The vacuum phenomenon in intervertebral disc disease of dogs based on computed tomography images

Sternal Abnormalities on Thoracic Radiographs of Dogs and Cats

Evaluation of the sternum is part of the routine examination of small animal thoracic radiographs. However, descriptions on frequency and type of abnormalities are lacking. This retrospective observational study aimed to describe abnormal radiographic findings of the sternum in a cross-section of client-owned dogs and cats undergoing thoracic radiography between 1 January 2019 and 1 January 2021 for reasons unrelated to diseases of the sternum. The study population consisted of 777 dogs (mean age, 7.3 ± 3.9 years) and 183 cats (mean age, 7.3 ± 5.1 years). Sternal abnormalities were observed in 189/777 (24%) dogs and 53/183 (29%) cats, mostly around the intersternebral cartilages, accounting for 32/80 (40%) dogs and 20/35 (57%) cats. This was followed by an abnormal number of sternal segments (8% dogs, range 3–9 sternebrae; 15% cats, range 7–9 sternebra). Pectus excavatum was observed in 6/777 (0.8%) dogs and 6/183 (3%) cats, and pectus carinatum in 18/777 (2%) dogs and 2/183 (1%) cats. Post-traumatic changes, such as subluxation, were observed in nine dogs (1.1%) and three cats (1.6%). Presumed prostatic carcinoma metastasis and malignant lymphoma were observed in two dogs (0.2%). Incidental radiographic sternal abnormalities are common in cats and dogs but mostly of unknown clinical relevance.

Computed tomography features of discospondylitis in dogs

BACKGROUND

Computed tomography (CT) findings of dogs with discospondylitis have not been widely described despite increased availability of this imaging modality.

OBJECTIVES

Describe the CT features of discospondylitis in a population of clinically affected dogs with discospondylitis diagnosed by magnetic resonance imaging (MRI).

ANIMALS

Forty-one dogs (63 affected discs) with MRI-identified discospondylitis presented to a single referral hospital between 2012 and 2022.

METHODS

Retrospective, single center, descriptive case series with analysis of MRI-identified discospondylitis sites and concomitant CT imaging. Computed tomographic features of MRI-affected sites including intervertebral disc space (IVDS), endplates, vertebral body, epidural space and paraspinal tissues were described.

RESULTS

The most frequently found changes were: (1) endplate involvement (87.3%) most frequently bilateral (94.5%), with erosion (61.9%) and multifocal osteolysis (67.3%); (2) periosteal proliferation adjacent to the IVDS (73%) and spondylosis (66.7%); and (3) vertebral body involvement (66.7%) involving one-third of the vertebra (85.7%) with multifocal osteolysis (73.5%). Other less prevalent features included an abnormal IVDS (narrowed or collapsed), sclerosis of the adjacent vertebral body or endplates, presence of disseminated idiopathic skeletal hyperostosis or vacuum artifact.

CONCLUSIONS AND CLINICAL IMPORTANCE

We determined that bilateral endplate erosion and periosteal proliferation were very common in dogs with discospondylitis. Careful evaluation of CT in all 3 planes (dorsal, sagittal, transverse) is necessary to identify an affected IVDS. These described CT features can aid in the diagnosis of discospondylitis in dogs but equivocal cases might still require MRI.

Encapsulated gas accumulation in the spinal canal: Pneumorrhachis in two dogs

A 17-year-old mongrel dog and 12-year-old Shiba Inu dog presented with ataxia and paresis of the pelvic limbs, respectively. Gas accumulation within the spinal canal adjacent to the herniated disc was suspected in both cases. Since the gas remained accumulated for a prolonged period, hemilaminectomy was performed to decompress the spinal cord. The bulged external lamina of the dura matter was removed and histopathologically examined. Granulomatous inflammation and hyperplasia of fibrous connective tissues was noted, suggesting that the gas was encapsulated and the fibrous nodules made reabsorption difficult. Clinical signs resolved post-surgery. This is the first report describing histopathological features of pneumorrhachis in dogs. The accumulated gas was successfully removed by surgery. Postoperative course remained uneventful in both cases.

