von Frey anesthesiometry to assess sensory impairment after acute spinal cord injury caused by thoracolumbar intervertebral disc extrusion in dogs

Backbone breakthroughs: How rodent models are shaping intervertebral disc disease treatment

Intervertebral disc degeneration (IVDD) is a widespread, disabling condition that significantly contributes to the global burden of musculoskeletal disorders. To better understand its underlying mechanisms and explore potential therapeutic strategies, animal models serve as valuable tools for simulating the complicated pathophysiology of IVDD. Rodent models are extensively used due to their genetic similarities to humans, cost-effectiveness, and rapid attainment of maturity. These models enable the study of specific molecular pathways involved in IVDD, such as inflammation, matrix degradation, tissue repair, and disc microenvironment homeostasis. This review provides a comprehensive overview of the current status of rodent models used in IVDD research, highlighting their advantages, limitations, and contributions to our understanding of the disease. Specifically, we discussed various rodent models, including traumatic (such as needle puncture in the lumbar and coccygeal region, nucleotomy, and annulus fibrosus defect), non-traumatic (including compression models, lumbar spine instability, and bipedalism), chemically induced models (chymopapain, chondroitinase ABC), and genetically modified models. These models offer insights into the severity of IVDD under different conditions, such as trauma, aging, and genetics. In conclusion, rodent models remain indispensable tools for advancing our understanding of IVDD mechanisms and therapeutic interventions. Carefully selecting animal species and models can provide valuable insights that guide future clinical research and treatment approaches. Our review aims to leverage these models to identify therapeutic targets and strategies that may ultimately reduce the impact of IVDD on human health. PERSPECTIVE: This review describes the role of rodent models in IVDD, highlighting their utility in unraveling disease mechanisms and evaluating therapeutics. By replicating the complex molecular pathways and conditions of disc disease, like trauma, aging, and genetics, these models aid in identifying future advancements in managing lower back pain.

The Effectiveness of Liposome-Encapsulated Bupivacaine Compared to Standard Bupivacaine for Anesthesia of the Maxilla in Dogs

Medical and surgical procedures involving the canine maxilla can be painful both during and for several hours post-procedure. The length of this pain may exceed the predicted duration of standard bupivacaine or lidocaine. The goal of this study was to determine the duration and efficacy of sensory blockade of the maxilla produced by liposome-encapsulated bupivacaine (LB), compared to standard bupivacaine (B) or saline (0.9% NaCl) (S), when administered as a modified maxillary nerve block in dogs. Eight maxillae were studied bilaterally from 4 healthy dogs of the same breed and similar age. This prospective, randomized, crossover, blinded study evaluated a modified maxillary nerve block using 1.3% LB at 0.1 mL/kg, 0.5% B, or S at an equivalent volume. An electronic von Frey aesthesiometer (VFA) was used to evaluate mechanical nociceptive thresholds at 4 locations on each hemimaxilla at baseline and at specific intervals up to 72-h post-treatment. Both B and LB treatments resulted in significantly higher VFA thresholds when compared to S. Dogs that received B had VFA thresholds significantly higher than S for 5 to 6 h. Dogs that received LB had thresholds significantly higher than S for 6 to 12 h depending on the site of measurement. No complications were observed. Maxillary nerve block with B provided up to 6 h, and LB 12 h, of sensory blockade depending on the site tested.

Quantitative sensory testing in canine musculoskeletal pain: Findings from a systematic review, meta-analysis feasibility assessment, and limitations

