The lumbosacral junction in working german shepherd dogs -- neurological and radiological evaluation

Qualitative and quantitative computed tomographic characteristics of the lumbosacral spine in German Shepherd military working dogs with versus without lumbosacral pain

Lumbosacral (LS) stenosis is a cause of lower back pain, loss of mission readiness, and early retirement in military working dogs (MWDs). Aims of the present two-part study were to evaluate a sample of German Shepherd MWDs using standard clinical criteria for LS pain, standard qualitative computed tomographic (CT) criteria for LS stenosis, novel quantitative CT criteria for LS stenosis, and novel behavioral classification criteria for LS pain. Data were retrieved from archives of a tertiary referral MWD hospital. Study 1 was a retrospective, observational, two-group design with a hypothesis that there would be a significant difference in the percentage of affected German Shepherd MWDs with multilevel stenosis (affecting ≥ 3 vertebrae) between LS pain groups, based on standard clinical and qualitative CT criteria. Study 2 was a retrospective, observational, cross-sectional, two- and three-group study design with a hypothesis that quantitative CT measurements would significantly differ between LS pain groups, assigned based on 3 classification systems. The 1st classification system used standard clinical criteria, while the 2nd and 3rd novel classifications included behavioral signs of LS pain. The following quantitative CT measures were recorded without knowledge of behavioral classification: vertebral foramen area, vertebral foramen volume, vertebral foramen fat area; and ratios of vertebral foramen area/vertebral body area (foramen area ratio), cranial vertebral foramen area/caudal vertebral foramen area (cranial:caudal foramen area ratio), and vertebral fat area/vertebral body area (fat area ratio). Study 1 findings did not support the hypothesis in that there was no significant difference in the percentage of dogs affected with multilevel stenosis between LS pain groups (P = 0.6567). Findings for study 2 supported the hypothesis in that dogs with LS pain were significantly more affected by multilevel stenosis (P = 0.0273). Significant differences occurred between LS pain groups in select vertebral locations for all measurements (P ≤ 0.05) except vertebral foramen area and vertebral foramen volume (P > 0.05). Comparisons using novel quantitative CT measures and behavioral classification criteria identified significant differences between LS pain groups that were not detected using standard qualitative criteria. These novel quantitative and behavioral classification criteria may be helpful in future research on causes for early retirement in German Shepherd MWDs.

Dynamic MRI is reliable for evaluation of the lumbosacral spine in healthy dogs

Magnetic resonance imaging (MRI) is commonly used to diagnose degenerative lumbosacral stenosis; however, studies show limited correlation between imaging and clinical signs. The purpose of this prospective observer agreement study was to use dynamic MRI of the lumbosacral (LS) spine of healthy dogs to determine reliable reference ranges. Twenty-two healthy large breed dogs were prospectively enrolled. MRI of the LS spine was performed in T2-weighted, T1-weighted, and T2-weighted SPACE sequences in neutral, flexed, and extended positions. Four observers performed image analyses. Measurements included LS angle, vertebral canal height and area, and LS foraminal areas. Ordinal categorical assessment of loss of fat signal in the foramina, LS compression, intervertebral disc (IVD) degeneration, spondylosis, and IVD protrusion was also performed. The majority of values were significantly larger in flexion versus neutral position, and significantly smaller in extension versus neutral position (P < .05). Subclinical compression and IVD protrusion was noted in a neutral position in 45% and 55% of dogs and in an extended position in 85% and 73% of dogs, respectively. Interobserver agreement was strong (intracluster correlation coefficient [ICC] > .5) except for the L7:LS vertebral canal area ratio (ICC ≤ .03). Intraobserver agreement was high (rho > .5) for all measurements except for the mid-L6:LS vertebral canal height ratio (rho = .38). There was poor interobserver agreement for loss of fat signal in the foramina and evidence of compression. This study provides the groundwork for future studies using dynamic MRI to evaluate dogs with signs of clinical LS disease.

