Association between various physical factors and acute thoracolumbar intervertebral disk extrusion or protrusion in Dachshunds

OBJECTIVE: To determine whether body weight, body condition score, or various body dimensions were associated with acute thoracolumbar intervertebral disk extrusion or protrusion and whether any of these factors were associated with severity of clinical signs in Dachshunds. DESIGN: Cross-sectional clinical study. ANIMALS:75 Dachshunds with (n = 39) or without (36) acute thoracolumbar intervertebral disk extrusion or protrusion. PROCEDURES: Signalment, various body measurements, body weight, body condition score, and spinal cord injury grade were recorded at the time of initial examination. RESULTS: Mean T1-S1 distance and median tuber calcaneus-to-patellar tendon (TC-PT) distance were significantly shorter in affected than in unaffected dogs. A 1-cm decrease in T1-S1 distance was associated with a 2.1-times greater odds of being affected, and a 1-cm decrease in TC-PT distance was associated with an 11.1-times greater odds of being affected. Results of multivariable logistic regression also indicated that affected dogs were taller at the withers and had a larger pelvic circumference than unaffected dogs, after adjusting for other body measurements. Results of ordinal logistic regression indicated that longer T1-S1 distance, taller height at the withers, and smaller pelvic circumference were associated with more severe spinal cord injury. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that certain body dimensions may be associated with acute thoracolumbar intervertebral disk extrusion or protrusion in Dachshunds and, in affected dogs, with severity of neurologic dysfunction.     

Prognostic value of magnetic resonance imaging in dogs with paraplegia caused by thoracolumbar intervertebral disk extrusion: 77 cases (2000-2003)

OBJECTIVE: To determine whether magnetic resonance imaging findings in dogs with paraplegia caused by thoracolumbar intervertebral disk extrusion were predictive of clinical outcome. DESIGN: Retrospective case series. ANIMALS: 77 dogs. PROCEDURE: Medical records and magnetic resonance images were reviewed; clinical outcome was classified as successful (regained ability to walk with no more than mild neurologic deficits) or unsuccessful (severe neurologic deficits persisted). The prognostic value of magnetic resonance imaging was compared with prognostic value of deep pain perception, duration of clinical signs, and rate of onset of clinical signs. RESULT: 33 (43%) dogs had areas of hyperintensity of the spinal cord greater than or equal to the length of the L2 vertebral body on T2-weighted magnetic resonance images. All 44 dogs without areas of hyperintensity on T2-weighted images had a successful outcome, but only 18 of the 33 (55%) dogs with an area of hyperintensity did. Only 5 of 16 dogs with an area of hyperintensity that had also lost deep pain perception had a successful outcome. The odds ratio for an unsuccessful outcome for a dog with an area of hyperintensity (29.87) was higher than the odds ratio for a dog that had lost deep pain perception (5.24). Duration and rate of onset of clinical signs were not associated with clinical outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggest that results of magnetic resonance imaging can be used to predict clinical outcome in dogs with paraplegia caused by intervertebral disk extrusion.     

Magnetic resonance imaging findings in dogs with thoracolumbar intervertebral disk disease: 69 cases (1997-2005)

OBJECTIVE: To determine magnetic resonance imaging (MRI) abnormalities in dogs with intervertebral disk disease (IVDD) and develop a classification scheme for IVDD in dogs based on MRI findings. DESIGN: Retrospective case series. ANIMALS: 69 dogs. PROCEDURE: Medical records of dogs admitted because of thoracolumbar IVDD in which MRI of T9 through L7 had been performed were reviewed. RESULTS: A total of 759 intervertebral disk spaces were examined. Of these, 342 (45.1%) were classified as having a normal MRI appearance; the remaining 417 (54.9%) had various types of IVDD. Disk degeneration was identified in 276 disk spaces in 56 dogs, bulging of the intervertebral disk was identified in 37 disk spaces in 24 dogs, disk protrusion was identified in 54 disk spaces in 32 dogs, and disk extrusion was identified in 50 disk spaces in 48 dogs. Cartilage endplate changes were identified in 35 vertebrae in 17 dogs, and increased signal intensity of the spinal cord was identified in 21 dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Four types of IVDD (disk degeneration, bulging of the intervertebral disk, disk protrusion, and disk extrusion) were identified on the basis of MRI findings in dogs with thoracolumbar IVDD. We recommend that a standardized nomenclature be adopted for the various types of thoracolumbar IVDD in dogs.     

