Association of magnetic resonance assessed disc degeneration and late clinical recurrence in dogs treated surgically for thoracolumbar intervertebral disc extrusions.

BACKGROUND: Radiographic signs of intervertebral disc mineralization are thought to indicate sites of future recurrence of disc extrusion (Hansen type I) but the relationship between evidence of disc degeneration on magnetic resonance imaging (MRI) and future disc extrusion with recurrence of clinical signs has not been examined. OBJECTIVES: To examine the relationship between MRI-assessed degeneration of thoracolumbar intervertebral discs and late recurrence of clinical signs in dogs presented with acute thoracolumbar intervertebral disc extrusion and treated by hemilaminectomy alone. ANIMALS: Ninety-two client-owned dogs presented to 2 referral hospitals between 2009 and 2014. METHODS: Retrospective analysis of association between clinical signs consistent with recurrent thoracolumbar intervertebral disc extrusion and MRI evidence of disc degeneration in dogs undergoing hemilaminectomy for acute thoracolumbar intervertebral disc extrusion. Univariable and multivariable Cox regression analyses were used to explore associations between recurrence of clinical signs and several characteristics of T10-L3 discs at initial diagnosis. RESULTS: Ninety-two cases were included, of which 42 (46%) were Dachshunds and median age was 5.3 years. Clinical signs recurred in 33/92 (36%) dogs. Finding a completely degenerate disc in the T10 to L3 region (in addition to the operated site) at the time of surgery was associated with a hazard ratio of 2.92 (95% confidence interval: 1.37-6.20) for recurrence of clinical signs. CONCLUSIONS AND CLINICAL IMPORTANCE: Our results suggest that in cases of thoracolumbar intervertebral disc extrusion in dogs, recurrence of signs is likely if at least 1 completely degenerate disc in addition to the currently symptomatic disc is visible on MRI.

Intervertebral disc herniation in two coatis (Nasua nasua) and postoperative laminectomy membrane formation.

Magnetic resonance imaging revealed spinal cord compression due to intervertebral disc herniation of Hansen type I and II in the thoracolumbar vertebral column in two middle-aged coatis (Nasua nasua) with chronic progressive paraparesis. Surgical treatment included hemilaminectomy and partial corpectomy in one and dorsal laminectomy in the other coati. Both coatis recovered well after surgery. One showed unremarkable gait 6 and 15 months post surgery, while the other one suffered from recurrence of paraparesis leading to euthanasia because of deterioration of neurological signs 20 months after the first surgery. Necropsy revealed formation of a laminectomy membrane compressing the spinal cord. Histopathological signs of spinal cord injury and findings of degenerative processes in the intervertebral disc were comparable to those described in dogs. In conclusion, this case report shows for the first time that surgical intervention seems to be a useful and safe treatment in chronic intervertebral disc herniation in coatis, but relapses are possible.

The Myth of Fibroid Degeneration in the Canine Intervertebral Disc: A Histopathological Comparison of Intervertebral Disc Degeneration in Chondrodystrophic and Nonchondrodystrophic Dogs.

Since the seminal work by Hans-Jörgen Hansen in 1952, it has been assumed that intervertebral disc (IVD) degeneration in chondrodystrophic (CD) dogs involves chondroid metaplasia of the nucleus pulposus, whereas in nonchondrodystrophic (NCD) dogs, fibrous metaplasia occurs. However, more recent studies suggest that IVD degeneration in NCD and CD dogs is more similar than originally thought. Therefore, the aim of this study was to compare the histopathology of IVD degeneration in CD and NCD dogs. IVDs with various grades of degeneration (Thompson grade I-III, n = 7 per grade) from both CD and NCD dogs were used (14 CD and 18 NCD dogs, 42 IVDs in total). Sections were scored according to a histological scoring scheme for canine IVD degeneration, including evaluation of the presence of fibrocyte-like cells in the nucleus pulposus. In CD dogs, the macroscopically non-degenerated nucleus pulposus contained mainly chondrocyte-like cells, whereas the non-degenerated nucleus pulposus of NCD dogs mainly contained notochordal cells. The histopathological changes in degenerated discs were similar in CD and NCD dogs and resembled chondroid metaplasia. Fibrocytes were not seen in the nucleus pulposus, indicating that fibrous degeneration of the IVD was not present in any of the evaluated grades of degeneration. In conclusion, intervertebral disc degeneration was characterized by chondroid metaplasia of the nucleus pulposus in both NCD and CD dogs. These results revoke the generally accepted concept that NCD and CD dogs suffer from a different type of IVD degeneration, in veterinary literature often referred to as chondroid or fibroid degeneration, and we suggest that chondroid metaplasia should be used to describe the tissue changes in the IVD in both breed types.