Evaluation of L7-S1 nerve root pathology with low-field MRI in dogs with lumbosacral foraminal stenosis

OBJECTIVE

To describe low-field MRI findings associated with lumbosacral foraminal stenosis and radiculopathy and correlate these with clinical signs.

STUDY DESIGN

Retrospective study.

ANIMALS

Client-owned dogs (n = 240) that underwent a clinical examination and standardized MRI protocol of the lumbosacral junction.

METHODS

Medical records of dogs with degenerative lumbosacral stenosis with neurological clinical evaluation and MRI of the lumbosacral junction were used to describe imaging pathologies and relate them to clinical status.

RESULTS

In total, 480 L7 neuroforamina were evaluated. A loss of foraminal fat signal was identified in 364 of 480 neuroforamina of which 87.9% (n=320) showed also concurrent nerve root changes. Magnetic resonance imaging features of L7 radiculopathy included nerve root enlargement and hyperintensity to surrounding connective tissue in dorsal oblique gradient echo short time inversion recovery sequences and specific changes in shape, size, or position of the nerve root in transverse T1-weighted sequences. Radiculopathy was noted as a consequence of either circumferential (entrapment) or focal (impingement) foraminal stenosis. Lateral vertebral spondylotic and intervertebral facet joint changes were the most common underlying spinal and neuroforaminal pathologies. Clinical signs were present in the ipsilateral hind leg in 85% (n = 65) of dogs with unilateral lumbosacral imaging findings.

CONCLUSION

A loss of foraminal fat signal was likely to be associated with L7 radiculopathy and foraminal stenosis. Unilateral lesions were generally associated with clinical signs on the ipsilateral limb.

CLINICAL SIGNIFICANCE

Loss of foraminal fat signal revealed by low-field MRI should prompt the assessment of concurrent radiculopathy and underlying stenosis, and in coherence with clinical findings, when is combined with clinical findings, improves the diagnosis of lumbosacral foraminal stenosis.

Canine Degenerative Lumbosacral Stenosis: Prevalence, Impact And Management Strategies

Canine degenerative lumbosacral stenosis (DLSS) is a syndrome of low back pain with or without neurologic dysfunction associated with compression of the cauda equina. Most commonly occurring in medium- to large-breed dogs of middle to older age, German shepherd and working dogs are predisposed. Diagnosis is based on a combination of clinical signs, advanced imaging and ruling out other differential diagnoses. The volume of the intervertebral foramina at the lumbosacral junction is naturally reduced on extension but degenerative changes lead to a more marked reduction that can impinge the L7 nerve roots. Evidence is lacking on which to base decision-making for treatment of dogs with DLSS. However, surgical intervention may be indicated in dogs that do not respond to conservative management, or for dogs in which there is a requirement to work that prevents lifestyle adjustments. Improvements in electrodiagnosis and novel intra-discal treatments may improve the management of DLSS in the future.

Cauda equina syndrome in dogs - a review

A lesion of sacrococcygeal spinal nerve roots forming a structure that resembles a horse's tail results in the development of clinical entity identified as the cauda equina syndrome (CES). The disease can evolve slowly and symptomatology can be incomplete, but the fully developed CES is characterized by pain and altered sensation in the pelvic extremities, tail, perianogenital region, paresis or plegia of hind limbs, incontinence and impotence. Major causes of CES in dogs are degenerative changes of the lumbosacral vertebral column, haematoma, inflammation, neoplasm or trauma. The diagnosis is based on history, clinical presentation, neurological symptomatology, spinal röntgenography, computed tomography, and magnetic resonance imaging. In animals experiencing initial episodes of CES, conservative therapy can be attempted. But the only rational treatment of patients with severe neurological deficit is surgical decompression of the neural structures. The outcome depends on the underlying aetiology and the degree of sensory, motor and autonomic dysfunction. Canine and porcine experimental models mimicking the CES showed the involvement of intrinsic spinal cord structures. This points out the need for an early diagnosis followed by aggressive management before irreversible neuronal lesions develop. The search strategy involved the PubMed, Medline, Embase and ISI Web of Science from January 2000 to August 2017 using the terms 'cauda equina syndrome' and 'lumbosacral stenosis' in the English language literature; also references from selected papers were scanned and relevant articles included.

