COMPARISON OF MAGNETIC RESONANCE IMAGING AND MYELOGRAPHY IN 18 DOBERMAN PINSCHER DOGS WITH CERVICAL SPONDYLOMYELOPATHY

Cervical intervertebral disc disease in 307 small-breed dogs (2000-2021): Breed-characteristic features and disc-associated vertebral instability

OBJECTIVE

To evaluate the breed-characteristic features of cervical intervertebral disc disease (C-IVDD) and associated vertebral instability in small-breed dogs and to present the concept of intervertebral disc degeneration and associated instability stage, method of diagnosis, treatment and outcomes.

ANIMALS

In total, 307 client-owned dogs with C-IVDD treated with spinal cord decompression with or without vertebral stabilization (2000-2021).

METHODS

Information on age, sex, affected sites, stabilized sites, diagnostic methods for vertebral instability and outcomes were retrieved. The patient's age, affected sites (cranial vs caudal discs), and frequency of vertebral stabilization were compared in six CD and five NCD breed. Multivariable analyses of the chondrodystrophic (CD) vs non-CD (NCD) groups, and vertebral stabilization (dogs stabilized vs dogs not stabilized) were performed.

RESULTS

In total, 222 (72.3%) and 77 (25.1%) were CD and NCD breeds, respectively. Vertebral instabilities were diagnosed based on the survey radiographs with computed tomography/magnetic resonance imaging (n = 2), dynamic myelography (n = 29), intraoperative spinal manipulation (n = 11) or second surgery in dogs with persistent postoperative paraspinal pain (n = 3). Of these dogs, 295 (96.1%) recovered (median follow-up: 8.5 [range, 1-119] months). Significant differences in age, affected sites and frequency of stabilization were noted among the breeds. Older age and frequent vertebral stabilization were the associated factors for the NCD breed dogs. Male dogs, caudal discs affected (C5-T1) and the NCD breed dogs were risk factors for the dogs with vertebral stabilization.

CONCLUSION

Vertebral stabilization is indicated for small-breed dogs with cervical disc-associated vertebral instability.

Morphometric Evaluation of Thoracolumbar Spinal Canal and Cord by Magnetic Resonance Imaging in Normal Small-Breed Dogs

Thoracolumbar intervertebral disc disease (IVDD) is the most common cause of spinal injury in dogs. MRI has been considered the gold standard for neurologic diagnosis, but studies focusing on the thoracolumbar spinal canal and spinal cord using MRI in small-breed dogs are limited. Therefore, this study aimed to establish an MRI reference range for the spinal cord and canal measurements (height, width, cord-to-canal ratio of height, width, cross-sectional area (CSA)) of each intervertebral disc level from T11 to L5 (total of seven levels) on transverse T2-weighted images in normal small-breed dogs. We hypothesized that the spinal cord and spinal canal measurements might vary according to the body weight and age. The width and height of the spinal cord and canal increased as the body weight increased at all levels (p < 0.05). The cord-to-canal ratio of the width showed a negative correlation to the body weight at all levels. The cord-to-canal ratio of the height did not show any correlation to the body weight at all levels. All measurements (height, width, cord-to-canal ratio of height, width, CSA) did not show any statistical correlation between the groups subdivided by age. These measurements could serve as a morphometric baseline for thoracolumbar spinal diseases and clinical research in small-breed dogs.

Clinical and imaging findings in dogs with nerve root signature associated with cervical intervertebral disc herniation

BACKGROUND

Intervertebral disc herniation (IVDH) is the most common spinal cord disease in dogs. Little information is available regarding the clinical presentation of nerve root signature (NRS) associated with cervical IVDH.

HYPOTHESIS/OBJECTIVE

To detail the clinical and magnetic resonance imaging (MRI) findings in dogs with NRS associated with cervical IVDH.

ANIMALS

Forty-seven client-owned dogs presenting with thoracic limb NRS and MRI confirmed IVDH.

METHODS

Medical records from 2010 to 2020 were retrospectively reviewed for dogs that met inclusion criteria. Imaging studies were evaluated by 2 individuals to characterize location and severity of neural tissue compression.

RESULTS

Chondrodystrophoid dogs comprised the majority of the study cohort, with dachshund the most common breed (n = 10). Three-quarters of dogs were ≥7 years of age. Interobserver agreement was moderate or good for all of the imaging variables evaluated. The C6-C7 intervertebral disc space was significantly overrepresented (P = .01), comprising 32% (15/47) of the affected discs. However, 42% (20/47) of cases involved C2-C3 though C4-C5 disc sites. Disc material was more frequently located laterally compared to medially within the vertebral canal (P = .0005), and to be associated with compression of the nerve root at the level of the intervertebral foramen (P = .012).

CONCLUSION/CLINICAL IMPORTANCE

NRS is most commonly associated with lateralized or foraminal cervical disc herniations. It is most prevalent with C6-C7 intervertebral disc involvement, suggesting that there might be unique anatomic factors that contribute to development of NRS at this site, but can be a clinical manifestation of IVDH occurring anywhere along the cervical spine.

Comparison of Two Surgical Techniques for the Treatment of Canine Disc Associated-Cervical Spondylomyelopathy

Objective

To compare prosthetic disc and vertebral distraction stabilization in dogs with disc-associated cervical spondylomyelopathy (DA-CSM).

Study Design

A retrospective clinical study.

Animals

25 dogs.

Methods

Dogs presenting with clinical signs and MRI findings compatible with DA-CSM underwent surgery. Implantation of the Adamo's prosthetic disc (PD) or vertebral distraction-stabilization (DS) with intervertebral cage, ventral locking plates, and dorsal transarticular screws was performed. All dogs were followed-up and evaluated clinically for a minimum of 1 year and radiographically for at least 3 months. In particular, we focused on the evaluation of subsidence (the degree of vertebral collapse).