Comparison of the width of the intervertebral disk space and radiographic changes before and after intervertebral disk fenestration in dogs

Intervertebral disk space widths were measured on lateral radiographs of 73 anesthetized dogs. Weight was found to have a significant (P less than 0.01) effect on disk space width. Using weight-adjusted disk space width measurements for all subsequent studies, older (7- to 16-year-old) dogs and males had consistently, but not significantly, wider, disk spaces than did alternative groups. Cervical and lumbar intervertebral disk spaces tended to be wider than those in the caudal thoracic region. The widest cervical intervertebral disk spaces were C4-5 and C5-6 and the narrowest was C2-3. In the lumbar region, L2-3 was the widest disk space and L4-5 was the narrowest. Dachshunds generally had greater mean intervertebral disk space width than did other breeds of dogs. Cervical (n = 6 dogs) and thoracolumbar (n = 6 dogs) disk fenestration resulted in narrow intervertebral disk spaces, regardless of breed. When a ventral approach was used in thoracolumbar fenestration, the mean intervertebral disk space was narrower than that resulting from use of a dorsolateral approach. Spondylosis was found radiographically 1 to 4 years after intervertebral disk fenestration in 3 of 6 dogs that had cervical fenestrations and in 5 of 6 dogs that underwent thoracolumbar fenestration.     

CLINICAL AND MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF THORACOLUMBAR INTERVERTEBRAL DISK EXTRUSIONS AND PROTRUSIONS IN LARGE BREED DOGS

Treatment recommendations differ for dogs with intervertebral disk extrusion vs. intervertebral disk protrusion. The aim of this retrospective, cross‐sectional study was to determine whether clinical and magnetic resonance imaging (MRI) variables could be used to predict a diagnosis of thoracolumbar intervertebral disk extrusion or protrusion in dogs. Dogs were included if they were large breed dogs, had an MRI study of the thoracolumbar or lumbar vertebral column, had undergone spinal surgery, and had the type of intervertebral disk herniation (intervertebral disk extrusion or protrusion) clearly stated in surgical reports. A veterinary neurologist unaware of surgical findings reviewed MRI studies and recorded number, location, degree of degeneration and morphology of intervertebral disks, presence of nuclear clefts, disk space narrowing, extent, localization and lateralization of herniated disk material, degree of spinal cord compression, intraparenchymal intensity changes, spondylosis deformans, spinal cord swelling, spinal cord atrophy, vertebral endplate changes, and presence of extradural hemorrhage. Ninety‐five dogs were included in the sample. Multivariable statistical models indicated that longer duration of clinical signs (P = 0.01), midline instead of lateralized disk herniation (P = 0.007), and partial instead of complete disk degeneration (P = 0.01) were associated with a diagnosis of intervertebral disk protrusion. The presence of a single intervertebral herniation (P = 0.023) and dispersed intervertebral disk material not confined to the disk space (P = 0.06) made a diagnosis of intervertebral disk extrusion more likely. Findings from this study identified one clinical and four MRI variables that could potentially facilitate differentiating intervertebral disk extrusions from protrusions in dogs.     

Outcome of and complications associated with prophylactic percutaneous laser disk ablation in dogs with thoracolumbar disk disease: 277 cases (1992-2001)

OBJECTIVE: To determine outcome of and complications associated with prophylactic percutaneous laser disk ablation in dogs with thoracolumbar disk disease. DESIGN: Retrospective study. ANIMALS: 277 dogs. PROCEDURE: Medical records of dogs with a history of thoracolumbar disk disease in which the 7 intervertebral disks from T10-11 through L3-4 were ablated with a holmium-yttrium-aluminum-garnet laser inserted through percutaneously placed needles were reviewed. Complications and episodes of a recurrence of neurologic signs (eg, paresis or paralysis) were recorded. Owners were contacted by telephone for follow-up information. RESULTS: Nine of 262 (3.4%) dogs for which follow-up information was available had a recurrence of paresis or paralysis. Follow-up time ranged from 1 to 85 months (mean, 15 months); signs recurred between 3 and 52 months (mean, 15.1 months) after laser disk ablation. Acute complications occurred in 5 dogs and included mild pneumothorax in 1 dog, an abscess at a needle insertion site in 1 dog, and proprioceptive deficits in 3 dogs, 1 of which required hemilaminectomy within 1 week because of progression and severity of neurologic signs. One dog developed diskospondylitis. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that prophylactic percutaneous laser disk ablation is associated with few complications and may reduce the risk of recurrence of signs of intervertebral disk disease in dogs.     

Risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk herniation in dogs: 229 cases (1994-2000)

OBJECTIVE: To assess risk factors for recurrence of clinical signs associated with thoracolumbar intervertebral disk disease (IVDD) in dogs that had decompressive laminectomy without attempted prophylactic treatment of other disk spaces. DESIGN: Retrospective study. ANIMALS: 229 dogs. PROCEDURE: Medical records of dogs that had decompressive laminectomy without prophylactic fenestration for a first episode of IVDD and were available for follow-up were reviewed. Information on 7 clinical and 8 radiographic potential risk factors were recorded. RESULTS: Clinical signs associated with recurrence of IVDD developed in 44 (19.2%) dogs. Ninety-six percent of recurrences developed within 3 years after surgery. Recurrence developed in 25% of Dachshunds and 15% of dogs of other breeds combined. Number of opacified disks was a significant risk factor for recurrence. Risk increased with number of opacified disks in an almost linear manner; each opacified disk increased risk by 1.4 times. Dogs with 5 or 6 opacified disks at the time of first surgery had a recurrence rate of 50%. CONCLUSIONS AND CLINICAL RELEVANCE: When all likely episodes of recurrence are considered and a long follow-up period is achieved, true rate of recurrence of IVDD appears to be higher than in many previous reports. Dogs with multiple opacified disks at the time of first surgery should be considered a high-risk subpopulation.     

Diffusion tensor imaging-based quantitative analysis of the spinal cord in Pembroke Welsh Corgis with degenerative myelopathy

Canine degenerative myelopathy (DM) is a progressive neurodegenerative disease of the spinal cord. The diagnosis is based on the observation of clinical signs, genetic testing, and exclusion of other spinal cord diseases, and a definitive diagnosis of DM can only be confirmed by postmortem histopathological findings. The aim of this study was to investigate the diagnostic ability of diffusion tensor imaging (DTI) for DM. Eight DM-affected Pembroke Welsh Corgis, thirteen dogs with thoracolumbar intervertebral disk herniation (IVDH), and six healthy control dogs were included. All dogs were scanned using a 3.0-T MRI system. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were calculated for each intervertebral disk level slice between T8–T9 and L2–L3 intervertebral disk levels, and the entire area of the thoracolumbar spinal cord between T8–T9 and L2–L3 intervertebral disk levels (T8–L3 region). The ADC and FA values of the T8–L3 region were significantly lower in the DM group than in the IVDH group. The ADC values for the T8–L3 region had a moderate negative correlation with clinical duration (r_s= −0.723, P=0.043); however, the FA values of other intervertebral disk levels and T8–L3 region had no correlation with clinical durations. The measurement of DTI indices can be used to quantitatively assess neurodegeneration and may have diagnostic value for DM. In particular, the ADC value of the T8–L3 region may aid in making a non-invasive premortem diagnosis of DM.     

Association of spinal cord compression seen on magnetic resonance imaging with clinical outcome in 67 dogs with thoracolumbar intervertebral disc extrusion

OBJECTIVES: To determine whether there is an association between the degree of transverse spinal cord compression detected by magnetic resonance imaging following thoracolumbar Hansen type 1 intervertebral disc disease in dogs and their presenting and postsurgical neurological status. METHODS: Medical records of 67 dogs with surgically confirmed Hansen type 1 intervertebral disc disease (2000 to 2004) were reviewed to obtain the rate of onset of disease, duration of clinical signs and presurgical and postsurgical neurological grade. Percentage of spinal cord compression was determined on transverse T2-weighted magnetic resonance images. Linear regression was used to examine the association between spinal cord compression and each of the above variables. Chi-squared tests were used to examine associations among postsurgical outcome and presurgical variables. RESULTS: Eighty-five per cent (57 of 67) of dogs were chondrodystrophoid. Mean spinal cord compression was 53 per cent (sd=219.7, range 14.3 to 84.9 per cent). There was no association between the degree of spinal cord compression and the neurological grade at presentation, rate of onset of disease, duration of clinical signs or postsurgical outcome, with no difference between chondrodystrophoid and non-chondrodystrophoid dogs. CLINICAL SIGNIFICANCE: The degree of spinal cord compression documented with magnetic resonance imaging in dogs with thoracolumbar Hansen type 1 intervertebral disc disease was not associated with the severity of neurological signs and was not a prognostic indicator in this study.     

