Dorsal laminectomy for caudal cervical spondylomyelopathy: postoperative recovery and long-term follow-up in 20 dogs

OBJECTIVE: To evaluate the postoperative morbidity and long-term outcome of dogs after dorsal laminectomy for caudal cervical spondylomyelopathy (CCSM). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Twenty dogs with CCSM. METHODS: Medical records of dogs treated by dorsal laminectomy for CCSM at North Carolina State University and Colorado State University between 1989 and 1999 were reviewed. Information on signalment, onset, progression and duration of clinical signs, diagnostic testing, sites of dorsal laminectomy, postoperative complications, length of hospitalization, and the ambulatory status on discharge was recorded. A minimum follow-up of 7 months was required for inclusion in the study. Neurologic status was graded (0 to 5) preoperatively, 2 days after surgery, and at the time of the study (final score). Improvement or worsening of the neurologic status was assessed by comparison of different scores for each dog. Additional follow-up information was obtained by means of a detailed telephone questionnaire directed at both the owner and referring veterinarian. RESULTS: Mean duration of clinical signs before surgery was 4.9 months. At admission, 15 dogs were ambulatory and 5 were nonambulatory. Neurologic status worsened in 70% of dogs 2 days after surgery but improved in all but 1 dog over the long term. Mean time to optimal recovery was 3.6 months. Long-term follow-up ranged from 7 months to 9 years (mean +/- SD, 3.2 +/- 2.4 years). Four dogs had confirmed recurrence; 2 other dogs may have had recurrence. CONCLUSIONS: Dorsal cervical laminectomy is an effective treatment for CCSM in those dogs with dorsal compression or multiple sites of involvement. CLINICAL RELEVANCE: Although most dogs' neurologic status transiently worsened after surgery, long-term outcome and recurrence rates were comparable to those seen with other surgical techniques for CCSM.     

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.     

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.     

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.     

Comparison of two surgical techniques for the management of cervical spondylomyelopathy in dobermanns

A study was undertaken to compare the efficacy of two surgical techniques for the treatment of caudal cervical spondylomyelopathy (CCSM): ventral decompression (slot) and vertebral distraction and stabilisation with a screw and washer (screw/washer). Twenty-eight dobermanns managed surgically for disc-associated CCSM during a four-year period were studied retrospectively. The maximum postoperative period was 40 months. Cases were excluded if a minimum follow-up of 24 months after surgery could not be made. A 'slot' took a longer time to perform and had a higher rate of immediate postoperative deterioration. Duration of hospital stay was similar for both procedures. At six months after surgery the two techniques were comparable; 12/14 (screw/washer) and 13/14 (slot) patients were deemed to have a satisfactory outcome. Recurrence of cervical spinal cord disease was higher in the screw/washer dogs. At one year after surgery the recurrence rate was zero (slot) and 5/14 (screw/washer), respectively. At two years after surgery 4/14 of the slot dogs had deteriorated compared to 7/14 of the screw/washer dogs. Where Investigated, the cause of deterioration was either a domino disc lesion or vertebral endplate collapse and dorsal displacement of the screw and washer.     

Vertical patellar position in large-breed dogs with clinically normal stifles and large-breed dogs with medial patellar luxation

OBJECTIVE: To further define vertical patellar position, as measured by the ratio of patellar ligament length to patellar length (L:P), in large-breed dogs with clinically normal stifles and compare that to the L:P of large-breed dogs with medial patellar luxation (MPL). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Large-breed dogs (n = 50) with clinically normal stifle joints and 30 large-breed dogs with MPL. METHODS: Large-breed dogs with clinically normal stifle joints or MPL were identified and divided into groups (NORM and MPL, respectively). L:P values were determined for each dog by 4 observers from single lateral stifle radiographs. L:P was compared between NORM and MPL groups and 95% confidence intervals (CIs) were calculated. RESULTS: All 4 observers found a significantly higher L:P (more proximally positioned patella) for the MPL group compared with the NORM group. Overall mean (+/-SEM) L:P were: NORM, 1.71+/-0.020 and MPL, 1.87+/-0.025. The 95% CI was determined to be 1.45-1.97 for the NORM group and 1.57-2.17 for the MPL group. CONCLUSIONS: Large-breed dogs with MPL had a significantly more proximal vertical patellar position compared with large-breed dogs with clinically normal stifles. Large-breed dogs with L:P values >1.97 are considered to have patella alta. CLINICAL RELEVANCE: Proximal displacement of the patella within the femoral trochlear groove may play a role in MPL in large-breed dogs.     

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.     

Correlation between severity of clinical signs and motor evoked potentials after transcranial magnetic stimulation in large-breed dogs with cervical spinal cord disease

OBJECTIVE: To evaluate use of transcranial magnetic motor evoked potentials for assessment of the functional integrity of the cervical spinal cord in large-breed dogs with cervical spinal cord disease. DESIGN: Randomized, controlled, masked study. ANIMALS: 10 healthy large-breed control dogs and 25 large-breed dogs with cervical spinal cord diseases. PROCEDURE: Affected dogs were allocated to 3 groups on the basis of neurologic status: signs of neck pain alone, ambulatory with ataxia in all limbs, or nonambulatory. Transcranial magnetic stimulation was performed on each dog with the same standard technique. Motor evoked potentials (MEP) were recorded from electrodes inserted in the tibialis cranialis muscle. Following the procedure, each dog was anesthetized and cervical radiography, CSF analysis, and cervical myelography were performed. The MEP latencies and amplitudes were correlated with neurologic status of the dogs after correction for neuronal path length. RESULTS: Mean MEP latencies and amplitudes were significantly different between control dogs and dogs in each of the 3 neurologic categories, but were not significantly different among dogs in the 3 neurologic categories. A linear association was evident between MEP latencies and amplitudes and severity of neurologic deficits; the more severe the neurologic deficits, the more prolonged the latencies and the more decreased the amplitudes. CONCLUSIONS AND CLINICAL RELEVANCE: Transcranial magnetic MEP are useful to assess severity of cervical spinal cord disease in large-breed dogs. Impairment of the functional integrity of the cervical spinal cord was found even in dogs with neck pain alone.     

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.     

Retrospective analysis of axial skeleton osteosarcoma in 22 large-breed dogs

Medical-records of 22 large-breed dogs (>15 kg) with osteosarcoma (OSA) of the axial skeleton were reviewed to determine prevalence of metastasis and survival associated with this neoplasm. All dogs were treated with more than 1 mode of therapy including palliative radiation (n = 12), definitive radiation (n = 8), surgery (n = 7), chemotherapy (n = 12), or some combination of these therapies. Metastasis was documented in 10 of 22 dogs (46%), and the median survival for all dogs was 137 days. Primary cause of death was local tumor recurrence (54%). Breed (retriever versus purebred versus mixed-breed survival was 100, 182, and 264 days, respectively) and radiation therapy protocol (survival in dogs treated with palliative radiation therapy versus those treated with definitive radiation therapy was 79 and 265 days, respectively) were significantly related to survival (P < .05). Prevalence of metastasis and median survival for large-breed dogs with axial skeleton OSA seems to be similar to that reported for large-breed dogs with appendicular skeleton OSA. Definitive radiation therapy may have a role in the treatment of axial skeleton osteosarcoma.