Results

Twenty-five dogs were enrolled: 12 with PD implantation and 13 with DS implantation. Of these, 24 dogs were followed-up at 1 year. Overall, 12 dogs improved (4 PD and 8 DS), eight were stable (4 PD and 4 DS), and four deteriorated (3 PD and 1 DS). Deterioration was more common in PD cases, especially soon after surgery. In a few PD cases, a second surgery was necessary. The most common complication in dogs with DS was discospondylitis. Subsidence was detected in 11 PD and 7 DS dogs. Subsidence was more severe and occurred sooner after surgery in PD cases compared to DS cases. DS cases were more prone to clinical improvement and less prone to subsidence than PD cases in this study. However, the statistical evidence was weak owing to the small sample size.

Conclusion

The preliminary results suggest that prosthetic disc implantation is more prone to clinical and radiographic failures than distraction stabilization.

Clinical Relevance

The DS technique is a valuable surgical option for treating dogs with DA-CSM, with favorable short- and long-term clinical and radiographic outcomes.

Clinical and diagnostic imaging findings in a bengal tiger (Panthera tigris tigris) with cervical spondylomyelopathy: A case report

An adult neutered male Bengal tiger (Panthera tigris tigris) presented with abnormal gait. Neurological examination showed poor left ambulatory hemiparesis, spontaneous proprioceptive deficit in the left anterior limb, and decreased flexor reflex in the forelimbs. The neurological symptoms suggested a caudal cervical spinal cord lesion. Pathological findings included increased cholinesterase and protein levels in the cerebrospinal fluid. Computed tomography examination revealed C2-C3 intervertebral disc herniation, C5-C6 intervertebral disc herniation associated with a reduction of the intervertebral space, and mild ventral dislocation of the C6 vertebra compared to C5. In addition, severe bilateral shoulder osteoarthritis and a hypoattenuating nodule in the left thyroid gland with an open etiology were observed. These findings were interpreted as indicating cervical spondylomyelopathy (CSM). Treatment included analgesic and steroidal anti-inflammatory therapy as well as movement restriction. Follow-up at 4 weeks showed modest improvement. Thus, CSM should be included in the differential diagnosis of tigers with neurological cervical signs.

Computed tomographic examination of the articular process joints of the cervical spine in warmblood horses: 86 cases (2015-2017)

OBJECTIVE

To describe articular process joints (APJs) of the cervical spine in horses on the basis of CT and to determine whether abnormalities were associated with clinical signs.

ANIMALS

86 client-owned warmblood horses.

PROCEDURES

Horses that underwent CT of the cervical spine between January 2015 and January 2017 were eligible for study inclusion. Medical records were reviewed for age, body weight, breed, sex, history, clinical signs, and CT findings. Horses were divided into 3 case groups and 1 control group on the basis of clinical signs.

RESULTS

70 warmblood horses were cases, and 16 were controls. Abnormalities were more frequent from C5 through T1 and were severe in only horses from the case group. Narrowing of the intervertebral foramen was common in horses in the case group (85.7%), often owing to enlarged, misshaped articular processes, followed by degenerative changes, periarticular osteolysis, cyst-like lesions, and fragmentation. High articular process-to-vertebral body (C6) ratio (APBR) and high-grade narrowing of the intervertebral foramen and periarticular osteolysis were noted for horses with forelimb lameness or signs of cervical pain or stiffness. No association was identified between APBR and age or sex. An APBR > 1.5 was found in only horses in the case group, and 32.3% of APJs with APBRs > 1.5 did not have any degenerative changes and periarticular osteolysis.

CONCLUSIONS AND CLINICAL RELEVANCE

CT was useful to identify abnormalities of the APJs of the cervical spine. An association existed between CT findings and clinical signs. The APJs can be enlarged without concurrent degenerative changes.

Neurologic Causes of Thoracic Limb Lameness

Although lameness of the thoracic limb typically is due to orthopedic disease, there are several important neurologic conditions that result in lameness. Neurologic diseases cause lameness due to disease of the nerves, nerve roots, spinal cord, or muscles. Common differentials include lateralized intervertebral disc extrusions, caudal cervical spondylomyelopathy (wobbler disease), brachial plexus avulsion, neuritis, and peripheral nerve sheath tumors. Many of these diseases compress or destroy the nerve roots of the cervical intumescence, resulting in non-weight-bearing lameness, or root signature. Advanced diagnostics, such as magnetic resonance imaging, are necessary in these cases to determine the underlying cause.

CT myelographic diagnosis of ligamentum flavum hypertrophy in a Warmblood Gelding with progressive ataxia

An 8-year-old Warmblood gelding presented with a history of progressive ataxia for 6 weeks. Intra- and intervertebral ratios measured from lateral radiographs of the cervical spine were within normal limits. Computed tomographic myelography of the cervical spine revealed focal compression of the dorsal and the ventral contrast column as well as a ventral displacement of the spinal cord within the spinal canal due to a bulging of soft tissue attenuating material in the dorsal half of the intervertebral junction of C6 and C7. Post-mortem histopathological examination confirmed chondroid metaplasia of the ligamentum flavum at C6-C7.

Surgical management and long-term outcome of dogs with cervical spondylomyelopathy with an anchored intervertebral titanium device

OBJECTIVE

To assess the short- and long-term outcome of an anchored intervertebral titanium device (C-LOX) for the treatment of 10 dogs with disc-associated cervical spondylomyelopathy (DACSM) and 1 dog with osseous-associated cervical spondylomyelopathy.

DESIGN

Retrospective case series.

METHODS

Dogs were included if they were diagnosed with either DACSM or osseous-associated cervical spondylomyelopathy via myelography with or without advanced imaging and underwent surgical distraction and stabilisation of the affected intervertebral disc with a C-LOX implant. Assessment included short-term neurological outcome, radiography immediately and 6 weeks' postsurgery, owner questionnaire and veterinary clinical assessment.

RESULTS

The mean follow-up time was 12 months. Improvement in neurological status was noted in 10 of 11 dogs. Screw loosening or subsidence occurred in five dogs. Revision surgery was performed in two dogs due to implant fracture (n = 1) and recurrence of spinal cord compression due to endplate subsidence around the implant (n = 1). Adjacent segment disease occurred in three dogs (30%) with DACSM at a mean of 11 months postsurgery.

