Prospective randomized trial comparing relapse rates in dogs with steroid-responsive meningitis-arteritis treated with a 6-week or 6-month prednisolone protocol.

BACKGROUND: Traditionally, 6-month courses of prednisolone are used to treat steroid-responsive meningitis-arteritis (SRMA), but this medication is associated with adverse effects that can lead to poor quality of life. HYPOTHESIS/OBJECTIVES: Resolution of clinical signs and rate of relapse of SRMA would not be significantly different between a 6-month prednisolone protocol and a 6-week protocol. ANIMALS: Forty-four hospital cases from multiple referral centers in the United Kingdom (2015-2019). Twenty of 44 were treated with the 6-month protocol and 24/44 with the 6-week protocol. METHODS: Prospective, randomized trial with 12-month follow-up. The same prednisolone protocol reinitiated in the event of relapse. Analysis of relapses with binary logistic and Poisson regression modeling. RESULTS: All cases responded to their treatment protocol. Relapses occurred in 6/20 (30%) of the 6-month protocol and 9/24 (38%) of the 6-week protocol. There was no statistical difference in the incidence risk of at least 1 relapse between the 2 groups (odds ratio = 1.40; 95% confidence interval [CI], 0.40-4.96, P = 0.60). Among the 15 dogs that relapsed, 10/15 (67%) relapsed once, 3/15 (20%) relapsed twice, and 2/15 (13%) relapsed 3 times. No statistical difference was detected in the incidence rate ratio (IRR) of total relapse events between the 2 groups (IRR = 1.46; 95% CI, 0.61-3.48; P = 0.40). CONCLUSIONS AND CLINICAL IMPORTANCE: "Short" 6-week prednisolone protocols could be used to treat SRMA, thereby presumably reducing the duration and severity of prednisolone's adverse effects.

Accuracy and safety of freehand vs. end-on fluoroscopic guided drill-hole placement in canine cadaveric thoracic, lumbar and sacral vertebrae.

Objective: To develop and evaluate the safety and accuracy of an open, end-on fluoroscopic guided (EOFG) drill hole position technique in canine cadaveric spinal surgery, in comparison to a traditional free-hand (FH) drilling technique. Study design: Cadaveric comparison study. Animals: Canine cadaveric vertebral columns (n = 4). Methods: Computed tomography (CT) scans were performed for in-silico planning. Ideal implant purchase depth and angulations were determined from previously published data. Plans for end-on fluoroscopic guided drill holes included angled reconstructions in thick slab mode to mimic fluoroscopic images. Following surgical preparation of T8 to S2, holes were drilled by one of two experienced surgeons randomized evenly by operated side, surgeon, and technique. C-arm fluoroscopy was utilized for the end-on technique. CT was repeated after the procedures. Safety was determined categorically using a modified Zdichavsky classification and "optimal" placement was compared between techniques. Continuous data for drill-hole accuracy was calculated as angle and depth deviations from the planned trajectories. Data sets were analyzed at both univariable and multivariable levels with logistic regression analysis. Results: Drill hole safety was categorized as optimal (modified Zdichavsky classification 1) in 51/60 (85%) of drill holes using EOFG and 33/60 (55%) using FH (P < 0.001) techniques. There were no "unsafe" holes (modified Zdichavsky classification 3a). Optimal drill hole placement was significantly associated with the EOFG technique and use of the largest cadaver, and was significantly less likely within the thoracic region. Mean angle and depth deviations were significantly lower with the EOFG technique. Angle deviations were significantly lower for EOFG in the lumbar region, whereas bone purchase deviations were significantly lower for EOFG in both the thoracic and lumbar regions. The mean time taken to drill the hole was significantly longer for the EOFG technique. Conclusion: Optimal drill hole placement was significantly more likely with the EOFG technique and improved the accuracy of bone purchase in the thoracic region. Clinical significance: The EOFG technique shows promise for translation into a clinically setting, potentially improving implant purchase and therefore stabilizing construct strength, whilst potentially reducing the likelihood of neurovascular injury and need for surgical revision.