Evaluation of vacuum phenomenon in dogs with coxofemoral degenerative joint disease using computed tomography

Background

Degenerative joint disease (DJD) is a common orthopedic lesion in the coxofemoral joint of canine patients. Concurrent with the sign of degeneration, the vacuum phenomenon (VP), or intra-articular gas, has been observed in several locations in both human and canine patients. A cadaveric study described VP in small breed dogs without DJD but with hip laxity. However, none of the canine VP reports mentioned coxofemoral DJD. Therefore, the aim of this retrospective study was to describe the distribution of coxofemoral VP revealed on computed tomography (CT) imaging in canine patients with DJD.

Results

A total of 282 dogs (564 coxofemoral joints), comprising 142 small, 85 large, and 55 medium breeds, were included in the present study. DJD was found in 31.02% of all dogs. The incidence of DJD was highest in large breed dogs (50%), followed by medium (31.81%) and small (19.36%) breed dogs. In addition, VP was detected with CT using the pulmonary window in 31 joints of 25 dogs that received a diagnosis of hip degenerative disease. VP was found most frequently at the laterodorsal area of the acetabulum. The incidences of VP in large, small, and medium breed dogs were 35.94%, 17.14% and 8.33%, respectively. The presence of coxofemoral VP was significantly and positively correlated with DJD (odds ratio = 17.58, 95% CI 2.32–133.42).

Conclusions

The presence of coxofemoral joint DJD and VP was more likely to be detected in large breed dogs, especially in those with established DJD. CT is an advanced diagnostic imaging modality that can be used to reveal VP lesions, most of which are reported at the laterodorsal acetabulum. Further studies, including comparisons of different patient positions, may reveal more information regarding coxofemoral VP.

Imaging features of discospondylitis in cats

OBJECTIVES

This study describes the imaging features of feline discospondylitis on MRI, comparing them with CT and radiographic findings where available.

METHODS

The medical records of cats diagnosed with discospondylitis, presented to three referring institutions, were reviewed. MRI, CT and radiographic features were assessed by two of the authors independently.

RESULTS

Fourteen sites of discospondylitis were retrospectively identified in 13 cats. The L7-S1 intervertebral disc space (IVDS) was affected in 7/14 (50%) cases. Characteristic MRI features included a hyperintense nucleus pulposus signal on T2-weighted (T2W) imaging (n = 10/14 [71%]) and short tau inversion recovery (STIR) imaging (n = 11/13 [85%]), with contrast enhancement in all (n = 11/11); involvement of adjacent vertebral endplates (n = 11/14 [79%]) and hyperintense neighbouring soft tissue on T2W (n = 11/14 [79%]) and STIR (n = 10/13 [77%]), with contrast enhancement in all (n = 11/11); and the presence of spondylosis deformans (n = 10/14 [71%]). Other features included narrowed or collapsed IVDS (n = 8/14 [57%]), contrast enhancement of vertebral bodies (n = 5/11 [46%]), epidural space involvement (n = 5/14 [36%]), compression of the spinal cord or nerve roots (n = 5/14 [36%]), paraspinal abscessation (n = 3/14 [21%]) and meningeal signal intensity abnormalities with contrast enhancement (n = 5/6 [83%]). These latter findings may indicate secondary focal meningitis. Radiographs were available covering five sites (in four cats) and CT covering three sites (in two cats). The most common radiological features were collapse or narrowing of the affected IVDS (80%) and endplate erosion (60%). No changes suggestive of discospondylitis were identifiable on radiography or CT in two sites (one cat), despite being identifiable on MRI. Repeated radiography in one case did not reveal complete radiological resolution following 9 months of treatment.

CONCLUSIONS AND RELEVANCE

The results of this study indicate consistent MRI features of feline discospondylitis that should be considered in the diagnosis of this condition.