Quantitative sensory testing (QST) allows the study of pain mechanisms, patient phenotyping, and response to therapy. The goals of this study were to conduct a systematic review of the use of QST in dogs with musculoskeletal disease including osteoarthritis (OA), and to assess, by means of a meta-analysis, the ability of QST to differentiate affected dogs from healthy controls. The study protocol was registered; three bibliographic databases were screened. Studies involving QST in healthy dogs and those with musculoskeletal disease were included. Data were extracted using a standardized form. Assessment of quality and risk of bias were performed using the CAMARADES critical assessment tool. Twenty-nine articles met the inclusion criteria [systematic review (n = 11); meta-analysis (n = 28)]. In the systematic review, ten studies performed static QST: mechanical [punctate tactile (n = 6); mechanical pressure (n = 5)]; thermal [cold (n = 3); hot (n = 4)]; electrical (n = 1); and one study performed dynamic QST [conditioned pain modulation (n = 1)]. Most studies were of good scientific quality and showed low to moderate risk of bias. A meta-analysis was not possible due to numerous and severe issues of heterogeneity of data among studies. Methods to reduce risk of bias and use of reporting guidelines are some of the most needed improvements in QST research in dogs. Standardization of QST methodology is urgently needed in future studies to allow for data synthesis and a clear understanding of the sensory phenotype of dogs with and without chronic pain including OA.

α-Gal Nanoparticles in CNS Trauma: II. Immunomodulation Following Spinal Cord Injury (SCI) Improves Functional Outcomes

BACKGROUND

Previous investigations have shown that local application of nanoparticles presenting the carbohydrate moiety galactose-α-1,3-galactose (α-gal epitopes) enhance wound healing by activating the complement system and recruiting pro-healing macrophages to the injury site. Our companion in vitro paper suggest α-gal epitopes can similarly recruit and polarize human microglia toward a pro-healing phenotype. In this continuation study, we investigate the in vivo implications of α-gal nanoparticle administration directly to the injured spinal cord.

METHODS

α-Gal knock-out (KO) mice subjected to spinal cord crush were injected either with saline (control) or with α-gal nanoparticles immediately following injury. Animals were assessed longitudinally with neurobehavioral and histological endpoints.

RESULTS

Mice injected with α-gal nanoparticles showed increased recruitment of anti-inflammatory macrophages to the injection site in conjunction with increased production of anti-inflammatory markers and a reduction in apoptosis. Further, the treated group showed increased axonal infiltration into the lesion, a reduction in reactive astrocyte populations and increased angiogenesis. These results translated into improved sensorimotor metrics versus the control group.

CONCLUSIONS

Application of α-gal nanoparticles after spinal cord injury (SCI) induces a pro-healing inflammatory response resulting in neuroprotection, improved axonal ingrowth into the lesion and enhanced sensorimotor recovery. The data shows α-gal nanoparticles may be a promising avenue for further study in CNS trauma.

Effect of gonadectomy on pain assessment in dogs undergoing orthopaedic stifle surgery

OBJECTIVE

To compare pain perception between gonadectomized and intact dogs.

STUDY DESIGN

Blinded, prospective, cohort study.

ANIMALS

A group of 74 client-owned dogs.

METHODS

Dogs were divided into four groups: group 1-female/neutered (F/N), group 2-female/intact (F/I), group 3-male/neutered (M/N) and group 4-male/intact (M/I). Premedication consisted of intramuscularly administered acepromazine (0.05 mg kg-1) and morphine (0.2 mg kg-1), and subcutaneously administered carprofen (4 mg kg-1). Anaesthesia was induced with propofol (1 mg kg-1 intravenously and supplementary doses to effect) and maintained with isoflurane in 100% oxygen. Intraoperative analgesia was achieved with fentanyl infusion (0.1 μg kg-1 minute-1). Pain assessments [using the University of Melbourne Pain Scale (UMPS) and an algometer at the incision site (IS), parallel to the incision site (NIS), and on the contralateral healthy limb] were performed preoperatively, and at 1, 2, 4, 6, 9 and 20 hours after extubation. The time-standardised area under the curve (AUCst) for measurements was calculated and compared by performing a one-way multivariate analysis of variance (manova). Statistical significance was set at p < 0.05.