Avaliação clínica de cães com doença do disco intervertebral (Hansen tipo I) submetidos à descompressão cirúrgica: 110 casos / Clinical evaluation of dogs with intervertebral disc disease (Hansen type I) submitted to surgical decompression: 110 cases

O objetivo deste estudo foi identificar cães com doença do disco intervertebral toracolombar (Hansen tipo I) submetidos ao tratamento cirúrgico em um serviço de rotina em neurologia de um hospital veterinário universitário no período de 2006 a 2014, e obter informações a respeito da idade, do sexo, da raça, local da extrusão, interpretação da mielografia, avaliação dos graus de disfunção neurológica, recuperação funcional desses cães e observar a ocorrência de recidiva dos sinais clínicos da doença. A raça mais frequente foi Dachshund (69%), seguida dos cães sem raça definida (14,5%). Os locais mais afetados foram entre T12-T13 (31,9%) e L1-L2 (19,1%). Dos 110 cães, 74 (67,3%) tiveram melhora dos sinais clínicos após o procedimento cirúrgico, sendo 54 (49,1%) considerados satisfatórios e 20 (18,2%), parcialmente satisfatórios. Destes cães, seis (8,1%) cães estavam em grau II, 19 (25,7%) em grau III, 35 (47,3%) em grau IV e 14 (18,9%) em grau V. Pode-se concluir que o tratamento cirúrgico promove recuperação funcional satisfatória na maioria dos cães com extrusão de disco toracolombar. O prognóstico para recuperação funcional após o tratamento cirúrgico é tanto melhor quanto menor for o grau de disfunção neurológica e o percentual de recidiva é baixo em animais submetidos a este tipo de terapia.(AU)

The aim of this study was to identify dogs with thoracolumbar intervertebral disc disease (Hansen type I) submitted for surgical treatment on a routine service in neurology in a university veterinary hospital in 2006-2014, and to get information about age, sex, breed, site of extrusion, interpretation of myelography, evaluation of the degree of neurological dysfunction, functional recovery of these dogs, and to verify the recurrence of clinical signs of disease. The most common breed was Dachshund (69%), followed by mixed breed (14.5%). The most affected sites were between T12-T13 (31.9%) and L1-L2 (19.1%). Of the 110 dogs, 74 (67.3%) improved clinical signs after surgery, 54 (49.1%) satisfactory and 20 (18.2%), in part satisfactory. From these dogs, six (8.1%) dogs were in grade II, 19 (25.7%) in grade III, 35 (47.3%) in grade IV, and 14 (18.9%) in grade V. It can be concluded that satisfactory surgical treatment promotes functional recovery in most dogs with thoracolumbar disk extrusion. The prognosis for functional recovery after surgical treatment is better the lower the degree of neurological dysfunction and the recurrence percentage is lower in dogs subjected to this type of therapy.(AU)

Multiple thoracolumbar partial lateral corpectomies in 17 dogs. / Multiple thorakolumbale partielle laterale Korpektomien bei 17 Hunden.

OBJECTIVE: To report feasibility and outcome of multiple thoracolumbar partial lateral corpectomies (TLPLCs) in dogs with predominantly ventral spinal cord compression caused by intervertebral disc disease (IVDD) in the light of reported decreased spinal stability following single TLPLC. Material und methods: In a retrospective study the records of dogs treated by multiple TLPLCs for ventral spinal cord compression caused by Hansen type I or type II IVDD were reviewed. Presurgical spinal cord compression and postsurgical decompression, as well as slot dimensions were determined based on computed tomography (CT)-myelography images. Neurological outcome was assessed based on repetitive examinations applying a modified Frankel Score as well as on an owner questionnaire. RESULTS: Seventeen dogs with a mean body weight of 20.3 kg (range 4.0-49.0 kg) were included. Fourteen dogs had two TLPLCs, two dogs had three TLPLCs and one dog had four TLPLCs performed. The mean slot depth was 63% of entire vertebral body width, the mean slot height was 29% of the entire vertebral body height, the mean slot length was 25% of the entire vertebral body length and the mean residual vertebral interslot length between two adjacent TLPLCs was 55% of the vertebral body length. At reevaluation 4 weeks after surgery, 6/17 dogs (35.3%) had the same modified Frankel Score as before surgery, whereas 11/17 dogs (64.7%) showed a neurological improvement. According to the owners 78.5% of dogs were walking normally within 6 months after surgery. The mean survival time of 16 dogs, where follow-up was available, was 951 days. CONCLUSION AND CLINICAL RELEVANCE: Multiple spinal cord compressions caused by IVDD can be eliminated by multiple, even consecutive, TLPLCs without the risk of a clinically significant risk of spinal instability.