Quantification of the association between intervertebral disk calcification and disk herniation in Dachshunds

OBJECTIVE: To quantify the association between intervertebral disk calcification and disk herniation in Dachshunds. DESIGN: Longitudinal study. ANIMALS: 61 Dachshunds that had been radiographically screened for calcification of intervertebral disks at 2 years of age in other studies. Thirty-seven of the dogs had survived to the time of the present study and were > or = 8 years of age; 24 others had not survived. PROCEDURES: Radiographic examination of 36 surviving dogs was performed, and information on occurrence of disk calcification at 2 years of age were obtained from records of all 61 Dachshunds. Information on occurrence of disk herniation between 2 and 8 years of age was obtained from owners via questionnaire. Associations between numbers of calcified disks and disk herniation were analyzed via maximum likelihood logistic regression. RESULTS: Disk calcification at 2 years of age was a significant predictor of clinical disk herniation (odds ratio per calcified disk, 1.42; 95% confidence interval, 1.19 to 1.81). Number of calcified disks in the full vertebral column was a better predictor than number of calcified disks between vertebrae T10 and L3. Numbers of calcified disks at > or = 8 years of age and at 2 years of age were significantly correlated. CONCLUSIONS AND CLINICAL RELEVANCE: Number of calcified disks at 2 years of age was a good predictor of clinical disk herniation in Dachshunds. Because of the high heritability of disk calcification, it is possible that an effective reduction in occurrence of severe disk herniation in Dachshunds could be obtained by selective breeding against high numbers of calcified disks at 2 years of age.     

Evaluation of electroacupuncture treatment for thoracolumbar intervertebral disk disease in dogs

OBJECTIVE: To evaluate use of electroacupuncture combined with standard Western medical treatment versus Western medical treatment alone for treatment of thoracolumbar intervertebral disk disease in dogs. DESIGN: Prospective controlled study. ANIMALS: 50 dogs with signs of thoracolumbar intervertebral disk disease. PROCEDURES: Dogs were randomly allocated to 1 of 2 treatment groups and classified as having grade 1 to 5 neurologic dysfunction. Dogs in group 1 received electroacupuncture stimulation combined with standard Western medical treatment; those in group 2 received only standard Western medical treatment. A numeric score for neurologic function was evaluated at 4 time points to evaluate effects of treatments. RESULTS: Time (mean +/- SD) to recover ambulation in dogs with grade 3 and 4 dysfunction in group 1 (10.10 +/- 6.49 days) was significantly lower than in group 2 (20.83 +/- 11.99 days). Success (able to walk without assistance) rate for dogs with grade 3 and 4 dysfunction in group 1 (10/10 dogs) was significantly higher than that of similarly affected dogs in group 2 (6/9 dogs). Dogs without deep pain perception (grade 5 dysfunction) had a success (recovery of pain sensation) rate of 3 of 6 and 1 of 8 in groups 1 and 2, respectively, but the difference was not significant. Overall success rate (all dysfunction grades) for group 1 (23/26; 88.5%) was significantly higher than for group 2 (14/24; 58.3%). CONCLUSIONS AND CLINICAL RELEVANCE: Electroacupuncture combined with standard Western medical treatment was effective and resulted in shorter time to recover ambulation and deep pain perception than did use of Western treatment alone in dogs with signs of thoracolumbar intervertebral disk disease.     

