Distracted cervical spinal fusion for management of caudal cervical spondylomyelopathy in large-breed dogs

Using an autogenous bone graft (obtained from the iliac crest), 4-mm cancellous bone screws, and polymethylmethacrylate, a distracted cervical spinal fusion technique was performed on 10 dogs with myelographic evidence of caudal cervical spondylomyelopathy. All dogs had evidence of dynamic soft tissue spinal cord compression, as indicated by flexion, extension, and traction myelographic views. Of the 10 dogs, 4 previously had undergone surgery by use of ventral slot or cervical disk fenestration techniques, and their neurologic status had deteriorated after the original surgery. Preoperative neurologic status of the 10 dogs included nonambulatory tetraparesis (n = 5), severe ataxia with conscious proprioceptive deficits (n = 2), and mild ambulatory ataxia with conscious proprioceptive deficits (n = 3). Five dogs had signs of various degrees of cervical pain. Clinical improvement was observed in 8 of 10 dogs--either improved neurologic status or elimination of cervical pain. Implant loosening developed in 3 dogs; 2 of them were euthanatized because of lack of neurologic improvement. Radiographic evidence of bony cervical fusion was observed during a 9- to 24-week period in 6 of the 8 surviving dogs. The distracted cervical fusion technique appears to be a valid surgical procedure to manage cervical spondylomyelopathy in those dogs in which the lesions are limited to one cervical intervertebral disk space.     

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.     

Intervertebral and intravertebral ratios in Doberman pinscher dogs with cervical spondylomyelopathy

No screening method is currently available to differentiate dogs with and without cervical spondylomyelopathy. Intravertebral and intervertebral ratios are used in horses and can predict cervical vertebral malformation. Intervertebral ratios could be a useful screening method for canine cervical spondylomyelopathy. Our purpose was to compare cervical intervertebral and intravertebral ratios in normal vs. affected Doberman pinschers. Forty dogs were studied, 27 affected and 13 normal. Cervical radiographs were obtained in all dogs. The minimum intra- and intervertebral sagittal diameter ratios were established for each cervical vertebrae and disc space from C(2) to C(7) . Comparisons were made between groups and specific vertebral body and disc levels. The effect of gender, age, and method of measurement (analog or digital radiographs) was also studied. There was no difference in either the intervertebral or intravertebral ratio between normal vs. affected dogs. The ratios decreased progressively along the cervical spine, being smallest at C(6) -C(7) and C(7) , respectively. Age, gender, and method of measurement had a significant influence on both inter- and intravertebral ratios, with smaller ratios seen as dogs aged and in male dogs. Based on our results, inter- or intravertebral ratios have no value to distinguish between clinically normal Doberman pinschers and Doberman pinschers with cervical spondylomyelopathy.     

Bicortical implant insertion in caudal cervical spondylomyelopathy: a computed tomography simulation in affected Doberman Pinschers

Objective— To evaluate the safety of the angle of insertion of bicortical implants in Doberman Pinschers affected by caudal cervical spondylomyelopathy (CCSM) using simulation on computed tomography (CT) images.
Animals— Doberman Pinschers (n=9) with dynamic spinal compression attributed to CCSM.
Methods— Dogs had CT evaluation of the cervical vertebral column. Digital images were used to evaluate the safety of bicortical implant insertion from the midline at 30, 35, and 40° inclination by drawing a line simulating implant position. Correct surgical positioning of dogs was evaluated by measuring the degree of rotation of the spine along the longitudinal axis.
Results— Insertion of an implant at 30, 35, and 40° inclination was considered safe in 42%, 59%, and 67% of selected sites. Rotation of the spine from 9° counter clockwise to 10° clockwise along the longitudinal axis occurred in 53% of the areas considered.
Conclusions— These results suggest that bicortical implants in the caudal cervical area in Doberman Pinschers affected by CCSM carry a high risk of vertebral canal and intervertebral foramina violation.
Clinical Relevance— Bicortical implants inserted at 30 and 35° in the caudal cervical area in Doberman Pinschers affected by CCSM carry a high risk of vertebral canal and intervertebral foramina violation. CT planning for individual dogs can facilitate selection of the appropriate insertion plane and vertebral column rotation needs to be considered in surgical planning.     

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.     