Inflammatory profiles in canine intervertebral disc degeneration.

BACKGROUND: Intervertebral disc (IVD) disease is a common spinal disorder in dogs and degeneration and inflammation are significant components of the pathological cascade. Only limited studies have studied the cytokine and chemokine profiles in IVD degeneration in dogs, and mainly focused on gene expression. A better understanding is needed in order to develop biological therapies that address both pain and degeneration in IVD disease. Therefore, in this study, we determined the levels of prostaglandin E2 (PGE2), cytokines, chemokines, and matrix components in IVDs from chondrodystrophic (CD) and non-chondrodystrophic (NCD) dogs with and without clinical signs of IVD disease, and correlated these to degeneration grade (according to Pfirrmann), or herniation type (according to Hansen). In addition, we investigated cyclooxygenase 2 (COX-2) expression and signs of inflammation in histological IVD samples of CD and NCD dogs. RESULTS: PGE2 levels were significantly higher in the nucleus pulposus (NP) of degenerated IVDs compared with non-degenerated IVDs, and in herniated IVDs from NCD dogs compared with non-herniated IVDs of NCD dogs. COX-2 expression in the NP and annulus fibrosus (AF), and proliferation of fibroblasts and numbers of macrophages in the AF significantly increased with increased degeneration grade. GAG content did not significantly change with degeneration grade or herniation type. Cytokines interleukin (IL)-2, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, immune protein (IP)-10, tumor necrosis factor (TNF)-α, and granulocyte macrophage colony-stimulating factor (GM-CSF) were not detectable in the samples. Chemokine (C-C) motif ligand (CCL)2 levels in the NP from extruded samples were significantly higher compared with the AF of these samples and the NP from protrusion samples. CONCLUSIONS: PGE2 levels and CCL2 levels in degenerated and herniated IVDs were significantly higher compared with non-degenerated and non-herniated IVDs. COX-2 expression in the NP and AF and reactive changes in the AF increased with advancing degeneration stages. Although macrophages invaded the AF as degeneration progressed, the production of inflammatory mediators seemed most pronounced in degenerated NP tissue. Future studies are needed to investigate if inhibition of PGE2 levels in degenerated IVDs provides effective analgesia and exerts a protective role in the process of IVD degeneration and the development of IVD disease.

"Disk extension beyond the interspace": an investigation into an alternative nomenclature in diagnostic imaging for displaced canine intervertebral disk material.

BACKGROUND: Displacement of canine intervertebral disk material can be seen directly in diagnostic imaging modalities such as magnetic resonance imaging and computed tomographic imaging. Canine intervertebral disk herniation can be differentiated into Hansen type 1 and 2 categories by clinical appearance, but anular- and nuclear disk material cannot be distinguished in computed tomographic images. Therefore, we hypothesized that the "Disk extension beyond the interspace"-nomenclature that describes the displacement by the disk contour might aid diagnosis. The aim of this study was to test the reliability of the "Disk extension beyond the interspace"-nomenclature in the evaluation of canine intervertebral disks via magnetic resonance and computed tomographic imaging. RESULTS: Magnetic resonance and computed tomographic images of 144 intervertebral disks of 43 dogs were evaluated by 3 observers with different degrees of experience from 2 institutions retrospectively. A substantial intraobserver agreement was found, while interobserver agreement was fair to moderate with significant differences in evaluation. Comparison of imaging methods showed a fair to moderate agreement without statistically significant differences in evaluation. CONCLUSIONS: DEBIT-nomenclature cannot be recommended for veterinary clinical usage yet. The largest variability was found in the evaluation of the bulged canine intervertebral disk. The observers' experience and the imaging method influenced DEBIT- evaluation only slightly, while training and working at different institutions influenced DEBIT-evaluation strongly.

Hemilaminectomy for thoracolumbar Hansen Type I intervertebral disk disease in ambulatory dogs with or without neurologic deficits: 39 cases (2008-2010).