RESULTS

Postoperatively, F/N exhibited higher pain than F/I, with estimated marginal means (95% confidence intervals) AUCstISGroup1 909 (672-1146) versus AUCstISGroup2 1385 (1094-1675) (p = 0.014), AUCstNISGroup1 1122 (823-1420) versus AUCstNISGroup2 1668 (1302-2033) (p = 0.024) and AUCstUMPSGroup1 5.30 (4.58-6.02) versus AUCstUMPSGroup2 4.1 (3.2-5.0) (p = 0.041). Similarly, M/N showed higher pain than M/I with AUCstISGroup3 686 (384-987) versus AUCstISGroup4 1107 (871-1345) (p = 0.031) and AUCstNISGroup3 856 (476-1235) versus AUCstNISGroup4 1407 (1109-1706) (p = 0.026), and AUCstUMPSGroup3 6.0 (5.1-6.9) versus AUCstUMPSGroup4 4.4 (3.7-5.2) (p = 0.008).

CONCLUSIONS AND CLINICAL RELEVANCE

Gonadectomy affects pain sensitivity in dogs undergoing stifle surgery. Neutering status should be taken into consideration when planning individualized anaesthetic/analgesic protocols.

Pilot Study on Feasibility of Sensory-Enhanced Rehabilitation in Canine Spinal Cord Injury

Physical rehabilitation is frequently recommended in dogs recovering from acute thoracolumbar intervertebral disc extrusion (TL-IVDE), but protocols vary widely. The objective of this study was to evaluate the feasibility of incorporating sensory-integrated neurorehabilitation strategies into a post-operative rehabilitation protocol in dogs with TL-IVDE. Non-ambulatory dogs with acute TL-IVDE managed surgically were prospectively recruited to this unblinded cross-over feasibility study. Eligible dogs were randomized to start with tactile-enhanced (artificial grass) or auditory-enhanced (floor piano) basic rehabilitation exercises performed twice daily for the first 4 weeks before switching to the opposite surface for the subsequent 4 weeks. Neurologic examination, open field gait scoring, girth measurements and an owner-completed feasibility questionnaire were performed at baseline and 2, 4, 6, and 8 weeks post-operatively. Twenty-four dogs were enrolled, 12 randomized to each order of exercises. Gait scores did not differ between the two groups at baseline, 4 or 8 week visits. All modified exercises could be performed and compliance was high. Adverse events potentially attributable to the study surface were mild, self-limiting and occurred in 2/24 dogs. The most common surface-related limitations were that the piano was slippery and that both surfaces were too short. The artificial grass was preferred by owners and dogs compared to the floor piano surface, but this was influenced by which surface was utilized first. Auditory and tactile modifications were feasible and safe to incorporate into a standardized rehabilitation protocol. This pilot study could prompt larger efficacy studies investigating the benefit of sensory-integrated rehabilitation in dogs with TL-IVDE.

Use of acupuncture as adjuvant analgesic technique in dogs undergoing thoracolumbar hemilaminectomy

The aim of this study was to investigate the analgesic efficacy of a preoperative acupuncture treatment in 24 client-owned dogs undergoing thoracolumbar hemilaminectomy. Dogs were randomly assigned to either group A (Acupuncture) or group C (Control). Before skin incision, group A was treated with acupuncture, performed under general anaesthesia for 30 min. Rescue intraoperative fentanyl was administered following a 20% increase in cardiovascular parameters compared to baseline values, measured before incision. An observer masked to the treatment assessed pain, pre- and postoperatively, with the Glasgow (GCPS), the Colorado (CPS) pain scales and a Visual Analogue Scale (VAS); additionally, the mechanical thresholds (MT) were measured with the Electronic von Frey Anaesthesiometer (EVF) at four points located near the herniated disc. The groups were compared with respect to intraoperative cardiovascular and respiratory variables, rescue fentanyl administered in total and at different surgical events (first incision [FI], drilling [DR], disc removal [RE] and skin suturing [ST]), and pre- and postoperative pain scores and MT. Group A received less fentanyl than group C (P = 0.014); this difference was significant at FI P = 0.035) and RE (P = 0.004). The improvement in postoperative CPS score (P = 0.013), VAS score (P = 0.003) and MT (P = 0.001) compared to preoperative values was greater for group A than for group C, whereas the treatment assignment had no effect on postoperative changes in GCPS compared to baseline. Pre-operative acupuncture may help improving perioperative analgesia in dogs with intervertebral disc herniation undergoing thoracolumbar hemilaminectomy.