Vertebral column deformity with curved cross-stitch vertebrae in Norwegian seawater-farmed Atlantic salmon, Salmo salar L

Pathological changes in the vertebral column of farmed Atlantic salmon in Norway have been reported since the 1990s. Based on the characteristic radiographic findings, we here present a vertebral column deformity named "curved cross-stitch vertebrae" that mainly affects the middle aspect of the vertebral column. Sixty fish, from the west/northwest coast of mid-Norway, were sampled at slaughter and examined by radiography, computed tomography (CT), necropsy, macrophotography, and histology. The vertebral deformities were radiographically graded as mild, moderate, or marked. The main differences between these grades of changes were defined by increased curving of the peripheries of endplates, reduced intervertebral spaces, and vertical displacement of the vertebrae. The curved rims of endplates were located peripheral to a continuous and approximately circular borderline. The CT studies revealed small, multifocal, hypo-attenuating, round to crescent-shaped areas in the notochord, compatible with the presence of gas. Additionally, histology revealed that the axial parts of endplates had circular zones with perforations, through which either notochordal tissue prolapsed into the vertebrae or vascularized fibrochondroid proliferations extended from the vertebrae into the notochord. Inflammation was present in many vertebral bodies. To the best of our knowledge, this is the first report of gas in the notochord of fish.

Equine cervical intervertebral disc degeneration is associated with location and MRI features

Morphology of the equine cervical intervertebral disc is different from that in humans and small companion animals and published imaging data are scarcely available. The objectives of this exploratory, methods comparison study were (a) to describe MRI features of macroscopically nondegenerated and degenerated intervertebral discs (b) to test associations between spinal location and macroscopic degeneration or MRI‐detected annular protrusion and between MRI‐detected annular protrusion and macroscopic degeneration, and (c) to define MRI sequences for characterizing equine cervical intervertebral disc degeneration. Ex vivo MRI of intervertebral discs was performed in 11 horses with clinical signs related to the cervical region prior to macroscopic assessment. Mixed‐effect logistic regression modeling included spinal location, MRI‐detected annular protrusion, and presence of macroscopic degeneration with “horse” as random effect. Odds ratio and 95% confidence interval were determined. Reduced signal intensity in proton density turbo SE represented intervertebral disc degeneration. Signal voids due to presence of gas and/or hemorrhage were seen in gradient echo sequences. Presence of macroscopic intervertebral disc degeneration was significantly associated with spinal location with odds being higher in the caudal (C5 to T1) versus cranial (C2 to C5) part of the cervical vertebral column. Intervertebral discs with MRI‐detected annular protrusion grades 2‐4 did have higher odds than with grade 1 to have macroscopic degeneration. It was concluded that MRI findings corresponded well with gross macroscopic data. Magnetic resonance imaging of the equine cervical intervertebral disc seems to be a promising technique, but its potential clinical value for live horses needs to be explored further in a larger and more diverse population of horses.

Epidural Gas Accumulation in Connection with Canine Degenerative Lumbosacral Disease

Three dogs were presented with lumbosacral hyperesthesia. Computerized tomography scans were performed in all the cases, and magnetic resonance imaging was also performed in cases 1 and 3. There was intervertebral disc (IVD) protrusion causing nerve root compression and epidural gas accumulation in all the three cases. The gas-filled cystic structures in cases 1 and 3 were within the spinal canal; in case 2, the gas was within the disc protrusion. The IVD vacuum phenomenon is relatively common in dogs, but the formation of an epidural gas accumulation in cases of a lumbar disc protrusion is rare. The clinical significance of these epidural gas accumulations is unknown. Two of the dogs were treated surgically, improved after surgery, and showed no signs of pain in the follow-up examinations.

Assessment of interobserver agreement and use of selected magnetic resonance imaging variables for differentiation of acute noncompressive nucleus pulposus extrusion and ischemic myelopathy in dogs

OBJECTIVE To evaluate interobserver agreement for features used in presumptive diagnosis of acute noncompressive nucleus pulposus extrusion (ANNPE) or ischemic myelopathy by MRI, compare findings on postcontrast T1-weighted (T1W) MRI sequences with fat saturation (FS) for the 2 conditions, and determine whether length and directional patterns of hyperintensity of the intramedullary spinal cord on T2-weighted (T2W) fast spin echo (FSE) MRI sequences differ between dogs with these diseases. DESIGN Retrospective, observational study. ANIMALS 20 dogs with clinical signs compatible with ANNPE (n = 14) or ischemic myelopathy (6). PROCEDURES 3 observers evaluated MRI data (including T2W FSE, T2W single-shot FSE, and T1W FS sequences) for dogs with a presumptive diagnosis of ischemic myelopathy or ANNPE. Interobserver agreement for variables of interest including presumptive diagnosis was assessed by κ statistic calculations. Associations between diagnosis and variables of interest were assessed with Fisher exact or Cochran-Mantel-Haenszel tests. RESULTS Perfect interobserver agreement (κ = 1 for all comparisons) was found for the presumptive diagnosis of ischemic myelopathy versus ANNPE. Meningeal enhancement on postcontrast T1W FS MRI images and nonlongitudinal directional pattern of intramedullary hyperintensity on T2W FSE images were significantly associated with a diagnosis of ANNPE. Greater length of intramedullary hyperintensity was significantly associated with a diagnosis of ischemic myelopathy. CONCLUSIONS AND CLINICAL RELEVANCE Directional pattern and length of intramedullary hyperintensity on T2W FSE MRI images and enhancement patterns in postcontrast T1W FS sequences may provide important contributions to the criteria currently used in the presumptive diagnosis of ischemic myelopathy versus ANNPE.