Comparison of standard T2-weighted turbo spin echo and volumetric interpolated breath-hold examination magnetic resonance imaging sequences in the assessment of articular process dysplasia in Pug dogs with thoracolumbar myelopathy.

Introduction: A retrospective study to compare the classification, as normal, hypoplastic or aplastic, of thoracic (T10-T13) caudal articular process (CAP) morphology in Pug dogs with a thoracolumbar myelopathy as normal, hypoplastic or aplastic, between T2 weighted Turbo Spin Echo (T2W-TSE), in sagittal and transverse planes, and Volumetric Interpolated Breath-hold Examination (VIBE) Magnetic Resonance Imaging (MRI) sequences, in comparison to Computed Tomography (CT). We hypothesized a stronger agreement for VIBE in comparison to T2W-TSE. Results: Diagnostic accuracy of T2W-TSE was inferior to VIBE for aplastic (60%, 95% CI 0.561-0.639 vs. 78%, 95%CI 0.744-0.815) hypoplastic (44%, 95%CI 0.427-0.452 vs. 62.5%, 95%CI 0.595-0.655) and normal CAP (70%, 95%CI 0.655-0.744 vs. 87%, 95%CI 0.848-0.892). Superior accuracy of classification using VIBE vs. T2W-TSE sequences using the McNemar Chi squared test was significant for aplastic (p = 0.0002) and normal CAP (p = 0.004). VIBE sequences had a sensitivity of 96% and specificity of 75% to detect CAP abnormality and with T2W-TSE imaging sensitivity 81% and specificity of 75%. Discussion: Three-dimensionally reconstructable VIBE sequences were significantly more accurate than traditional T2W-TSE MRI sequences in classifying CAP morphology, which should reduce the need for CT for pre-operative assessment.

Instrumented cervical fusion using patient specific end-plate conforming interbody devices with a micro-porous structure in nine dogs with disk-associated cervical spondylomyelopathy.

Objective: To report the medium and long-term outcome of nine dogs with disk-associated cervical spondylomyelopathy (DA-CSM), treated by instrumented interbody fusion using patient specific end-plate conforming device that features a micro-porous structure to facilitate bone in-growth. Study design: A retrospective clinical study. Animals: Nine medium and large breed dogs. Methods: Medical records at two institutions were reviewed between January 2020 and 2023. Following magnetic resonance imaging (MRI) diagnosis of DA-CSM, pre-operative computed tomography (CT) scans were exported to computer software for in-silico surgical planning. Interbody devices were 3D-manufactured by selecting laser melting in titanium alloy. These were surgically implanted at 13 segments alongside mono-or bi-cortical vertebral stabilization systems. Follow-up included neurologic scoring and CT scans post-operative, at medium-term follow up and at long-term follow-up where possible. Interbody fusion and implant subsidence were evaluated from follow-up CT scans. Results: Nine dogs were diagnosed with DA-CSM between C5-C7 at a total of 13 operated segments. Medium-term follow up was obtained between 2 and 8 months post-operative (3.00 ± 1.82 months). Neurologic scoring improved (p = 0.009) in eight of nine dogs. Distraction was significant (p < 0.001) at all segments. Fusion was evident at 12/13 segments. Subsidence was evident at 3/13 operated segments but was only considered clinically relevant in one dog that did not improve; as clinical signs were mild, revision surgery was not recommended. Long-term follow up was obtained between 9 and 33 months (14.23 ± 8.24 months); improvement was sustained in 8 dogs. The dog that suffered worsened thoracic limb paresis at medium-term follow up was also diagnosed with immune-mediated polyarthropathy (IMPA) and was euthanased 9 months post-operative due to unacceptable side-effects of corticosteroid therapy. Conclusion: End-plate conforming interbody devices with a micro-porous structure were designed, manufactured, and successfully implanted in dog with DA-CSM. This resulted in CT-determined fusion with minimal subsidence in the majority of operated segments. Clinical significance: The technique described can be used to distract and fuse cervical vertebrae in dogs with DA-CSM, with favorable medium-and long-term outcomes.