Quantitative sensory testing of the equine face

BACKGROUND

Quantitative sensory testing methods are now standard in the evaluation of sensory function in man, while few normal equine values have been reported.

OBJECTIVES

The aim of this experimental study was (a) to define the tactile sensory, mechanical nociceptive and thermal nociceptive thresholds of the equine face; (b) to assess the effect of age, sex, stimulation site and shaving; (c) to evaluate the reliability of the methods and (d) to provide reference facial quantitative sensory testing values.

STUDY DESIGN

Method description.

METHODS

Thirty-four healthy Warmblood horses were used in the study. Six (tactile sensory threshold) and five (mechanical nociceptive and thermal nociceptive thresholds) areas of the left side of the face with clear anatomical landmarks were evaluated. Ten horses had two (mechanical nociceptive threshold) or three (tactile sensory and thermal nociceptive thresholds) of these areas shaved for another study. A linear Mixed model was used for data analysis.

RESULTS

All thresholds increased with age (tactile sensory threshold: by 0.90 g/y (CI = [0.12 g; 0.36 g]) P = .001; mechanical nociceptive threshold: by 0.25 N/y (CI = [0.13-0.36 N]) P = .000; thermal nociceptive threshold: by 0.2°C/y (CI = [0.055-0.361]) P = .008). Sex had no effect on thresholds (tactile sensory threshold: P = .1; mechanical nociceptive threshold: P = .09; thermal nociceptive threshold: P = .2). Stimulation site affected tactile sensory and mechanical nociceptive thresholds (P = .001 and P = .008), but not thermal nociceptive threshold (P = .9). Shaving had no significant effect on any of the thresholds (tactile sensory threshold: P = .06; mechanical nociceptive threshold: P = .08; thermal nociceptive threshold: P = .09).

MAIN LIMITATIONS

Only the left side was investigated and measurements were obtained on a single occasion.

CONCLUSIONS

Handheld quantitative sensory testing does not require shaving or clipping to provide reliable measurements. Stimulation over the nostril (tactile sensory threshold), temporomandibular joint (mechanical nociceptive threshold) and supraorbital foramen (thermal nociceptive threshold) resulted in the most consistent thresholds.

Mechanical quantitative sensory testing in cavalier King Charles spaniels with and without syringomyelia

BACKGROUND

Syringomyelia (SM) is a debilitating condition in the cavalier King Charles spaniel (CKCS) that results in neuropathic pain and diminished quality of life. Von Frey aesthesiometry (VFA) is a method of mechanical quantitative sensory testing that provides an objective sensory threshold (ST) value and can be used to quantify neuropathic pain (NP) and monitor response to therapy. The utility of VFA has been previously established in client-owned dogs with acute spinal cord injury but the technique has not been evaluated in dogs with SM. The goal of this study was to evaluate ST, as determined by VFA, in dogs with and without SM, to assess the utility of VFA in quantifying NP in SM-affected dogs. We hypothesized the SM-affected CKCS would have lower ST values, consistent with hyperesthesia, when compared to control CKCS. Additionally, we hypothesized that ST values in SM-affected dogs would be inversely correlated with syrinx size on MRI and with owner-derived clinical sign scores.