CONCLUSION

The use of the C-LOX implant for dogs with cervical spondylomyelopathy resulted in a high rate of initial neurological improvement; however, there is a moderate incidence of minor and major complications that is comparable to previously described distraction-stabilisation techniques.

Canine Snake-Eye Myelopathy: Clinical, Magnetic Resonance Imaging, and Pathologic Findings in Four Cases

Intramedullary signal change (ISC) is a non-specific finding that is frequently observed on magnetic resonance imaging (MRI) examinations of the canine spinal cord. ISC can represent a variety of primary pathological processes such as neoplasms or myelitides or secondary changes such as edema, cysts, gliosis, or myelomalacia. An unusual phenotype of ISC is the “snake-eye” myelopathy (SEM), which refers to bilaterally symmetric T2 hyperintensities preferentially affecting the ventral horn gray matter on transverse MR images, which resemble a pair of snake's eyes. The pathophysiology of SEM is poorly understood in humans, and this imaging finding may be associated with cervical spondylotic myelopathy, spinal cord ischemia, ossification of the posterior longitudinal ligament, amyotrophic lateral sclerosis, and Hirayama disease. Here we describe four dogs with cervical MRI examinations consistent with an SEM-like phenotype. All dogs initially presented with a central cord syndrome or tetraparesis referable to a C6-T2 neuroanatomic localization, which was attributed to disc-associated spinal cord compression in three cases, while one dog had the SEM-like phenotype with no identifiable etiology. Once the SEM-like phenotype was present on MRI examinations, dogs demonstrated insidious clinical deterioration despite therapeutic interventions. Deterioration was characterized by lower motor neuron weakness and neurogenic muscle atrophy progressing to paralysis in the thoracic limbs, while neurological functions caudal to the level of the SEM-like lesion remained largely preserved for months to years thereafter. Neuropathological features of the SEM-like phenotype include multisegmental cavitations and poliomyelomalacia of laminae VI-IX of the caudal cervical spinal cord, although the lesion evolved into pan-necrosis of gray matter with extension into the adjacent white matter in one case with an 8 years history of progressive disease. Although the pathophysiology of SEM remains unknown, the topographical distribution and appearance of lesions is suggestive of a vascular disorder. As the SEM-like phenotype was uniformly characterized by longitudinally and circumferentially extensive neuronal necrosis, results of this small case series indicate that dogs with clinical signs of central cord syndrome and the SEM-like phenotype involving the cervicothoracic intumescence on MR examinations have a poor prognosis for the preservation or recovery of thoracic limb motor function.

Kinetic and kinematic follow-up gait analysis in Doberman Pinschers with cervical spondylomyelopathy treated medically and surgically

Background

The efficacy of treatment of dogs with cervical spondylomyelopathy (CSM) is commonly based on the owner's and clinician's perception of the gait, which is highly subjective and suffers from observer bias.

Hypothesis/Objectives

To compare selected kinetic and kinematic parameters before and after treatments and to correlate the findings of gait analysis to clinical outcome.

Animals

Eight Doberman Pinschers with CSM confirmed by magnetic resonsance imaging.

Methods

Patients were prospectively studied and treated with either medical management (n = 5) or surgery (n = 3). Force plate analysis and 3‐D kinematic motion capture were performed at initial presentation and approximately 8 weeks later. Force plate parameters evaluated included peak vertical force (PVF). Kinematic parameters measured included number of pelvic limb strides, stifle flexion and extension, maximum and minimum thoracic limb distance, truncal sway, and thoracic limb stride duration.

Results

Kinematic analysis showed that deviation of the spine to the right (truncal sway) was significantly smaller (P < .001) and the degree of right stifle flexion was significantly larger (P = .029) after treatment. Force plate analysis indicated that PVF was significantly different after treatment (P = .049) and the difference of the PVF also was significantly larger (P = .027). However, no correlation was found with either method of gait analysis and clinical recovery.

Conclusions and Clinical Importance

Kinetic and kinematic gait analysis were able to detect differences in dogs with CSM before and after treatment. A correlation of gait analysis to clinical improvement could not be determined.

Cement plug technique for the management of disc-associated cervical spondylopathy in 52 Dobermann Pinscher dogs

Objectives: To report the radiographic and clinical outcome of an intervertebral bone cement plug technique for the management of disc-associated cervical spondylopathy in Dobermann Pinscher dogs.

Methods: Retrospective study of 52 Dobermann Pinscher dogs.

Results: A variable degree of cement plug subsidence with loss of vertebral distraction was evident in all dogs (n = 40) that were radiographed >6 weeks postoperatively. In no case was there definitive evidence of vertebral body fusion. Eight dogs had a sudden deterioration in neurological status, cervical hyperaesthesia, or both between three days and 12 weeks following surgery that was considered to be implant-associated; six of these dogs were euthanatized. Following surgery, 43/52 dogs were considered to be neurologically normal or to have improved, however, nine of 43 subsequently deteriorated due to adjacent segment disease. At the long-term follow-up, 34 dogs were considered to be neurologically normal or to have improved. Twenty-nine dogs were dead by the end of the study period.

Clinical significance: Intervertebral bone cement plug surgery results in an initial improvement in clinical signs in the majority of Dobermann Pinschers with disc-associated cervical spondylopathy. However, it fails to maintain vertebral distraction or achieve vertebral body fusion, and is associated with acute implant complications, additional cervical disc protrusions or mortality in a significant proportion of cases.

Online Supplementary Material: Please note that online supplementary material for this paper is available at: http://dx.doi.org/10.3415/VCOT-15-09-0160.