Surgical management of traumatic atlantoaxial subluxation in two cats.

CASE SERIES SUMMARY: We describe here the surgical management of two pure breed cats with traumatic atlantoaxial subluxation. One cat was ambulatory tetraparetic on presentation and the second was tetraplegic, both with cervical spinal pain and acute onset of paresis with subsequent deterioration. MRI was performed in both cases, demonstrating spinal cord injury. Flexed lateral cervical radiographs were needed to confirm atlantoaxial subluxation in one case. CT was performed for surgical planning and surgical stabilisation was achieved with threaded pins and polymethyl methacrylate (PMMA) cement; odontoidectomy was required in one case. Both cats showed improvement postoperatively, with no complications or deterioration seen. Following surgery, one cat made a complete recovery; however, the second cat retained significant deficits. RELEVANCE AND NOVEL INFORMATION: We present the first report of surgically managed atlantoaxial subluxation of traumatic aetiology in cats, and report its occurrence in two novel breeds for this disease, Ragdoll and Persian. One case required odontoidectomy due to previous fracture and malunion of the odontoid process of the axis; both cases underwent surgical stabilisation of the atlantoaxial joint utilising multiple threaded pins and PMMA cement without transarticular implants - a technique that has not been previously reported in cats.

Limited dorsal myeloschisis in three cats: a distinctive form of neural tube defect.

CASE SERIES SUMMARY: The aim of this case series was to describe the clinical presentation, imaging findings and histopathology of three cats with limited dorsal myeloschisis (LDM). The history, examination and MRI sequences were reviewed in three cases presented to a single referral hospital. The surgery report and histopathology were described in two cases. All cats were young (10 weeks old, 5 months old, 4 years old), presenting with varying degrees of progressive paraparesis. All had a midline skin defect overlying the spinal column that was either sunken or saccular, containing fluid thought to be cerebrospinal fluid. MRI sequences demonstrated tissue extending from the dura through an overlying bifid spinous process and attached to the dermis, with associated spinal cord tethering, atrophy and syringomyelia. Lesions were located at L2-L3, T8-T9 and L4. Histopathology described a fibroneural stalk with a glio-ependymal lining, surrounded by glial nests and nerve fibres. The youngest and most severely affected was euthanased, while the other two underwent surgery. Both regained independent ambulation with persistent paraparesis; however, one required ongoing management of urinary incontinence. RELEVANCE AND NOVEL INFORMATION: LDM is a primary neural tube defect that may result in neurological deficits, including bladder dysfunction, and is characterised by a fibroneural stalk between the dermis and the spinal cord. Distinct MRI features, such as a visible intrathecal tract, dorsally tethered cord and syringomyelia, help distinguish this condition from the clinically similar dermoid sinus. The presence of progressive neurological signs, with a palpable midline defect overlying the affected spinal cord segment, may raise suspicion for this clinical entity in veterinary patients.

Magnetic resonance image findings in pug dogs with thoracolumbar myelopathy and concurrent caudal articular process dysplasia.