Evaluation of the rostral projection of the sacral lamina as a component of degenerative lumbosacral stenosis in German shepherd dogs

OBJECTIVE

To determine the association between a greater rostral projection of the sacral lamina and clinical signs of cauda equina syndrome (CES) in German shepherd dogs (GSD) with presumptive degenerative lumbosacral disease (DLSS).

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

One hundred forty-three GSD (125 police dogs and 18 pet dogs) presenting for either CES or prebreeding evaluation. Fifty-five were classified as affected by CES and diagnosed with DLSS, and 88 were classified as unaffected on the basis of clinical and imaging findings.

METHODS

The position of the rostral edge of the sacral lamina was measured from radiographs and/or computed tomography (CT) scans. This position was compared between affected and unaffected dogs. In dogs that underwent both radiography and CT scanning, the agreement between sacral lamina localization using each imaging modality was determined. Owners/handlers were contacted to determine whether dogs subsequently developed clinical signs compatible with CES at a mean of 29 months (unaffected).

RESULTS

The sacral lamina did not extend as far rostrally in affected dogs, compared to unaffected dogs (P = .04). Among the 88 dogs unaffected by CES at initial evaluation, 2 developed clinical signs consistent with CES at follow-up.

CONCLUSION

Rostral projection of the sacral lamina, previously proposed as a potential risk factor in dogs with CES due to lumbosacral degeneration, was not associated with a diagnosis of DLSS in this study; the opposite was true.

CLINICAL SIGNIFICANCE

Rostral projection of the sacral lamina may not be a predisposing factor in the development of CES due to DLSS in GSD.

Lumbosacral stenosis in Labrador retriever military working dogs - an exomic exploratory study

Background

Canine lumbosacral stenosis is defined as narrowing of the caudal lumbar and/or sacral vertebral canal. A risk factor for neurologic problems in many large sized breeds, lumbosacral stenosis can also cause early retirement in Labrador retriever military working dogs. Though vital for conservative management of the condition, early detection is complicated by the ambiguous nature of clinical signs of lumbosacral stenosis in stoic and high-drive Labrador retriever military working dogs. Though clinical diagnoses of lumbosacral stenosis using CT imaging are standard, they are usually not performed unless dogs present with clinical symptoms. Understanding the underlying genomic mechanisms would be beneficial in developing early detection methods for lumbosacral stenosis, which could prevent premature retirement in working dogs. The exomes of 8 young Labrador retriever military working dogs (4 affected and 4 unaffected by lumbosacral stenosis, phenotypically selected by CT image analyses from 40 dogs with no reported clinical signs of the condition) were sequenced to identify and annotate exonic variants between dogs negative and positive for lumbosacral stenosis.

Results

Two-hundred and fifty-two variants were detected to be homozygous for the wild allele and either homozygous or heterozygous for the variant allele. Seventeen non-disruptive variants were detected that could affect protein effectiveness in 7 annotated (SCN1B, RGS9BP, ASXL3, TTR, LRRC16B, PTPRO, ZBBX) and 3 predicted genes (EEF1A1, DNAJA1, ZFX). No exonic variants were detected in any of the canine orthologues for human lumbar spinal stenosis candidate genes.

Conclusions

TTR (transthyretin) gene could be a possible candidate for lumbosacral stenosis in Labrador retrievers based on previous human studies that have reported an association between human lumbar spinal stenosis and transthyretin protein amyloidosis. Other genes identified with exonic variants in this study but with no known published association with lumbosacral stenosis and/or lumbar spinal stenosis could also be candidate genes for future canine lumbosacral stenosis studies but their roles remain currently unknown. Human lumbar spinal stenosis candidate genes also cannot be ruled out as lumbosacral stenosis candidate genes. More definitive genetic investigations of this condition are needed before any genetic test for lumbosacral stenosis in Labrador retriever can be developed.