Comparison of medical and surgical treatment for acute cervical compressive hydrated nucleus pulposus extrusion in dogs

Although successful outcomes have been reported after medical and surgical treatment for dogs with cervical hydrated nucleus pulposus extrusion (HNPE), it is unknown which treatment option is preferred. Thirty-four dogs treated medically (n=18) or surgically (n=16) for cervical HNPE were retrospectively identified. Signalment, clinical presentation and imaging findings were compared between medically and surgically treated dogs. Medical management consisted of restricted exercise in combination with physiotherapy. Surgical treatment consisted of a ventral slot procedure. Short-term follow-up information was retrieved from re-examination visits. Long-term outcome was obtained via telephone interviews. More dogs in the surgical group demonstrated cervical hyperaesthesia on initial clinical presentation (P=0.045), otherwise there was no significant difference in signalment, clinical presentation or imaging findings between both groups. Two dogs in the medically managed group underwent surgical decompression due to an unsatisfactory response to medical management. All cases for which long-term information was available (n=30) were neurologically normal at the time of data collection. There were no significant differences for any of the short-term or long-term outcome variables between both treatment groups. This study demonstrated successful outcomes after medical or surgical treatment and suggests that both treatment modalities can be considered for dogs with cervical HNPE.

Magnetic resonance imaging susceptibility artifacts in the cervical vertebrae and spinal cord related to monocortical screw-polymethylmethacrylate implants in canine cadavers

OBJECTIVE To characterize and compare MRI susceptibility artifacts related to titanium and stainless steel monocortical screws in the cervical vertebrae and spinal cord of canine cadavers. SAMPLE 12 canine cadavers. PROCEDURES Cervical vertebrae (C4 and C5) were surgically stabilized with titanium or stainless steel monocortical screws and polymethylmethacrylate. Routine T1-weighted, T2-weighted, and short tau inversion recovery sequences were performed at 3.0 T. Magnetic susceptibility artifacts in 20 regions of interest (ROIs) across 4 contiguous vertebrae (C3 through C6) were scored by use of an established scoring system. RESULTS Artifact scores for stainless steel screws were significantly greater than scores for titanium screws at 18 of 20 ROIs. Artifact scores for titanium screws were significantly higher for spinal cord ROIs within the implanted vertebrae. Artifact scores for stainless steel screws at C3 were significantly less than at the other 3 cervical vertebrae. CONCLUSIONS AND CLINICAL RELEVANCE Evaluation of routine MRI sequences obtained at 3.0 T revealed that susceptibility artifacts related to titanium monocortical screws were considered mild and should not hinder the overall clinical assessment of the cervical vertebrae and spinal cord. However, mild focal artifacts may obscure small portions of the spinal cord or intervertebral discs immediately adjacent to titanium screws. Severe artifacts related to stainless steel screws were more likely to result in routine MRI sequences being nondiagnostic; however, artifacts may be mitigated by implant positioning.

Kinematic Magnetic Resonance Imaging for Evaluation of Disc-Associated Cervical Spondylomyelopathy in Doberman Pinschers

BACKGROUND

The dynamic component of disc-associated cervical spondylomyelopathy (DA-CSM) currently is evaluated using traction magnetic resonance imaging (MRI), which does not assess changes in flexion and extension of the cervical vertebral column. In humans with cervical spondylotic myelopathy, kinematic MRI is used to identify dynamic compressions.

HYPOTHESIS/OBJECTIVES

To evaluate the feasibility and utility of kMRI in Doberman Pinschers with DA-CSM using a novel positioning device. We hypothesized that kMRI would identify compressive lesions not observed with neutral positioning and change the dimensions of the spinal cord and cervical vertebral canal.

ANIMALS

Nine client-owned Doberman Pinschers with DA-CSM.

METHODS

Prospective study. After standard MR imaging of the cervical spine confirmed DA-CSM, dogs were placed on a positioning device to allow imaging in flexion and extension. Morphologic and morphometric assessments were compared between neutral, flexion, and extension images.

RESULTS

Flexion was associated with improvement or resolution of spinal cord compression in 4/9 patients, whereas extension caused worsening of compressions in 6/9 patients. Extension identified 6 new compressive lesions and was significantly associated with dorsal and ventral compression at C5-C6 (P = .021) and C6-C7 (P = .031). A significant decrease in spinal cord height occurred at C6-C7 from neutral to extension (P = .003) and in vertebral canal height at C5-C6 and C6-C7 from neutral to extension (P = .011 and .017, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results suggest that kMRI is feasible and provides additional information beyond what is observed with neutral imaging, primarily when using extension views, in dogs with DA-CSM.

Magnetic resonance imaging features of Great Danes with and without clinical signs of cervical spondylomyelopathy

OBJECTIVE

To characterize and compare the MRI morphological features of the cervical vertebral column of Great Danes with and without clinical signs of cervical spondylomyelopathy (CSM).

DESIGN

Prospective cohort study.

ANIMALS

30 Great Danes (15 clinically normal and 15 CSM-affected).

PROCEDURES

All dogs underwent MRI of the cervical vertebral column (C2-3 through T1-2). Features evaluated included sites of subarachnoid space compression, spinal cord compression, or both; degree, cause, and direction of compression; MRI signal changes of the spinal cord; articular process (facet) joint characteristics; internal vertebral venous plexus visibility; and presence of extradural synovial cysts as well as presence and degree of intervertebral disk degeneration and foraminal stenosis.

RESULTS

Clinically normal and CSM-affected dogs had 11 and 61 compressive sites, respectively, detected with MRI. All CSM-affected dogs had ≥ 1 site of spinal cord compression. No signal changes were observed in spinal cords of normal dogs, whereas 14 sites of hyperintensity were found in 9 CSM-affected dogs. Foraminal stenosis was present in 11 clinically normal and all CSM-affected dogs. The number of stenotic foraminal sites was significantly greater in the CSM-affected group, and severe stenosis appeared to be more common in this group than in the clinically normal group. Significant differences were identified between clinically normal and CSM-affected dogs with regard to amount of synovial fluid evident, regularity of articular surfaces, degree of articular process joint proliferation, and internal vertebral venous plexus visibility.

CONCLUSIONS AND CLINICAL RELEVANCE

Abnormalities were detected with MRI in several clinically normal Great Danes. Severe spinal cord compression, number of stenotic foraminal sites, and signal changes within the spinal cord distinguished CSM-affected from clinically normal Great Danes.