RESULTS

ST values for the thoracic and pelvic limbs differed significantly between the SM-affected and control CKCS (p = 0.027; p = 0.0396 respectively). Median ST value (range) for the thoracic limbs was 184.1 g (120.9-552) for control dogs, and 139.9 g (52.6-250.9) for SM-affected dogs. The median ST value (range) for the pelvic limbs was 164.9 g (100.8-260.3) in control dogs and 129.8 g (57.95-168.4) in SM-affected dogs. The ST values in SM-affected dogs did not correlate with syrinx height on MRI (r = 0.314; p = 0.137). Owner-reported clinical sign scores showed an inverse correlation with pelvic limb ST values, where dogs with lower ST values (hyperesthesia) were reported by their owners to display more frequent and severe clinical signs (r = - 0.657; p = 0.022).

CONCLUSION

ST values were lower in SM-affected CKCS compared to control dogs, suggesting the presence of neuropathic pain. Dogs with lower ST pelvic limb values were perceived by their owners to have more severe clinical signs classically associated with SM. Our results suggest that VFA might offer quantitative assessment of neuropathic pain in SM-affected dogs and could be useful for monitoring response to therapy in future clinical studies.

Companion animal models of neurological disease

Clinical translation of novel therapeutics that improve the survival and quality of life of patients with neurological disease remains a challenge, with many investigational drug and device candidates failing in advanced stage clinical trials. Naturally occurring inherited and acquired neurological diseases, such as epilepsy, inborn errors of metabolism, brain tumors, spinal cord injury, and stroke occur frequently in companion animals, and many of these share epidemiologic, pathophysiologic and clinical features with their human counterparts. As companion animals have a relatively abbreviated lifespan and genetic background, are immunocompetent, share their environment with human caregivers, and can be clinically managed using techniques and tools similar to those used in humans, they have tremendous potential for increasing the predictive value of preclinical drug and device studies. Here, we review comparative features of spontaneous neurological diseases in companion animals with an emphasis on neuroimaging methods and features, illustrate their historical use in translational studies, and discuss inherent limitations associated with each disease model. Integration of companion animals with naturally occurring disease into preclinical studies can complement and expand the knowledge gained from studies in other animal models, accelerate or improve the manner in which research is translated to the human clinic, and ultimately generate discoveries that will benefit the health of humans and animals.

Urological Sequelae to Acute Spinal Cord Injury in Pet Dogs: A Natural Disease Model of Neuropathic Bladder Dysfunction

The authors review urologic dysfunction, including urine retention, incontinence, and recurrent and resistant urinary tract infection, in dogs as a sequela to acute spinal cord injury. Urologic sequelae to acute spinal cord injury (SCI) pose significant complications in human and canine patients impacting quality of life and long-term cost of treatment. Dogs with intervertebral disc extrusion may serve as a natural disease model of acute SCI for investigating translational interventions, both prophylactic and therapeutic, for urologic dysfunction in human SCI patients.

Interobserver agreement of an electronic von Frey device for measuring mechanical sensory thresholds in normal dogs

Electronic von Frey Aesthesiometry (VFA) has been previously reported as a useful method of mechanical quantitative sensory testing (QST) for evaluating neuropathic pain in dogs. Intraobserver agreement has been shown to be good to excellent; however, interobserver agreement has not been evaluated and is vital to the use of this technique in multicenter veterinary clinical trials in neuropathic pain. The goal of this study was to evaluate the interobserver agreement of sensory thresholds obtained using electronic VFA in a group of normal small breed dogs. Twenty healthy dogs (<20 kg) were recruited from the general practice population at the Ohio State University Veterinary Medical Center. Three clinically experienced yet QST novice evaluators used an electronic von Frey device to measure mechanical sensory threshold (ST) after a standardised training session conducted by an expert evaluator. Each dog was assessed by all three evaluators on the same day with both evaluator and limb test order randomised and testing sessions separated by 5 min. Mean ST values were averaged for all four limbs to produce a single value per dog for comparison between evaluators. Agreement between evaluators was determined using the intra-class correlation coefficient (ICC; two-way model for consistency, single measures). ICC across all three evaluators was 0.48, indicating moderate agreement. Moderate interobserver agreement is not sufficient to support the use of this technique in multi-center clinical trials, and our results underscore the importance of using a single evaluator for this QST technique until better agreement can be demonstrated.