BACKGROUND: A retrospective case series study was undertaken to describe the magnetic resonance imaging (MRI) findings in Pug dogs with thoracolumbar myelopathy and concurrent caudal articular process (CAP) dysplasia. Electronic clinical records were searched for Pug dogs who underwent MRI for the investigation of a T3-L3 spinal cord segment disease with subsequent confirmation of CAP dysplasia with computed tomography between January 2013 and June 2017. Clinical parameters age, gender, neuter status, body weight, urinary or faecal incontinence, severity and duration of clinical signs were recorded. MRI abnormalities were described. Univariable non-parametric tests investigated the association between the clinical parameters and evidence of extra- or intra-dural spinal cord compression on MRI. RESULTS: 18 Pug dogs were included. The median age was 106 months with median duration of clinical signs 5 months. All presented with variable severity of spastic paraparesis and ataxia; 50% suffered urinary/faecal incontinence. In all cases, MRI revealed a focal increase in T2-weighted signal intensity within the spinal cord at an intervertebral level where bilateral CAP dysplasia was present; this was bilateral aplasia in all but one case, which had one aplastic and one severely hypoplastic CAP. MRI lesions were associated with spinal cord compression in all but one case; intervertebral disc protrusion resulted in extra-dural compression in 10 (56%) cases; intra-dural compression was associated with a suspected arachnoid diverticulum in 4 (22%) cases and suspected pia-arachnoid fibrosis in 3 cases (17%). There was no association between clinical parameters and a diagnosis of intra-dural vs extra-dural compression. CAP dysplasia occurred at multiple levels in the T10-13 region with bilateral aplasia at T11-12 most often associated with corresponding spinal cord lesions on MRI. CONCLUSIONS: All Pugs dogs in this study were presented for chronic progressive ambulatory paraparesis; incontinence was commonly reported. Although intervertebral disc disease was the most common radiologic diagnosis, intra-dural compression associated with arachnoid diverticulae/fibrosis was also common. Bilateral CAP aplasia was present in all but one Pug dog at the level of MRI detectable spinal cord lesions. A causal relationship between CAP dysplasia and causes of thoracolumbar myelopathy is speculated but is not confirmed by this study.

Cervical vertebral malformations in 9 dogs: radiological findings, treatment options and outcomes.

BACKGROUND: Disregarding atlantoaxial instability in toy breed dogs associated with dens malformation and cervical spondylomyelopathy; cervical vertebral malformations are rare and poorly characterised in veterinary medicine and consequently treatment strategies and clinical outcome are sparsely documented. RESULTS: Electronic clinical records at our veterinary referral hospital between April 2009 and November 2018 were searched for patients presented with cervical myelopathy secondary to an underlying suspected vertebral malformation/instability. Nine dogs met the inclusion criteria. Two dogs were diagnosed with atlantoaxial pseudoarthrosis, two dogs with a syndrome similar to Klippel-Feil in humans, two dogs with congenital cervical fusion, two dogs with congenital C2-C3 canal stenosis and deficiencies of the dorsal arch of the atlas and laminae of the axis and one with axial rotatory displacement. Tetraparesis, proprioceptive deficits, cervical hyperesthesia and cervical scoliosis were the most common clinical signs. The axis was the most commonly affected vertebrae (8/9 patients). Patients diagnosed with Klippel-Feil-like Syndrome were the younger (average of 262.5 days) and patients diagnosed with fused vertebrae the oldest (average of 2896 days) in our studied population (average of 1580.8 days). CONCLUSION: Cervical vertebral malformations are rare, or alternatively, being underdiagnosed in veterinary medicine. Patients diagnosed with Klippel-Feil-like Syndrome had a successful medium and long-term outcome with conservative management. Surgical treatment was often indicated for the other conditions presented in this study due to spinal instability and/or myelopathy. Stabilisations via ventral approaches were revealed to be safe. Multicentre and prospective studies are necessary in veterinary medicine to better characterise clinical outcomes in cervical vertebral malformations.

MRI characteristics for "phantom" scratching in canine syringomyelia.

BACKGROUND: A classic sign of canine syringomyelia (SM) is scratching towards one shoulder. Using magnetic resonance imaging (MRI) we investigate the spinal cord lesion relating to this phenomenon which has characteristics similar to fictive scratch secondary to spinal cord transection. Medical records were searched for Cavalier King Charles spaniels with a clinical and MRI diagnosis of symptomatic SM associated with Chiari-like malformation (CM). The cohort was divided into SM with phantom scratching (19 dogs) and SM but no phantom scratching (18 dogs). MRI files were anonymised, randomised and viewed in EFILM ™. For each transverse image, the maximum perpendicular dimensions of the syrinx in the dorsal spinal cord quadrants were determined. Visual assessment was made as to whether the syrinx extended to the superficial dorsal horn (SDH). RESULTS: We showed that phantom scratching appears associated with a large dorsolateral syrinx that extends to the SDH in the C3-C6 spinal cord segments (corresponding to C2-C5 vertebrae). Estimated dorsal quadrant syrinx sizes based on the perpendicular diameters were between 2.5 and 9.5 times larger in dogs with phantom scratching, with the largest mean difference p-value being 0.009. CONCLUSION: SM associated phantom scratching appears associated with MRI findings of a large syrinx extending into the mid cervical SDH. We hypothesise that damage in this region might influence the lumbosacral scratching central pattern generator (CPG). If a scratching SM affected dog does not have a large dorsolateral cervical syrinx with SDH involvement then alternative explanations for scratching should be investigated.