Morphologic and morphometric magnetic resonance imaging features of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy

OBJECTIVE: To compare morphologic and morphometric features of the cervical vertebral column and spinal cord of Doberman Pinschers with and without clinical signs of cervical spondylomyelopathy (CSM; wobbler syndrome) detected via magnetic resonance imaging (MRI). ANIMALS: 16 clinically normal and 16 CSM-affected Doberman Pinschers. PROCEDURES: For each dog, MRI of the cervical vertebral column (in neutral and traction positions) was performed. Morphologically, MRI abnormalities were classified according to a spinal cord compression scale. Foraminal stenosis and intervertebral disk degeneration and protrusion were also recorded. Morphometric measurements of the vertebral canal and spinal cord were obtained in sagittal and transverse MRI planes. RESULTS: 4 of 16 clinically normal and 15 of 16 CSM-affected dogs had spinal cord compression. Twelve clinically normal and all CSM-affected dogs had disk degeneration. Foraminal stenosis was detected in 11 clinically normal and 14 CSM-affected dogs. Vertebral canal and spinal cord areas were consistently smaller in CSM-affected dogs, compared with clinically normal dogs. In neutral and traction positions, the intervertebral disks of CSM-affected dogs were wider than those of clinically normal dogs but the amount of disk distraction was similar between groups. CONCLUSIONS AND CLINICAL RELEVANCE: The incidence of intervertebral disk degeneration and foraminal stenosis in clinically normal Doberman Pinschers was high; cervical spinal cord compression may be present without concurrent clinical signs. A combination of static factors (ie, a relatively stenotic vertebral canal and wider intervertebral disks) distinguished CSM-affected dogs from clinically normal dogs and appears to be a key feature in the pathogenesis of CSM.     

ACCURACY OF MAGNETIC RESONANCE IMAGING FOR ESTIMATING INTRAMEDULLARY OSTEOSARCOMA EXTENT IN PRE-OPERATIVE PLANNING OF CANINE LIMB-SALVAGE PROCEDURES

The objective of this work was to compare the accuracy of radiographs and magnetic resonance imaging (MRI) for estimating appendicular osteosarcoma margins. The accuracy of computed tomography (CT) and bone scintigraphy was also assessed when these studies were available. Eight dogs with appendicular osteosarcoma underwent radiographic and MRI of affected limbs. In addition, bone scintigraphy was performed in six dogs and CT examination was performed in five dogs. Two observers jointly measured tumor length on all imaging studies. Correlative gross and histologic evaluation of all affected limbs was performed to determine tumor extent as measured from the nearest articular surface. Results from imaging studies were compared to gross and microscopic morphometry findings to determine the accuracy of each modality for determining tumor boundaries. MRI images were accurate with a mean overestimation of actual tumor length of 3 +/- 13%. T1-weighted non-contrast images were superior in identifying intramedullary tumor margins in most instances whereas contrast-enhanced images provided supplemental information in two dogs. Lateromedial and craniocaudal radiographs overestimated tumor length by 17 +/- 28% and 4 +/- 26%, respectively. Scintigraphy and CT overestimated tumor margins by 14 +/- 28% and 27 +/- 36%, respectively. MRI appears to be an accurate diagnostic imaging modality in determining intramedullary osteosarcoma boundaries. MRI should be considered as part of a pre-operative assessment of appendicular osteosarcoma, particularly when a limb-sparing procedure is contemplated.     

Functional outcome in dogs after surgical treatment of caudal lumbar intervertebral disk herniation.

Caudal lumbar disk herniations (i.e., third lumbar [L3] to seventh lumbar [L7] intervertebral spaces) represent approximately 15% of surgically treated thoracolumbar disk herniations in dogs. A retrospective case-control study was conducted to determine the postoperative outcome of this subset of dogs in the authors' neurosurgical practice. Medical records (1985 through 1996) were reviewed for dogs with caudal lumbar disk herniation confirmed at surgery. Thirty-six cases were identified. For each case, two dogs that underwent surgical treatment for upper motor neuron thoracolumbar disk herniation (tenth thoracic [T10] to L3 intervertebral spaces) were selected as controls. Probabilities of functional recovery for cases and controls were 81% and 85%, respectively (p value of 0.49). In dogs with caudal lumbar disk herniation, complete sensorimotor loss was the only significant predictor of functional recovery (p value of 0.005). Disk herniations that occur at the thoracolumbar junction and those that occur in the caudal lumbar region should not be considered to be different in terms of surgical treatment and postoperative outcome. The lower motor neuron signs that often accompany caudal lumbar disk herniation reflect the site of spinal cord injury and do not necessarily predict a poor prognosis.     