Quantitative sensory testing in dogs with painful disease: A window to pain mechanisms?

Evaluation of the response to externally applied physical stimuli, such as pressure, heat, or cold is termed quantitative sensory testing (QST). QST may be used to identify and quantify alterations (gain or loss) in function of the sensory systems which detect and mediate these phenomena in both man and animals, and potentially discriminate peripheral and central sensitisation. It has been postulated that evaluation of QST parameters may predict response to analgesics, ultimately increasing the individualisation of treatment for pain. However, while there do appear to be correlations between QST measures and responses to analgesics in man, there is currently insufficient evidence to recommend QST to direct clinical treatments. The use of psychophysical testing, such as QST, in non-verbal subjects presents additional challenges, and requires familiarity with species and individual responses. This narrative review describes the investigations into QST in clinical populations of dogs to date, and discusses the potential benefits and limitations of such testing.

Development of an International Canine Spinal Cord Injury observational registry: a collaborative data-sharing network to optimize translational studies of SCI

Study Design

Prospective cross sectional cohort study

Objectives

The canine spontaneous model of spinal cord injury (SCI) is as an important pre-clinical platform as it recapitulates key facets of human injury in a naturally occurring context. The establishment of an observational canine SCI registry constitutes a key step in performing epidemiologic studies and assessing the impact of therapeutic strategies to enhance translational research. Further, accumulating information on dogs with SCI may contribute to current “big data” approaches to enhance understanding of the disease using heterogeneous multi-institutional, multi-species data sets from both pre-clinical and human studies.

Setting

Multiple veterinary academic institutions across the United States and Europe.

Methods

Common data elements recommended for experimental and human SCI studies were reviewed and adapted for use in a web-based registry, to which all dogs presenting to member veterinary tertiary care facilities were prospectively entered over approximately one year.

Results

Analysis of data accumulated during the first year of the registry suggests that 16% of dogs with SCI present with severe, sensorimotor complete, injury and that 15% of cases are seen by a tertiary care facility within 8 hours of injury. Similar to the human SCI population, 34% were either overweight or obese.

Conclusions

Severity of injury and timing of presentation suggests that neuroprotective studies using the canine clinical model could be conducted efficiently using a multi-institutional approach. Additionally, pet dogs with SCI experience similar comorbidities to people with SCI, in particular obesity, and could serve as an important model to evaluate the effects of this condition.

The chondrodystrophic dog: A clinically relevant intermediate-sized animal model for the study of intervertebral disc-associated spinal pain

Low back pain (LBP) is the leading cause of disability worldwide, with an estimated 80% of the American population suffering from a painful back condition at some point during their lives. The most common cause of LBP is intervertebral disc (IVD) degeneration (IVDD), a condition that can be difficult to treat, either surgically or medically, with current available therapies. Thus, understanding the pathological mechanisms of IVDD and developing novel treatments are critical for improving outcome and quality of life in people living with LBP. While experimental animal models provide valuable mechanistic insight, each model has limitations that complicate translation to the clinical setting. This review focuses on the chondrodystrophic canine clinical model of IVDD as a promising model to assess IVD-associated spinal pain and translational therapeutic strategies for LBP. The canine IVD, while smaller in size than human, goat, ovine, and bovine IVDs, is larger than most other small animal IVDD models and undergoes maturational changes similar to those of the human IVD. Furthermore, both dogs and humans develop painful IVDD as a spontaneous process, resulting in similar characteristic pathologies and clinical signs. Future exploration of the canine model as a model of IVD-associated spinal pain and biological treatments using the canine clinical model will further demonstrate its translational capabilities with the added ethical benefit of treating an existing veterinary patient population with IVDD.