Evaluation of traditional and novel radiographic vertebral ratios in Great Danes with versus without cervical spondylomyelopathy

Great Danes are predisposed to osseous-associated cervical spondylomyelopathy (Wobbler syndrome). The first aim of this prospective study was to compare values measured using previously published intravertebral and intervertebral ratio methods and a novel ventrodorsal ratio method in radiographs of clinically normal and affected Great Danes. The second aim was to determine whether these ratios could be used as predictors of sites of spinal cord compression based on magnetic resonance imaging (MRI). Thirty dogs (15 normal, 15 affected) were prospectively enrolled. Lateral and ventrodorsal radiographs were obtained and six measurements were recorded from C3-T1. For each vertebral location, intravertebral ratios and intervertebral ratios were calculated from lateral views, and the ratio of the distance between the articular process joints vs. vertebral body width (novel ventrodorsal ratio) was calculated from ventrodorsal views. Values for these three ratios were compared, by vertebral location and dog group. Intravertebral and intervertebral ratios did not differ between dog groups. The ventrodorsal ratio was significantly smaller in affected Great Danes at C5-6 (P = 0.005) and C6-7 (P < 0.001). The ventrodorsal ratio was significantly associated with MRI presence of spinal cord compression. For each 0.1 unit increase in this ratio value, there was a 65% decrease in the odds of spinal cord compression being present at that site, independent of vertebral location (P = 0.002). Findings from this study supported use of the novel ventrodorsal ratio as an initial radiographic screening method for Great Danes with suspected cervical spondylomyelopathy.

Comparison of noncontrast computed tomography and high-field magnetic resonance imaging in the evaluation of Great Danes with cervical spondylomyelopathy

Computed tomography (CT) provides excellent bony detail, whereas magnetic resonance (MR) imaging is superior in evaluating the neural structures. The purpose of this prospective study was to assess interobserver and intermethod agreement in the evaluation of cervical vertebral column morphology and lesion severity in Great Danes with cervical spondylomyelopathy by use of noncontrast CT and high-field MR imaging. Fifteen client-owned affected Great Danes were enrolled. All dogs underwent noncontrast CT under sedation and MR imaging under general anesthesia of the cervical vertebral column. Three observers independently evaluated the images to determine the main site of spinal cord compression, direction and cause of the compression, articular process joint characteristics, and presence of foraminal stenosis. Overall intermethod agreement, intermethod agreement for each observer, overall interobserver agreement, and interobserver agreement between pairs of observers were calculated by use of kappa (κ) statistics. The highest overall intermethod agreements were obtained for the main site of compression and direction of compression with substantial agreements (κ = 0.65 and 0.62, respectively), whereas the lowest was obtained for right-sided foraminal stenosis (κ = 0.39, fair agreement). For both imaging techniques, the highest and lowest interobserver agreements were recorded for the main site of compression and degree of articular joint proliferation, respectively. While different observers frequently agree on the main site of compression using both imaging techniques, there is considerable variation between modalities and among observers when assessing articular process characteristics and foraminal stenosis. Caution should be exerted when comparing image interpretations from multiple observers.

The effect of intervertebral cartilage on neutral posture and range of motion in the necks of sauropod dinosaurs

The necks of sauropod dinosaurs were a key factor in their evolution. The habitual posture and range of motion of these necks has been controversial, and computer-aided studies have argued for an obligatory sub-horizontal pose. However, such studies are compromised by their failure to take into account the important role of intervertebral cartilage. This cartilage takes very different forms in different animals. Mammals and crocodilians have intervertebral discs, while birds have synovial joints in their necks. The form and thickness of cartilage varies significantly even among closely related taxa. We cannot yet tell whether the neck joints of sauropods more closely resembled those of birds or mammals. Inspection of CT scans showed cartilage:bone ratios of 4.5% for Sauroposeidon and about 20% and 15% for two juvenile Apatosaurus individuals. In extant animals, this ratio varied from 2.59% for the rhea to 24% for a juvenile giraffe. It is not yet possible to disentangle ontogenetic and taxonomic signals, but mammal cartilage is generally three times as thick as that of birds. Our most detailed work, on a turkey, yielded a cartilage:bone ratio of 4.56%. Articular cartilage also added 11% to the length of the turkey's zygapophyseal facets. Simple image manipulation suggests that incorporating 4.56% of neck cartilage into an intervertebral joint of a turkey raises neutral posture by 15°. If this were also true of sauropods, the true neutral pose of the neck would be much higher than has been depicted. An additional 11% of zygapophyseal facet length translates to 11% more range of motion at each joint. More precise quantitative results must await detailed modelling. In summary, including cartilage in our models of sauropod necks shows that they were longer, more elevated and more flexible than previously recognised.

Hemilaminectomy and vertebral stabilization for thoracolumbar intervertebral disc associated dynamic compression in 11 dogs

OBJECTIVE

To describe the diagnostic findings, surgical technique and outcome in dogs with thoracolumbar intervertebral disc-associated dynamic compression.

STUDY DESIGN

Retrospective case series.

ANIMALS

Client owned dogs (n = 11).

METHODS

Medical records (2005-2010) of dogs with a stress myelographic diagnosis of spinal cord injury due to thoracolumbar intervertebral disc-associated dynamic compression with inconclusive compression in the neutral myelographic views that had hemilaminectomy and vertebral stabilization were reviewed. Data on pre- and postoperative neurologic status, diagnostic findings, surgical techniques and outcomes were retrieved. Follow-up clinical and radiographic evaluations were performed immediately, and at approximately one, two, and six months postoperatively as well as at annual follow-up examinations.

RESULTS

The stress myelography demonstrated distinct ventral dynamic compression due to bulging of the disc and additional dorsal compression due to infolding of the ligamentum flavum in some cases. The median percentage of post-stress reduction in spinal cord height on the lateral view was 18.0% (9.8-27.2%). All dogs recovered after surgery and at follow-up examinations were still ambulatory (median: 45 months, range: 7 to 94 months).