Influence of intervertebral disc fenestration at the herniation site in association with hemilaminectomy on recurrence in chondrodystrophic dogs with thoracolumbar disc disease: a prospective MRI study

Objective— To describe the influence of fenestration at the disc herniation site on recurrence in thoracolumbar disc disease of chondrodystrophoid dogs.
Study Design— Prospective clinical study.
Animals— Chondrodystrophic dogs (n=19).
Methods— Dogs were divided into 2 groups: group 1 (9 dogs) had thoracolumbar disc extrusion (Hansen type I) treated by hemilaminectomy and concomitant fenestration of the affected intervertebral disc and group 2 (10 dogs) had hemilaminectomy without fenestration. All dogs had 3 magnetic resonance imaging (MRI) examinations: preoperatively, immediately postoperatively to assess removal of herniated disc material, and again 6 weeks after surgery.
Results— There were 13 male and 6 female dogs; mean age, 7.1 years. Thoracolumbar disc herniation was confirmed with MRI. Immediate post surgical MRI revealed that the herniated disc removal was complete in all but 1 dog and that fenestration did not lead to complete removal of nucleus pulposus within the intervertebral disc space. On the 3rd MRI examination, none of the group 1 dogs had further disc material herniation at the fenestrated site. Six of the 10 group 2 dogs had a recurrence of herniation leading to clinical signs in 3 dogs (pain in 2 dogs, paresis in 1 dog).
Conclusion— In thoracolumbar disc herniation, fenestration of the affected intervertebral disc space prevents further extrusion of disc material.
Clinical Relevance— Fenestration reduces the risk of early recurrence of disc herniation and associated postoperative complications.     

Magnetic Resonance Imaging in Dogs with Neurologic Impairment Due to Acute Thoracic and Lumbar Intervertebral Disk Herniation

Background: Magnetic resonance imaging (MRI) is a correlate to physical examination in various myelopathies and a predictor of functional outcome.
Objectives: To describe associations among MRI features, neurological dysfunction before MRI, and functional outcome in dogs with disk herniation.
Animals: One hundred and fifty-nine dogs with acute thoracolumbar disk herniation.
Methods: Retrospective case series. Signalment, initial neurological function as assessed by a modified Frankel score (MFS), and ambulatory outcome at hospital discharge and >3 months (long-term) follow-up were recorded from medical records and telephone interview of owners. Associations were estimated between these parameters and MRI signal and morphometric data.
Results: Dogs with intramedullary T2W hyperintensity had more severe pre-MRI MFS (median 2, range 0–4) and lower ambulatory proportion at long-term follow-up (0.76) than those dogs lacking hyperintensity (median MFS 3, range 0–5; ambulatory proportion, 0.93) ( P =.001 and .013, respectively). Each unit of T2W length ratio was associated with a 1.9 times lower odds of long-term ambulation when adjusted for pre-MRI MFS (95% confidence interval 1.0–3.52, P =.05). Dogs with a compressive length ratio >1.31 (which was the median ratio within this population) had more severe pre-MRI MFS (median 3, range 0–5) compared with those with ratios ≤1.31 (median MFS 3, range 0–4; P =.006).
Conclusions and Clinical Importance: MRI features were associated with initial injury severity in dogs with thoracolumbar disk herniation. Based on results of this study, the T2W length ratio and presence of T2W intramedullary hyperintensity appear to be predictive of long-term ambulatory status.     

EVALUATION OF MAGNETIC RESONANCE IMAGING GUIDELINES FOR DIFFERENTIATION BETWEEN THORACOLUMBAR INTERVERTEBRAL DISK EXTRUSIONS AND INTERVERTEBRAL DISK PROTRUSIONS IN DOGS