Intraoperative use of ultrasonography during continuous dorsal laminectomy in two dogs with caudal cervical vertebral instability and malformation ("Wobbler syndrome")

OBJECTIVE: To describe an intraoperative ultrasound imaging technique during dorsal laminectomy in 2 dogs with caudal cervical vertebral instability and malformation (CCVIM, "Wobbler syndrome"). STUDY DESIGN: Clinical case report. SAMPLE POPULATION: Two dogs with CCVIM. RESULTS: On neurologic examination there was tetraparesis with upper motor neuron signs in the thoracic limbs and lower motor neuron signs in the pelvic limbs in dog 1, and hyperreflexia of the rear limbs, normoreflexia of the right front limb, and hyporeflexia of the left front limb of dog 2. Both dogs had signs of marked cervical pain and radiographic signs of cervical spinal cord compression. Intraoperative ultrasonography of the spinal cord revealed protruding intervertebral disc at C5-6 (dog 1) and C6-7 (dog 2), and the parallel borders of the spinal cord and central canal after decompression. Continuous dorsal laminectomy (CDL) resulted in improvement over 16 months (dog 1) and 20 months (dog 2). CONCLUSIONS: Intraoperative ultrasonographic imaging of the cervical spinal cord after CDL was helpful in determining adequate decompression (postlaminectomy) of the spinal cord in relation to the ventral and lateral compressive component(s) and to image the protruding intervertebral disc. CLINICAL RELEVANCE: Intraoperative ultrasonography can be used to provide valuable information on the spinal cord and surrounding soft tissues for the neurosurgeon.     

Disc extrusion in a Rottweiler dog with caudal cervical spondylomyelopathy after failure of intervertebral distraction/stabilisation

A Rottweiler dog was presented with an 8 week history of hindlimb ataxia. Neurological examination localised the lesion to the cervical spinal cord. Myelography demonstrated dynamic compressive lesions at C5-6 and C6-7 consistent with a diagnosis of caudal cervical spondylomyelopathy. Distraction/stabilisation of both discs was performed using interbody polymethyl methacrylate. Both implants subsequently failed leading to extrusion of the remaining dorsal annulus fibrosus of the C5-6 intervertebral disc and nonambulatory tetraparesis. A ventral slot combined with distraction/stabilisation using screws and polymethyl methacrylate was performed and resulted in nearly full neurological recovery.     

Evaluation of osseous‐associated cervical spondylomyelopathy in dogs using kinematic magnetic resonance imaging

Osseous‐associated cervical spondylomyelopathy in dogs is characterized by both static and dynamic spinal cord compression; however, standard MRI methods only assess static compression. In humans with cervical spondylotic myelopathy, kinematic MRI is commonly used to diagnose dynamic spinal cord compressions. The purpose of this prospective, analytical study was to evaluate kinematic MRI as a method for characterizing the dynamic component of osseous‐associated cervical spondylomyelopathy in dogs. We hypothesized that kinematic MRI would allow visualization of spinal cord compressions that were not identified with standard imaging. Twelve client‐owned dogs with osseous‐associated cervical spondylomyelopathy were enrolled. After standard MRI confirmed a diagnosis of osseous‐associated cervical spondylomyelopathy, a positioning device was used to perform additional MRI sequences with the cervical vertebral column flexed and extended. Morphologic and morphometric (spinal cord height, intervertebral disc width, spinal cord width, vertebral canal height, and spinal cord area) assessments were recorded for images acquired with neutral, flexion, and extension imaging. A total of 25 compressions were seen with neutral positioning, while extension identified 32 compressions. There was a significant association between extension positioning and presence of a compressive lesion at C4‐C5 (p = 0.02). Extension was also associated with a change in the most severe site of compression in four out of 12 (33%) dogs. None of the patients deteriorated neurologically after kinematic imaging. We concluded that kinematic MRI is a feasible method for evaluating dogs with osseous‐associated cervical spondylomyelopathy, and can reveal new compressions not seen with neutral positioning.     

Clinical and magnetic resonance imaging (MRI) findings in 26 dogs with canine osseous-associated cervical spondylomyelopathy

The potential link between degenerative changes seen on magnetic resonance imaging (MRI) in osseous-associated cervical spondylomyelopathy (OA-CSM) and clinical signs has not been explored. Our goal was to retrospectively evaluate MRI findings, while investigating potential correlations between these changes, signalment, and clinical signs. Twenty-six dogs diagnosed with OA-CSM were included in the study. Clinical signs were converted into a Modified Frankel Score (MFS) and MRI findings were assessed and graded. Giant breeds had multiple compressed sites and presented at a younger age than large breeds, suggesting a different underlying pathophysiology. Spinal cord compression, most commonly bilateral, was present in 36.8% of intervertebral spaces. Synovial fluid loss and articular process sclerosis were the most common degenerative changes. Most dogs showed identical MFS scores, and no significant correlations were found between MFS and MRI changes. More detailed functional scales should be used to investigate this in the future.