CONCLUSIONS AND CLINICAL RELEVANCE

Thoracolumbar intervertebral disc degeneration may result in disc-associated dynamic compression. Stress myelography was an effective means of diagnosing this condition and hemilaminectomy with vertebral stabilization was an effective treatment resulting in long-term neurological improvement in all dogs.

Agreement between magnetic resonance imaging, myelography, and surgery for detecting recurrent, thoracolumbar intervertebral disc extrusion in dogs

OBJECTIVES

Although magnetic resonance imaging (MRI) is reported to be superior to myelography to determine the location and site of first time disc herniation, comparison of these diagnostic methods in cases of recurrent intervertebral disc disease (IVD) herniation after a first surgery has not been evaluated. The objective was to compare the diagnostic accuracy of MRI and myelography in a series of dogs undergoing repeat surgical decompression for recurrent IVD extrusion when compared to the gold standard of surgery.

METHODS

Ten dogs with recurrent IVD herniation underwent MRI and myelography followed by surgical decompression. Three observers reviewed the images to determine the site and side of the first surgery and the recurrent lesion. Agreement was determined by calculating a kappa (κ) score.

RESULTS

Substantial interobserver agreement was noted for recurrent lesion site using MRI and myelography (κ = 0.77 vs. 0.73) and when comparing MRI and myelography to the reported surgical site (κ = 0.73 vs. 0.67). Interobserver agreement was greater with MRI for circumferential location compared to myelography (κ = 0.76 vs. 0.43), similar to what was found when comparing to surgical side (κ = 0.82 vs. 0.49). The previous surgical site in this study had no effect on ability to identify the new lesion.

CLINICAL SIGNIFICANCE

Despite the limitations of MRI, there was greater agreement between observers using MRI for both the recurrent and first lesion.

Advanced imaging: use and misuse

SUMMARY

The primary purpose of diagnostic imaging is to enable clinicians to make correct decisions about a patient's diagnosis and severity of its condition and, thereby, to contribute to effective and efficient treatment. Advanced imaging modalities are inherently better detectors of morphological lesions than radiography; hence, they offer the possibility of more accurate diagnosis and staging, with correspondingly better patient outcomes. However, there is a lack of evidence that better outcomes are being realised for veterinary patients. Furthermore, increased use of advanced imaging carries the possibility of increased misuse, primarily through unnecessary studies that contribute little to patient management other than increased costs.

SCOPE

This article is intended to be relevant to all veterinary species. Advanced imaging of cats is not sufficiently developed as a specific discipline that a balanced review could be based purely on feline examples or references.

Computed tomography myelographic findings in dogs with cervical spondylomyelopathy

Computed tomography (CT) myelography is used occasionally in the diagnosis of cervical spondylomyelopathy, but the type of lesion found in large- versus giant-breed dogs using this modality has not been characterized. Our purpose was to report the frequency of compressive lesions in large- and giant-breed dogs with cervical spondylomyelopathy and imaged using CT myelography. Fifty-eight dogs were retrospectively studied, 23 large-breed and 35 giant-breed dogs. Multiple sites of compression were found in 12 large-breed dogs (52.2%) compared to 30 (85.8%) giant-breed dogs. The main site of compression was at C5-6 and C6-7 in both large-breed (91.3%) and giant-breed (72.4%) dogs. The main cause and direction of compression was disc-associated and ventral in 19 (82.6%) of the large-breed dogs while osseous changes were the primary cause of compression in 27 (77.2%) of the giant-breed dogs, with most compressions being lateral (51.4%), followed by dorsolateral (14.2%). Osseous compression was observed at C7-T1 in eight giant-breed dogs (22.8%), and at T1-T2 or T2 only in five dogs (14.3%). Four of 23 large-breed dogs (17.4%), and seven (20%) of 35 giant-breed dogs had spinal cord atrophy. Therefore, giant-breed dogs often have multiple compressions, usually caused by osseous changes causing lateralized compressions. In large-breed dogs most compressions are disc-associated and located ventrally. Considering the number of giant-breed dogs with compressions at C7-T1, T1-2, and T2, it is important to include the cranial thoracic region when imaging dogs suspected of having cervical spondylomyelopathy.

MRI features of cervical articular process degenerative joint disease in Great Dane dogs with cervical spondylomyelopathy

Cervical spondylomyelopathy or Wobbler syndrome commonly affects the cervical vertebral column of Great Dane dogs. Degenerative changes affecting the articular process joints are a frequent finding in these patients; however, the correlation between these changes and other features of cervical spondylomyelopathy are uncertain. We described and graded the degenerative changes evident in the cervical articular process joints from 13 Great Danes dogs with cervical spondylomyelopathy using MR imaging, and evaluated the relationship between individual features of cervical articular process joint degeneration and the presence of spinal cord compression, vertebral foraminal stenosis, intramedullary spinal cord changes, and intervertebral disc degenerative changes. Degenerative changes affecting the articular process joints were common, with only 13 of 94 (14%) having no degenerative changes. The most severe changes were evident between C4-C5 and C7-T1 intervertebral spaces. Reduction or loss of the hyperintense synovial fluid signal on T2-weighted MR images was the most frequent feature associated with articular process joint degenerative changes. Degenerative changes of the articular process joints affecting the synovial fluid or articular surface, or causing lateral hypertrophic tissue, were positively correlated with lateral spinal cord compression and vertebral foraminal stenosis. Dorsal hypertrophic tissue was positively correlated with dorsal spinal cord compression. Disc-associated spinal cord compression was recognized less frequently.

Imaging dogs with suspected disc herniation: pros and cons of myelography, computed tomography, and magnetic resonance

Myelography, computed tomography (CT), and magnetic resonance (MR) imaging are the diagnostic modalities currently used in the evaluation of dogs with suspected disc herniation. Where high-field MR imaging is available, it is considered the optimal modality for any myelopathy in dogs, including those with disc disease. CT myelography may be the next best option, particularly in nonchondrodystrophoid dogs. In chondrodystrophoid dogs, in which extrusion of mineralized disc material is common, plain CT will enable diagnosis in most cases. Myelography is still considered adequate for diagnosis of disc herniation when MR and CT are unavailable.