Electronic supplementary material

The online version of this article (10.1186/s40575-017-0052-6) contains supplementary material, which is available to authorized users.

Estudo radiográfico da articulação lombossacra em cães das raças Pastor Alemão, Rottweiler e Doberman

Este trabalho teve como objetivo avaliar a variação entre diferentes raças das medidas radiográficas da articulação lombossacra. Foram utilizados 20 cães da raça Pastor Alemão, 20 cães da raça Rottweiler e 20 da raça Doberman. A articulação lombossacra foi avaliada radiograficamente com os membros pélvicos em posição neutra (N), em ventroflexão (VF) e dorsoextensão (DE). Foram mensurados os ângulos entre os processos articulares de L7 e S1 (PA), entre as epífises distal de L7 e proximal de S1 (EPIF), o ângulo lombossacro (LS), a amplitude de movimento (ROM) desses ângulos, o ponto de interseção das retas que formam esses ângulos e a respectiva ROM. Os resultados mostraram que a altura do canal vertebral em L7 é menor no Pastor Alemão (9,5mm) e maior no Rottweiler (10,5mm). O EPIF-DE foi maior no Pastor Alemão (38,03º). O PA-N foi menor no Pastor Alemão (15,98º). O LS-VF foi menor no Doberman (170,01º), e não diferiu entre o Pastor Alemão (179,17º) e o Rottweiler (176,61º). Os cães Pastores Alemães demonstraram uma maior ROM dos ângulos EPIF e LS. Concluiu-se que cães da raça Pastor Alemão apresentam maior instabilidade dessa articulação em relação às outras duas raças estudadas.

Effect of analgesic therapy on clinical outcome measures in a randomized controlled trial using client-owned dogs with hip osteoarthritis

Background

Pain and impaired mobility because of osteoarthritis (OA) is common in dogs and humans. Efficacy studies of analgesic drug treatment of dogs with naturally occurring OA may be challenging, as a caregiver placebo effect is typically evident. However, little is known about effect sizes of common outcome-measures in canine clinical trials evaluating treatment of OA pain. Forty-nine client-owned dogs with hip OA were enrolled in a randomized, double-blinded placebo-controlled prospective trial. After a 1 week baseline period, dogs were randomly assigned to a treatment (ABT-116 – transient receptor potential vanilloid 1 (TRPV1) antagonist, Carprofen – non-steroidal anti-inflammatory drug (NSAID), Tramadol - synthetic opiate, or Placebo) for 2 weeks. Outcome-measures included physical examination parameters, owner questionnaire, activity monitoring, gait analysis, and use of rescue medication.

Results

Acute hyperthermia developed after ABT-116 treatment (P < 0.001). Treatment with carprofen (P ≤ 0.01) and tramadol (P ≤ 0.001) led to improved mobility assessed by owner questionnaire. Nighttime activity was increased after ABT-116 treatment (P = 0.01). Kinetic gait analysis did not reveal significant treatment effects. Use of rescue treatment decreased with treatment in the ABT-116 and Carprofen groups (P < 0.001). Questionnaire score and activity count at the end of treatment were correlated with age, clinical severity at trial entry, and outcome measure baseline status (S_R ≥ ±0.40, P ≤ 0.005). Placebo treatment effects were evident with all variables studied.

Conclusion

Treatment of hip OA in client-owned dogs is associated with a placebo effect for all variables that are commonly used for efficacy studies of analgesic drugs. This likely reflects caregiver bias or the phenomenon of regression to the mean. In the present study, outcome measures with significant effects also varied between groups, highlighting the value of using multiple outcome measures, as well as an a priori analysis of effect size associated with each measure. Effect size data from the present study could be used to inform design of future trials studying analgesic treatment of canine OA. Our results suggest that analgesic treatment with ABT-116 is not as effective as carprofen or tramadol for treatment of hip arthritis pain in client-owned dogs.