[Diagnostic imaging of changes of the canine intervertebral disc]

Intervertebral disc degeneration can cause intervertebral disc herniation. Diagnostic imaging, including radiography, computed tomography and magnetic resonance imaging, is the most important tool in diagnosis. Firstly, an overview of macroscopic and biochemical physiology and pathology of the intervertebral disc will be given. Subsequently, the physics of diagnostic imaging and the appearance of intervertebral disc degeneration and displacement in several imaging methods are described.

[Classification of canine intervertebral disc degeneration using high-field magnetic resonance imaging and computed tomography]

OBJECTIVE

Although the classification of canine intervertebral disc degeneration using magnetic resonance imaging (MRI) has been described in the literature, there is no such classification using computed tomographic imaging. Because computed tomography (CT) is a frequently used diagnostic imaging tool in veterinary medicine, the aim of this study was the introduction and validation of such a scoring system. T2-weighted magnetic resonance images were available for comparative analysis.

MATERIAL AND METHODS

A total of 43 dogs were examined using CT and MRI. Image data records of 144 intervertebral discs were blinded, randomized and evaluated twice by three observers. CT data were analyzed using a self-developed scoring system, while MRI data sets were evaluated using the Pfirrmann scoring system. Intra- and interobserver agreement were determined using Statistical Analysis Software (SAS).

RESULTS

Intra- and interobserver agreement were mostly substantial in the Pfirrmann (0.58-0.77) and self-developed (0.60-0.81) scoring systems. A slight agreement was found between both classification systems (κ scores 0.26-0.29).

CONCLUSION AND CLINICAL RELEVANCE

The self-developed scoring system allows a reliable assessment of canine intervertebral disc degeneration using CT imaging. Therefore, further diagnostic and prognostic information can be obtained. Degenerative changes in the intervertebral discs could be identified at an earlier stage when using MRI in comparison with CT.

Spinal dermoid sinus in a Dachshund with vertebral and thoracic limb malformations

BACKGROUND

Dermoid sinus is an uncommon epithelial-lined fistula that may be associated with vertebral malformations. In humans, Klippel-Feil syndrome (KFS) is a rare condition characterized by congenital cervical vertebral fusion and may be associated with other developmental defects, including dermoid sinus. The present case report describes an adult Dachshund with cervical and cranial thoracic vertebral malformations as well as thoracic limb malformations resembling KFS with a concurrent type IV dermoid sinus.

CASE PRESENTATION

A 1.5 year-old Dachshund with congenital thoracic limbs deformities and cervical-thoracic vertebral malformations presented with cervical hyperesthesia, rigidity of the cervical musculature and tetraparesis. Neurologic, radiographic, and computed tomography (CT) (2D, 3D, CT fistulography) examinations revealed skeletal anomalies, a dermoid sinus in the cranial thoracic region and epidural gas within the vertebral canal. Surgical resection and histopathological evaluation of the sinus tract were performed and confirmed a type IV dermoid sinus. The clinical signs progressively recovered postoperatively, and no recurrent signs were observed after 6 months of follow-up.

CONCLUSIONS

Cervical vertebral malformations associated with limbs anomalies have not been reported in dogs and may represent a condition similar to KFS in humans. KFS can occur concurrently with other congenital conditions including dermoid sinus and should be included among the complex congenital anomalies described in dogs.