Incidence of and risk factors for seizures after myelography performed with iohexol in dogs: 503 cases (2002-2004)

OBJECTIVE

To establish the incidence of and risk factors for seizures following myelography performed with iohexol in dogs.

DESIGN

Retrospective case series.

ANIMALS

503 dogs.

PROCEDURES

Medical records were searched for dogs that underwent myelography between April 2002 and December 2004. Data extracted included body weight, breed, age, sex, volume and dose of iohexol, site of injections, location of lesion, duration of anesthesia, surgical procedures immediately after myelography, use of acepromazine, and presence or absence of seizures.

RESULTS

15 (3%) dogs had postmyelographic seizures. Risk factors significantly associated with seizures were size of dogs (large dogs were 35.35 times as likely to have seizures as were small dogs), location of contrast medium injection (dogs in which iohexol was injected into the cerebellomedullary cistern were 7.4 times as likely to have seizures as were dogs in which iohexol was injected into the lumbar cistern), location of lesion (dogs with lesions at the level of the cervical portion of the vertebral column were 4.65 times as likely to develop seizures as were dogs with lesions in other regions), and total volume of iohexol. Mean ± SD total volume of iohexol was 11.73 ± 5.52 mL (median, 10.5 mL [range, 3.0 to 21.0 mL]) for dogs that had seizures and 4.57 ± 4.13 mL (median, 3.5 mL [range, 0.75 to 45.0 mL]) for those that did not.

CONCLUSIONS AND CLINICAL RELEVANCE

Large-breed dogs with cervical lesions and large volumes of iohexol injected into the cerebellomedullary cistern had the highest risk of seizures. The use of contrast medium volumes > 8 mL in large dogs should be avoided, with preference given to injections into the lumbar cistern.

Surgical treatment of disk-associated wobbler syndrome by a distractable vertebral titanium cage in seven dogs

OBJECTIVE

To evaluate a distractable titanium cage for the treatment of disk-associated wobbler syndrome (DAWS).

STUDY DESIGN

Prospective study.

ANIMALS

Dogs (n = 7) with DAWS.

METHODS

After total discectomy of C5-C6 and C6-C7, the median part of the vertebral body of C6 was removed with preservation of the lateral walls and dorsal cortex. The removed cancellous bone was collected. The implant was placed in the bony defect of C6. After placement, the titanium cage was distracted and affixed by 4 screws. Finally, the implant was filled and covered with cancellous bone. Dogs had follow-up examinations at 1, 3, 6, 12, and 24 months. Six months after surgery, cervical radiographs and computed tomography (CT) were performed.

RESULTS

Although no intraoperative complications occurred, correct placement of the cage was technically challenging. Revision surgery was necessary in 2 dogs because of implant loosening and aggravation of vertebral tilting. All dogs improved after discharge from the hospital. In 1 dog, recurrence of clinical signs caused by articular facet proliferation at an adjacent intervertebral disk space occurred. Radiographs at 6 months demonstrated cage subsidence in 4 dogs. In all dogs, CT was suggestive for fusion of the bone graft with the vertebral body.

CONCLUSIONS

Although results are promising, technical adaptations will be necessary to make this specific surgical technique, designed for humans, suitable for routine use in dogs.

Transcranial magnetic stimulation in Doberman Pinschers with clinically relevant and clinically irrelevant spinal cord compression on magnetic resonance imaging

OBJECTIVE

To evaluate the use of transcranial magnetic stimulation for differentiating between clinically relevant and clinically irrelevant cervical spinal cord compression on magnetic resonance imaging (MRI).

DESIGN

Validation study.

ANIMALS

Clinically normal Doberman Pinschers without (n = 11) and with (6) spinal cord compression on MRI and 16 Doberman Pinschers with disk-associated wobbler syndrome (DAWS).

PROCEDURES

After dogs were sedated, transcranial magnetic motor evoked potentials were recorded from the extensor carpi radialis muscle (ECRM) and cranial tibial muscle (CTM). Onset latencies and peak-to-peak amplitudes were measured. Magnetic resonance imaging was performed to identify spinal cord compression.

RESULTS

There were significant differences in ECRM and CTM onset latencies between Doberman Pinschers with DAWS and each of the 2 groups of clinically normal dogs, but there were no significant differences in ECRM and CTM onset latencies between the 2 groups of clinically normal dogs. There were significant differences in CTM peak-to-peak amplitudes between Doberman Pinschers with DAWS and each of the 2 groups of clinically normal dogs, but there were no significant differences in ECRM peak-to-peak amplitudes among groups or in CTM peak-to-peak amplitudes between the 2 groups of clinically normal dogs. There was a significant correlation between severity of spinal cord compression and ECRM onset latency, CTM onset latency, and CTM peak-to-peak amplitude.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that transcranial magnetic stimulation may be a useful diagnostic tool to differentiate between clinically relevant and clinically irrelevant spinal cord compression identified on MRI alone.

Morphometric dimensions of the caudal cervical vertebral column in clinically normal Doberman Pinschers, English Foxhounds and Doberman Pinschers with clinical signs of disk-associated cervical spondylomyelopathy

Client-owned, clinically normal Doberman Pinschers (n=20), English Foxhounds (n=17), and Doberman Pinschers with clinical signs of disk-associated cervical spondylomyelopathy (DA-CSM) (n=17) were prospectively studied. All dogs underwent magnetic resonance imaging (MRI) of the cervical vertebral column. To evaluate vertebral canal stenosis, the canal occupying ratios of the spinal cord and cerebrospinal fluid (CSF)-column were calculated from C5 to C7. To evaluate the degree of spinal cord compression and the amount of canal compromise, the compression ratio, remaining spinal cord and CSF-column area, and vertebral canal and dorsoventral vertebral canal compromise ratios were calculated at the site of most severe compression. For each canal occupying ratio, there was a significant higher value (implicating less space available for the spinal cord in the vertebral canal) at the level of C7 for clinically affected Doberman Pinschers compared with clinically normal English Foxhounds. The remaining spinal cord area was significantly smaller in dogs with clinically relevant spinal cord compression compared to dogs with clinically irrelevant spinal cord compression. Relative stenosis of the caudal cervical vertebral canal occurred more often in Doberman Pinschers with DA-CSM compared to English Foxhounds and a critical degree of spinal cord compression should be reached to result in clinical signs.