Transarticular facet screw stabilization and dorsal laminectomy in 26 dogs with degenerative lumbosacral stenosis with instability

OBJECTIVE

To describe outcome after transarticular facet screw stabilization and dorsal laminectomy for treatment of dynamic degenerative lumbosacral stenosis (DLS) in 26 dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n = 26) with dynamic DLS.

METHODS

Medical records (2004-2009) of dogs treated with transarticular facet screw stabilization and dorsal laminectomy were reviewed. Dogs (n = 26) were available for immediate postoperative follow-up, 21 dogs at 6 weeks, and 15 at greater than 6 months. Dogs were evaluated by radiographic assessment and owner questionnaire. Lumbosacral (LS) intervertebral disc (IVD) spaces were measured on pre and postoperative 6-week and 6-month radiographs.

RESULTS

In 23 dogs, improvement in clinical signs occurred within 7 days of surgery. Overall postsurgical complication rate directly related to the surgical procedure was 15.4%. LS IVD space measurements taken immediately postoperatively, at 6 weeks, and ≥ 6 months were all significantly increased compared with preoperative measurements. All working dogs (4) returned to full work within 14 months. Most owners (85%) reported their dog was ambulating normally at 6 months with no perceptible lameness during normal activity. All owners perceived their dog's ability to walk, run, and jump after surgery to be improved.

CONCLUSIONS

Transarticular facet screw stabilization and dorsal laminectomy maintains distraction of the LS IVD space for medium-to-large breed dogs with dynamic DLS with a high degree of owner satisfaction, and is comparable to other reported surgical techniques for DLS.

MR-imaging of lumbosacral intervertebral disc degeneration in clinically sound German shepherd dogs compared to other breeds

German shepherd dogs are overrepresented in the group of dogs with cauda equina compression syndrome due to degenerative lumbosacral stenosis. A congenital predisposition for early degeneration of the lumbosacral intervertebral disc has been suspected. Our aims were to assess the morphologic appearance of the lumbosacral intervertebral disc and the lumbosacral junction in healthy German shepherd dogs compared to other breeds and to evaluate for an early onset of degenerative changes. The lumbosacral spine of 110 clinically sound German shepherd dogs and 47 healthy dogs of other large breeds was examined using magnetic resonance (MR) imaging. The degeneration of every intervertebral disc was graded using an established classification system. Signal intensity of the entire lumbosacral disc and the nucleus pulposus was determined independently. Lumbosacral malalignment was assessed according to a previously described method. The findings for the German shepherd dogs were compared to those of the other breeds. Although most dogs were younger than 18 months at the date of examination, significantly higher grades of degeneration were detected for the lumbosacral intervertebral disc of German shepherd dogs (P < 0.003). Degeneration of the lumbosacral intervertebral disc was independent from findings in the other lumbar discs. We conclude that the German shepherd dog has a predisposition for degenerative changes in the lumbosacral intervertebral disc.

A LUMBOSACRAL TRANSITIONAL VERTEBRA IN THE DOG PREDISPOSES TO CAUDA EQUINA SYNDROME

The association between the occurrence of a lumbosacral transitional vertebra (LTV) and the cauda equina syndrome (CES) in dogs was investigated. In 4000 control dogs without signs of CES, 3.5% had an LTV, while in 92 dogs with CES, 16.3% had an LTV. The lesion causing CES always occurred between the last true lumbar vertebra and the LTV. Dogs with an LTV were eight times more likely to develop CES than dogs without an LTV. German Shepherd dogs were eight times more likely to develop CES compared with other breeds. Male dogs were twice as likely to develop CES than females. Dogs with an LTV develop CES 1-2 years earlier than dogs without an LTV.