OBJECTIVE: To describe prognostic factors, outcome, and time to recovery among ambulatory dogs having hemilaminectomy for Hansen Type I intervertebral disk disease. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 38; 39 hemilaminectomies). METHODS: Medical records (January 2008-May 2010) on all dogs that had hemilaminectomy for Hansen Type I intervertebral disk disease were reviewed. Records for dogs that were ambulatory preoperatively were analyzed for signalment, duration and severity of signs, presence of neurologic deficits, and postoperative outcome. Dogs were categorized based on Frankel score and subcategorized by their level of conscious proprioceptive (CP) deficit. Postoperatively, time to ambulation and to regain normal CP responses was recorded. Results for each group were compared using a χ(2) test and considered significant when P < .05. Recovery times were analyzed using a Cox proportional hazards model. RESULTS: Seven dogs were categorized as modified Frankel grade I preoperatively and 32 dogs as grade II with varying levels of deficits (1 of these dogs had previously been operated as grade II and was reoperated again as grade II). Increasing degree of CP deficit preoperatively was significantly correlated with longer time to ambulation (P = .005) as well as longer time to CP normal (P = .01). Duration of signs was not significantly correlated with time to ambulation or neurologic recovery for either grade I or II dogs. CONCLUSIONS: Most dogs recovered well with surgical decompression. Increasing degree of deficits preoperatively is significantly correlated with longer recovery time.

Intervertebral disc disease in dogs - part 2: comparison of clinical, magnetic resonance imaging, and histological findings in 74 surgically treated dogs.

The relationship between intervertebral disc (IVD) disease and IVD degeneration remains unclear. The aim of the present study was to compare the clinical severity of IVD herniation (IVDH), determined with a neurological grading system, with findings of magnetic resonance imaging (MRI) and histology using grading systems for IVD degeneration in chondrodystrophic (CD; n=37) and non-chondrodystrophic (NCD; n=37) dogs. This study is the second part of a two-part investigation, where the first part involved the development and validation of a histological grading scheme for classification of canine IVD degeneration. IVD degeneration graded on MRI correlated significantly with IVD degeneration graded on histology, but not with pre-operative clinical signs. Hansen type 1 hernias were more common in the cervical and thoracolumbar segments and Hansen type 2 hernias were more common in the lumbosacral segment. Type 1 hernias occurred more often in CD dogs than in NCD dogs, and CD dogs were clinically more severely affected than NCD dogs. The grade of IVD degeneration on MRI was higher in CD dogs than in NCD dogs, but there was no difference between dogs with type 1 and type 2 hernias. No significant differences in histological grade were found between CD and NCD dogs or between type 1 and type 2 hernias. It was possible to conclude that IVD degeneration did not correlate with the neurological severity of IVDH. The extent of degeneration identified on MRI correlated with degeneration seen histologically. Although the MRI grading system reflected the severity of IVD degenerative changes as confirmed by histopathology, it appeared less useful in predicting the clinical implications.

Cytologic and histopathologic evaluation of extruded canine degenerate disks.

OBJECTIVE: To describe the cytologic and histopathologic appearance of degenerate disk material in dogs with Hansen type I intervertebral disk disease (IVDD). STUDY DESIGN: Case series. ANIMALS: Dogs (n=45) that had surgical intervention for Hansen type I IVDD (January-November 2007). METHODS: Impression smears and histopathologic sections were prepared from surgically removed degenerate disk material. All slides were evaluated for overall cellularity, quantity and attributes of extracellular matrix, types of cells present, and their cytomorphology. Histopathologic sections were also examined for presence of neovascularization and hemorrhage. RESULTS: Cytologically, 11 of 45 samples consisted of only extracellular matrix, 30 had evidence of inflammation, and 20 contained dysplastic spindloid cells. Histologically, hyaline cartilage predominated in 35 of 45 samples, fibrocartilage in 4, and spindloid cells in 6; 37 of 45 were inflamed, 37 were hemorrhagic, and 13 had neovascularization. CONCLUSIONS: The cytologic and histopathologic appearance of extruded degenerate disk material in dogs is variable and can include dysplastic spindloid cells. CLINICAL RELEVANCE: The variability in cytologic findings and frequent presence of dysplastic spindloid cells suggest that cytology alone may not be a reliable tool to differentiate degenerate canine disk material from a mesenchymal neoplasm.