Acute pain and peripheral sensitization following cautery disbudding in 1- and 4-week-old calves

Acute pain and peripheral sensitization development after cautery disbudding was investigated in 33 calves administered preventive multimodal analgesia. The animals were assigned randomly to three groups: 1) Group SH (Control), undergoing sham disbudding at 1 and 4weeks of age; 2) Group ED (Early Disbudding), undergoing disbudding at 1week of age and sham disbudding at 4weeks of age; 3) Group LD (Late Disbudding), undergoing sham disbudding at 1week of age and disbudding at 4weeks of age. Physiological parameters (heart rate, respiratory rate, rectal temperature, invasive blood pressure, cortisol, β-endorphin, interleukin-1β, interleukin-6, tumor necrosis factor-α and haptoglobin plasmatic concentration), local variables (tactile sensitivity score, pressure pain thresholds and horn temperature), behavior and pain scores [multidimensional pain scale and visual analogue scale (VAS)] were assessed at baseline and at several pre-determined time points until 24h after disbudding. Tactile sensitivity score significantly and equally increased in both groups ED and LD and pressure pain thresholds significantly decreased in group LD until 24h after disbudding compared to group SH. Pain and VAS scores significantly and equally increased in both groups ED and LD until 24h after disbudding compared to group SH. No significant differences in physiological parameters, behavior and horn temperature were detected among groups. The present study suggests that acute pain and peripheral sensitization develop and do not differ in calves disbudded at 1week and 4weeks of age. Moreover, the use of physiological and behavioral parameters as sole indicators of acute pain might lead to improper conclusions and should be reassessed.

Targeting Translational Successes through CANSORT-SCI: Using Pet Dogs To Identify Effective Treatments for Spinal Cord Injury

Translation of therapeutic interventions for spinal cord injury (SCI) from laboratory to clinic has been historically challenging, highlighting the need for robust models of injury that more closely mirror the human condition. The high prevalence of acute, naturally occurring SCI in pet dogs provides a unique opportunity to evaluate expeditiously promising interventions in a population of animals that receive diagnoses and treatment clinically in a manner similar to persons with SCI, while adhering to National Institutes of Health guidelines for scientific rigor and transparent reporting. In addition, pet dogs with chronic paralysis are often maintained long-term by their owners, offering a similarly unique population for study of chronic SCI. Despite this, only a small number of studies have used the clinical dog model of SCI. The Canine Spinal Cord Injury Consortium (CANSORT-SCI) was recently established by a group of veterinarians and basic science researchers to promote the value of the canine clinical model of SCI. The CANSORT-SCI group held an inaugural meeting November 20 and 21, 2015 to evaluate opportunities and challenges to the use of pet dogs in SCI research. Key challenges identified included lack of familiarity with the model among nonveterinary scientists and questions about how and where in the translational process the canine clinical model would be most valuable. In light of these, we review the natural history, outcome, and available assessment tools associated with canine clinical SCI with emphasis on their relevance to human SCI and the translational process.

Development and initial validation of a sensory threshold examination protocol (STEP) for phenotyping canine pain syndromes

OBJECTIVE

To study the feasibility and test-retest repeatability of a sensory threshold examination protocol (STEP) and report the quantitative sensory threshold distributions in healthy dogs.

STUDY DESIGN

Prospective, observational, cohort study.

ANIMALS

Twenty-five healthy client-owned dogs.

METHODS

Tactile sensitivity test (TST) (von Frey filaments), mechanical thresholds (MT with 2, 4 and 8 mm probes), heat thresholds (HT) and responsiveness to cold stimulus (CT at 0 °C) were quantitatively assessed for five body areas (BAs; tibias, humeri, neck, thoracolumbar region and abdomen) in a randomized order on three different occasions. Linear mixed model and generalized linear mixed models were used to evaluate the effects of body weight category, age, sex, BA, occasion, feasibility score and investigator experience. Test-retest repeatability was evaluated with the intra-class correlation coefficient.