Four MRI variables have recently been suggested to be independently associated with a diagnosis of thoracolumbar intervertebral disk extrusion or protrusion. Midline intervertebral disk herniation, and partial intervertebral disk degeneration were associated with intervertebral disk protrusion, while presence of a single intervertebral disk herniation and disk material dispersed beyond the boundaries of the intervertebral disk space were associated with intervertebral disk extrusion. The aim of this retrospective, cross‐sectional study was to determine whether using these MRI variables improves differentiation between thoracolumbar intervertebral disk extrusions and protrusions. Eighty large breed dogs with surgically confirmed thoracolumbar intervertebral disk extrusions or protrusions were included. Randomized MRI studies were presented on two occasions to six blinded observers, which were divided into three experience categories. During the first assessment, observers made a presumptive diagnosis of thoracolumbar intervertebral disk extrusion or protrusion without guidelines. During the second assessment they were asked to make a presumptive diagnosis with the aid of guidelines. Agreement was evaluated by Kappa‐statistics. Diagnostic accuracy significantly improved from 70.8 to 79.6% and interobserver agreement for making a diagnosis of intervertebral disk extrusion or intervertebral disk protrusion improved from fair (κ = 0.27) to moderate (κ = 0.41) after using the proposed guidelines. Diagnostic accuracy was significantly influenced by degree of observer experience. Intraobserver agreement for the assessed variables ranged from fair to excellent and interobserver agreement ranged from fair to moderate. The results of this study suggest that the proposed imaging guidelines can aid in differentiating thoracolumbar intervertebral disk extrusions from protrusions.     

Use of the ventrodorsal myelographic view to predict lateralization of extruded disk material in small-breed dogs with thoracolumbar intervertebral disk extrusion: 104 cases (2004-2005)

OBJECTIVE: To determine whether the ventrodorsal myelographic view can be used to accurately predict the circumferential location of extruded disk material in dogs with thoracolumbar intervertebral disk extrusion (IVDE) and to describe paradoxical contrast obstruction (PCO). DESIGN: Retrospective case series. ANIMALS:104 dogs with Hansen type I IVDE. Procedures-Ventrodorsal myelographic views were reviewed, and contrast patterns were categorized according to 8 predetermined patterns. Agreement among observers was compared, and the predicted location of extruded disk material was compared with surgical findings. RESULTS: Agreement regarding myelographic pattern and location of extruded disk material was moderate (kappa = 0.74 and 0.80, respectively) among the 4 observers. Ninety-three (89%) dogs had myelographic evidence of lateralized extrusion, and in 83 of the 93 (89%), predicted location of extruded disk material matched the surgically confirmed location. In 33 of the 40 (83%) dogs with bilateral contrast column gaps of unequal length, disk material was found to be located on the side with the shorter, rather than the longer, contrast gap, a phenomenon described as PCO. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that the ventrodorsal myelographic view could be used to predict the circumferential location of extruded disk material in dogs with thoracolumbar IVDE more often than previously reported. The PCO phenomenon may be useful in determining the side of lateralization when contrast material does not outline the extruded disk material.     

MYELOGRAPHY VS. COMPUTED TOMOGRAPHY IN THE EVALUATION OF ACUTE THORACOLUMBAR INTERVERTEBRAL DISK EXTRUSION IN CHONDRODYSTROPHIC DOGS

Myelography and/or computed tomography (CT) are commonly used to evaluate acute intervertebral disk extrusion in chondrodystrophic dogs. The purpose of this study was to evaluate the sensitivity of myelography and two different CT protocols in determining level and lateralization of acute thoracolumbar intervertebral disk extrusion in comparison with surgical findings, investigate interobserver variability, and determine examination duration times. Results of conventional CT, helical CT, and myelography were compared with surgical findings in 19 chondrodystrophic dogs with acute thoracolumbar intervertebral disk extrusion. Agreement among investigators was determined for different imaging modalities, and examination times were recorded. In the diagnosis of level of disk extrusion there was agreement of myelography, conventional CT, and helical CT with surgical findings in 94.7%, 100%, and 94.7% of dogs, respectively ( P =0.144). In the diagnosis of level and lateralization of disk extrusion there was agreement of myelography, conventional CT, and helical CT with surgical findings in 78.9%, 87.4%, and 85.3% of dogs, respectively ( P =0.328). Interobserver agreement was very good for all imaging modalities (myelography κ=0.87; conventional CT κ=0.86; helical CT κ=0.95). There were significant differences in median examination duration times between helical CT (4 min), conventional CT (8 min), and myelography (32 min) ( P <0.001). Both helical and conventional CT appear to be accurate for evaluation of acute thoracolumbar intervertebral disk extrusion in chondrodystrophic dogs and are faster to perform than myelography.