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.

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.

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.

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.