Use of Morphometric Mapping to Characterise Symptomatic Chiari-Like Malformation, Secondary Syringomyelia and Associated Brachycephaly in the Cavalier King Charles Spaniel.

OBJECTIVES: To characterise the symptomatic phenotype of Chiari-like malformation (CM), secondary syringomyelia (SM) and brachycephaly in the Cavalier King Charles Spaniel using morphometric measurements on mid-sagittal Magnetic Resonance images (MRI) of the brain and craniocervical junction. METHODS: This retrospective study, based on a previous quantitative analysis in the Griffon Bruxellois (GB), used 24 measurements taken on 130 T1-weighted MRI of hindbrain and cervical region. Associated brachycephaly was estimated using 26 measurements, including rostral forebrain flattening and olfactory lobe rotation, on 72 T2-weighted MRI of the whole brain. Both study cohorts were divided into three groups; Control, CM pain and SM and their morphometries compared with each other. RESULTS: Fourteen significant traits were identified in the hindbrain study and nine traits in the whole brain study, six of which were similar to the GB and suggest a common aetiology. The Control cohort had the most elliptical brain (p = 0.010), least olfactory bulb rotation (p = 0.003) and a protective angle (p = 0.004) compared to the other groups. The CM pain cohort had the greatest rostral forebrain flattening (p = 0.007), shortest basioccipital (p = 0.019), but a greater distance between the atlas and basioccipital (p = 0.002) which was protective for SM. The SM cohort had two conformation anomalies depending on the severity of craniocervical junction incongruities; i) the proximity of the dens (p <0.001) ii) increased airorhynchy with a smaller, more ventrally rotated olfactory bulb (p <0.001). Both generated 'concertina' flexures of the brain and craniocervical junction. CONCLUSION: Morphometric mapping provides a diagnostic tool for quantifying symptomatic CM, secondary SM and their relationship with brachycephaly. It is hypothesized that CM pain is associated with increased brachycephaly and SM can result from different combinations of abnormalities of the forebrain, caudal fossa and craniocervical junction which compromise the neural parenchyma and impede cerebrospinal fluid flow.

Magnetic resonance imaging characteristics in four dogs with central nervous system neosporosis.

Neosporosis is a polysystemic disease that can affect dogs of any age and can cause inflammation of the central nervous system. Antemortem diagnosis can be challenging, as clinical and conventional laboratory test findings are often nonspecific. A previous report described cerebellar lesions in brain MRI studies of seven dogs and proposed that these may be characteristic for central nervous system Neosporosis. The purpose of this retrospective study was to describe MRI characteristics in another group of dogs with confirmed central nervous system neosporosis and compare them with the previous report. The hospital's database was searched for dogs with confirmed central nervous system neosporosis and four observers recorded findings from each dog's MRI studies. A total of four dogs met inclusion criteria. Neurologic examination was indicative of a forebrain and cerebellar lesion in dog 2 and multifocal central nervous system disease in dogs 1, 3, and 4. Magnetic resonance imaging showed mild bilateral and symmetrical cerebellar atrophy in three of four dogs (dogs 2, 3, 4), intramedullary spinal cord changes in two dogs (dogs 3, 4) and a mesencephalic and metencephalic lesion in one dog (dog 2). Multifocal brain lesions were recognized in two dogs (dogs 1, 4) and were present in the thalamus, lentiform nucleus, centrum semiovale, internal capsule, brainstem and cortical gray matter of the frontal, parietal or temporal lobe. Findings indicated that central nervous system neosporosis may be characterized by multifocal MRI lesions as well as cerebellar involvement in dogs.