RESULTS

The STEP lasted 90 minutes without side effects. The BA affected most tests (p ≤ 0.001). Higher thresholds and longer cold latencies were scored in the neck (p ≤ 0.024) compared to other BAs. Weight category affected all thresholds (p ≤ 0.037). Small dogs had lower MT (∼1.4 N mean difference) and HT (1.1 °C mean difference) than other dogs (p ≤ 0.029). Young dogs had higher HT than adults (2.2 °C mean difference) (p = 0.035). Gender also affected TST, MT and HT (p < 0.05) (females versus males: TST odds ratio = 0.5, MT = 1.3 N mean difference, HT = 2.2 °C mean difference). Repeatability was substantial to moderate for all tests, but poor for TST. There was no difference in thresholds between occasions, except for CT. Test-retest repeatability was slightly better with the 2 mm MT probe compared to other diameters and improved with operator experience.

CONCLUSIONS AND CLINICAL RELEVANCE

The STEP was feasible, was well tolerated and showed substantial test-retest repeatability in healthy dogs. Further validation is needed in dogs suffering pain.

Adaptation of the Basso-Beattie-Bresnahan locomotor rating scale for use in a clinical model of spinal cord injury in dogs

BACKGROUND

Naturally occurring acute spinal cord injury (SCI) in pet dogs provides an important clinical animal model through which to confirm and extend findings from rodent studies; however, validated quantitative outcome measures for dogs are limited.

NEW METHOD

We adapted the Basso Beattie Bresnahan (BBB) scale for use in a clinical dog model of acute thoracolumbar SCI. Based on observation of normal dogs, modifications were made to account for species differences in locomotion. Assessments of paw and tail position, and trunk stability were modified to produce a 19 point scale suitable for use in dogs, termed the canine BBB scale (cBBB). Pet dogs with naturally occurring acute SCI were assigned cBBB scores at 3, 10 and 30days after laminectomy.

RESULTS

Scores assigned via the cBBB were stable across testing sessions in normal dogs but increased significantly between days 3 and 30 in SCI-affected dogs (p=0.0003). The scale was highly responsive to changes in locomotor recovery over a 30day period, with a standardized response mean of 1.34.

COMPARISON WITH EXISTING METHODS

Concurrent validity was good, with strong correlations observed between the cBBB and two other locomotor scales, the OSCIS (r=0.94; p<0.001) and the MFS (r=0.85; p<0.0001). cBBB scores inversely correlated with other assessments of recovery including mechanical sensory threshold (r=-0.68; p<0.0001) and coefficient of variation of stride length (r=-0.49; p<0.0001).

CONCLUSIONS

These results support the use of the cBBB to assess locomotor recovery in canine clinical translational models of SCI.

Managing Neuropathic Pain in Dogs

Disorders of the somatosensory system such as neuropathic pain are common in people with chronic neurologic and musculoskeletal diseases, yet these conditions remain an underappreciated morbidity in veterinary patients. This is likely because assessment of neuropathic pain in people relies heavily on self-reporting, something our veterinary patients are not able to do. The development of neuropathic pain is a complex phenomenon, and concepts related to it are frequently not addressed in the standard veterinary medical curriculum such that veterinarians may not recognize this as a potential problem in patients. The goals of this review are to discuss basic concepts in the pathophysiology of neuropathic pain, provide definitions for common clinical terms used in association with the condition, and discuss pharmacological treatment options for dogs with neuropathic pain. The development of neuropathic pain involves key mechanisms such as ectopic afferent nerve activity, peripheral sensitization, central sensitization, impaired inhibitory modulation, and pathologic activation of microglia. Treatments aimed at reducing neuropathic pain are targeted at one or more of these mechanisms. Several drugs are commonly used in the veterinary clinical setting to treat neuropathic pain. These include gabapentin, pregabalin, amantadine, and amitriptyline. Proposed mechanisms of action for each drug, and known pharmacokinetic profiles in dogs are discussed. Strong evidence exists in the human literature for the utility of most of these treatments, but clinical veterinary-specific literature is currently limited. Future studies should focus on objective methods to document neuropathic pain and monitor response to therapy in veterinary patients.