associated with increased risk of gastroduodenal ulceration, but the mechanism is not completely understood (Kewalramani 1979). Also, after high-dose MPSS treatment in patients with acute cervical spinal cord injury (Miekisiak et al. 2014), the authors observed that patients receiving high-dose MPSS had a significantly increased risk of major complications (gastrointestinal ulcer and bleeding). The treatment was not associated with an increase in mortality. In two studies, one hundred per cent of healthy dogs who received high dose MPSS had endoscopic evidence of gastric bleeding (Rohrer et al. 1999a, b). Concurrent treatment with gastrointestinal protectant drugs did not ameliorate this adverse effect. We didn’t use any gastrointestinal protectant drugs for the dogs in the study. In another study, 90% of dogs undergoing spinal surgery with adjunctive MPSS treatment had evidence of gastrointestinal bleeding assessed by faecal occult blood tests (Hanson et al. 1997). Olby et al. (2016) did not find any benefit of MPSS or polyethylene glycol in the therapy of acute, severe thoracolumbar IVDH used as adjunctive treatments administered to dogs in the first 24 hours of onset of paralysis. Boag et al. (2001) found that dachshunds with acute intervertebral disc disease treated with decompressive surgery and receiving MPSS had a significantly higher incidence of postoperative gastrointestinal complications rate, an increased use of gastrointestinal protectants, and also financial costs. We consider gastrointestinal bleeding and/or ulceration to be responsible for vomiting, anorexia and melena, with vomiting and anorexia significantly more prevalent comparing with NSAID group in our study.
Urinary bladder dysfunction is an important and common problem in perioperative cases of thoracolumbar IVDD (Kerwin et al. 2018). It was not possible to accurately determine preoperatively the urinary status of the population of dogs in our study due to the acute nature of the condition and the short amount of time spent in the hospital before the surgery. Ten dogs in MPSS group and 15 in NSAID group developed cystitis postoperative without statistically significant differences between groups. This is was somehow surprising for us and not very consistent with what has been reported in the literature. In a study conducted on 161 dogs with surgically confirmed IVDD (Levine et al. 2008), dexamethasone group dogs was 11.4 times as likely to have a urinary tract infection and 3.5 times as likely to have diarrhea, compared with other glucocorticoid and nontreatment group dogs. No differences in neurologic function at discharge or rre-evaluation were detected among groups. In another study (Mari et al. 2019) there was a strong significant association between not administering NSAIDs after diagnosis and a higher risk of faecal incontinence. In that study dogs that were administered NSAIDs (81 cases) were compared to dogs that did not receive NSAIDs (106 cases). In the latter group both dogs that did not receive any anti-inflammatory treatment (93 cases) and dogs that received corticosteroids (13 cases) were included. When dogs that received corticosteroids to dogs that did not were compared, no significant association with faecal incontinence was found (Mari et al. 2019). In any case, the low number of cases receiving corticosteroids and the lack of randomization, any direct comparison between the effect of these 2 classes of anti-inflammatory drugs on the occurrence of urinary infection or feacal incontinence was difficult to establish. Neurological grade at referral was also a predictor of urinary and faecal incontinence. This suggested that further prospective randomized studies are necessary to investigate NSAIDs treatment in dogs with acute nucleus pulposus extrusion.
Detrimental wound-healing effect and increased infection with the use of glucocorticosteroids both in humans and dogs were observed (Nishida et al. 2016; Levine et al. 2007).
There were no statistical significant differences regarding neurological recoveries of dogs in our groups. Recently, it has been shown that MPSS therapy in 50 dogs with surgically treated Hansen type-I thoracolumbar intervertebral disk herniation (TL-IVDH) significantly reduced the swelling of the spinal cord, although failed to provide any significant advance in recovery rate or length in time (Nishida et al. 2016). A study evaluating 233 dogs treated medically for presumptive thoracolumbar intervertebral disc herniation showed successful treatment (complete or substantial improvement without recurrence) in 55% of the dogs, with recurrence of paraspinal hyperesthesia, ataxia, or weakness in 31%; 14% of dogs were classified as therapeutic failures (decline in or lack of improvement after completion of medical therapy, or necessity for surgery or euthanasia within 1 month) (Levine et al. 2007). In that study, owners completed proxy quality of life scores for their dogs. Although duration of cage rest was not associated with outcome, administration of corticosteroids was negatively associated with both outcome and quality of life in a multivariate model that controlled for initial severity of spinal cord injury. Administration of NSAIDs was more likely to result in improved quality of life scores. The small population of dogs in our groups together with lack of any specific quality of life questionnaire for owner do not allow us to draw any major conclusion regarding quality of recovery.
Temporal effects of steroid administration limits how results of human trials can be extrapolating to veterinary patients. The human studies routinely showed either no benefit or worsened outcomes when patients received steroids more than 8h after spinal cord injury. Unfortunately for veterinarians, it is not always possible to identify the precise time of onset of disc-induced spinal cord injury in our patients, so we may find ourselves treating dogs with steroids well beyond any time frame where they might have had any potential benefit. Until we have prospective, blinded, large-scale studies in our patients with naturally occurring spinal cord injury, we cannot advocate using high-dose MPSS in our patients (Fingeroth and Thomas 2015).
Many veterinary clinicians continue to use corticosteroids such as prednisone or dexamethasone routinely at lower, anti-inflammatory doses for the management of canine IVDE (Moore et al. 2016). The question of whether treatment with non-steroidal anti-inflammatories (NSAIDs) or steroids is most appropriate represents a somewhat polarizing issue in veterinary medicine and is highly clinician-dependent (Moore et al. 2020).
Limitations of the study reported here included a small population in the two groups, lack of a control group and subjective assessment of anorexia and melena in treated dogs. Future studies with larger groups, ensuring that vomiting and anorexia are clearly due to anti-inflammatory drugs, with dogs having additional risk factors for gastrointestinal injury and bleeding, such as older age and presence of comorbidities, would better represent the clinical population of dogs receiving MPSS and NSAIDs. Any conclusions made in this study cannot be solely attributed to a single dose of MPSS preoperatively. Although such additional studies are warranted, our study results lead us to believe that the benefit of pre-operatively treatment with MPSS in chondrodystrophic does not support the use of this drug over NSAIDs prior to spinal surgery.
We have shown results supporting that MPSS use is associated with higher side effects than when using NSAIDs instead when using for IVDD in dogs. Side effects are significantly more evident with MPSS –including vomiting and anorexia during the first 3 days after surgery– than with NSAID, with an outcome recovery similar in both groups.