Venous sinus volume in the caudal cranial fossa in Cavalier King Charles spaniels with syringomyelia.

Syringomyelia (SM) in Cavalier King Charles spaniels (CKCS) has a complex pathophysiology. Recent studies support a relationship between altered venous drainage and cerebrospinal fluid flow dynamics. The aim of this study was to evaluate the relationship between venous sinus and parenchymal volume within the caudal cranial fossa (CCF) in CKCS with SM (n=22) and without SM (n=12) using magnetic resonance venography (MRV). MRI and MRV images were used to obtain volumetric calculations of CCF volume, as well as the percentage of this volume occupied by parenchyma (CCFP%) and venous sinuses (CCFV%). In CKCS with SM, CCFP% was significantly higher (P<0.001), whilst CCFV% was significantly lower (P=0.001) than in CKCS without SM. These results support a role for reduced venous drainage and parenchymal 'overcrowding' of the CCF in the pathophysiology of SM.

Changes over time in craniocerebral morphology and syringomyelia in cavalier King Charles spaniels with Chiari-like malformation.

BACKGROUND: Chiari-like malformation (CM) and syringomyelia is a neurological disease complex with high prevalence in cavalier King Charles spaniels (CKCS). The natural progression of this disease with time has not been described. The objectives of this study were to i) determine if syringomyelia progresses with time ii) determine if features of craniocrebral morphology previously associated with CM are progressive (including caudal cranial fossa volume, caudal cranial fossa parenchymal volume, ventricular dimensions, height of the foramen magnum and degree of cerebellar herniation). A retrospective morphometric analysis was undertaken in 12 CKCS with CM for which repeat magnetic resonance images were available without surgical intervention. RESULTS: The maximal syrinx width, height of the foramen magnum, length of cerebellar herniation and caudal cranial fossa volume increased over time. Ventricular and caudal fossa parenchymal volumes were not significantly different between scans. CONCLUSIONS: The results of this study suggest that syringomyelia progresses with time. Increased caudal cranial fossa volume may be associated with active resorption of the supraoccipital bone, which has previously been found in histology specimens from adult CKCS. We hypothesise that active resorption of the supraoccipital bone occurs due to pressure from the cerebellum. These findings have important implications for our understanding of the pathogenesis and variable natural clinical progression of CM and syringomyelia in CKCS.

Increase in cerebellar volume in Cavalier King Charles Spaniels with Chiari-like malformation and its role in the development of syringomyelia.

Previous research in Cavalier King Charles Spaniels (CKCS) has found that Chiari-like malformation and syringomyelia (CM/SM) are associated with a volume mismatch between the caudal cranial fossa (CCF) and the brain parenchyma contained within. The objectives of this study were to i) compare cerebellar volume in CKCS (a "high risk' group which frequently develops CM/SM), small breed dogs (medium risk--occasionally develop CM/SM), and Labradors (low risk--CM/SM not reported); ii) evaluate a possible association between increased cerebellar volume and CM/SM in CKCS; iii) investigate the relationship between increased cerebellar volume and crowding of the cerebellum in the caudal part of the CCF (i.e. the region of the foramen magnum). Volumes of three-dimensional, magnetic resonance imaging derived models of the CCF and cerebellum were obtained from 75 CKCS, 44 small breed dogs, and 31 Labradors. As SM is thought to be a late onset disease process, two subgroups were formed for comparison: 18 CKCS younger than 2 years with SM (CM/SM group) and 13 CKCS older than 5 years without SM (CM group). Relative cerebellar volume was defined as the volume of the cerebellum divided by the total volume of brain parenchyma. Our results show that the CKCS has a relatively larger cerebellum than small breed dogs and Labradors and provide evidence that increased cerebellar volume in CKCS is associated with crowding of cerebellum in the caudal part of the CCF. In CKCS there is an association between increased cerebellar volume and SM. These findings have implications for the understanding of the pathological mechanisms of CM/SM, and support the hypothesis that it is a multifactorial disease process governed by increased cerebellar volume and failure of the CCF to reach a commensurate size.