Doença do disco intervertebral cervical em cães: 28 casos (2003-2008)

O objetivo deste estudo foi identificar cães com doença do disco intervertebral (DDIV) cervical atendidos no Hospital Veterinário Universitário (HVU) da Universidade Federal de Santa Maria (UFSM) entre janeiro de 2003 e outubro de 2008 e obter informações a respeito de raça, sexo, idade, sinais neurológicos, resposta ao tratamento cirúrgico, complicações, tempo de recuperação funcional após a cirurgia e ocorrência de recidiva. Hiperestesia cervical foi observada em todos os cães (n=28). Quanto ao grau de disfunção neurológica foram verificados: grau I (8/28[28,5%]), grau II (3/28 [10,7%]), grau III (5/28[17,8%]) e grau V (12/2 [42,8%]). A duração dos sinais neurológicos antes da cirurgia em sete cães (25%) permaneceu por até 15 dias, em 14 cães (50%) entre 15 e 30 dias e nos outros sete cães (25%) por mais de 30 dias. A recuperação satisfatória e sem recidiva foi observada em todos os cães submetidos ao tratamento cirúrgico e que sobreviveram (n=21). Pode-se concluir que a DDIV cervical em nossa rotina acomete principalmente cães adultos, machos, de raças condrodistróficas e não condrodistróficas, incluindo as de grande porte; a hiperestesia cervical é a principal manifestação clínica; a técnica de fenda ventral promove recuperação funcional satisfatória e sem recidiva; as principais complicações trans-operatórias são a hemorragia do plexo venoso, a bradicardia e a hipotensão; e a duração dos sinais clínicos não interfere no tempo de recuperação pós-operatória dos cães.

Does choice of imaging modality affect outcome in dogs with thoracolumbar spinal conditions?

OBJECTIVES

A retrospective cross-sectional study was done to look for differences in outcome in canine spinal patients that had myelography compared to those that had magnetic resonance imaging.

METHODS

Medical records of dogs with spinal conditions in the period January 2004 to December 2007 were reviewed. Data on patient age, gender, breed, size, neurolocalisation, rate of onset, imaging modality, time taken to image, type of treatment, neurological grade at admission and discharge, length and cost of hospitalisation and status at discharge were collected. Only dogs with neurological grade 3 to 6 with signs referable to the thoracolumbar spine were included.

RESULTS

Of 107 dogs that met the inclusion criteria, 66 (62%) had myelography and 41 (38%) had magnetic resonance imaging. Using multivariable analyses, non-chondrodystrophoid breed, increasing age and higher neurological grade at admission were found to be associated negatively with survival. Neurological grade 5 at admission was found to be associated positively with likelihood of neurological improvement. Male gender, higher neurological grade at admission and medical treatment were associated negatively with length of hospitalisation. magnetic resonance imaging, surgical treatment and period of hospitalisation were associated positively with total cost of hospitalisation.

CLINICAL SIGNIFICANCE

No significant association was found between type of imaging and any patient outcome variables except cost of hospitalisation, which was higher for dogs having magnetic resonance imaging. Although magnetic resonance imaging may be considered advantageous compared to myelography because it is non-invasive and provides superior anatomical detail for surgical guidance, no beneficial effect on outcome of dogs with non-ambulatory thoracolumbar spinal disease was found.

Outcome of medical and surgical treatment in dogs with cervical spondylomyelopathy: 104 cases (1988-2004)

OBJECTIVE

To compare outcomes and survival times for dogs with cervical spondylomyelopathy (CSM; wobbler syndrome) treated medically or surgically.

DESIGN

Retrospective case series.

ANIMALS

104 dogs.

PROCEDURES

Medical records of dogs were included if the diagnosis of CSM had been made on the basis of results of diagnostic imaging and follow-up information (minimum, 6 months) was available. Ordinal logistic regression was used to compare outcomes and the product-limit method was used to compare survival times between dogs treated surgically and dogs treated medically.

RESULTS

37 dogs were treated surgically, and 67 were treated medically. Owners reported that 30 (81%) dogs treated surgically were improved, 1 (3%) was unchanged, and 6 (16%) were worse and that 36 (54%) dogs treated medically were improved, 18 (27%) were unchanged, and 13 (19%) were worse. Outcome was not significantly different between groups. Information on survival time was available for 33 dogs treated surgically and 43 dogs treated medically. Forty of the 76 (53%) dogs were euthanized because of CSM. Median and mean survival times were 36 and 48 months, respectively, for dogs treated medically and 36 and 46.5 months, respectively, for dogs treated surgically. Survival times did not differ significantly between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

In the present study, neither outcome nor survival time was significantly different between dogs with CSM treated medically and dogs treated surgically, suggesting that medical treatment is a viable and valuable option for management of dogs with CSM.

Pseudolayering artefact on postcontrast magnetic resonance images of the bladder of 18 dogs and three cats

An artefact was observed on postcontrast magnetic resonance imaging (mri) of the urinary bladder of several small animals; it took the form of a dark layer in the dependent (dorsal) part of the bladder, with a thin hyperintense layer on top of it, and a hypointense signal in the rest of the non-dependent (ventral) part. The mri database was searched for animals with T1-weighted images of the urinary bladder after the injection of gadolinium. Eighteen dogs and three cats were included in the study. The artefact was observed in 16 of the animals on the postcontrast images but not on the T1-weighted and T2-weighted precontrast images. A phantom experiment showed that the signal intensity observed on T1-weighted images decreased rapidly as the concentration of gadolinium increased from 6.25 mmol/l to 25 mmol/l. It is hypothesised that the early excretion of concentrated gadolinium into the bladder causes the pseudolayering artefact observed, which has also been reported in human patients.