Facial changes related to brachycephaly in Cavalier King Charles Spaniels with Chiari-like malformation associated pain and secondary syringomyelia

Association of Extreme Brachycephaly With Persistent Fontanelles in Adult Chihuahuas

BACKGROUND

Although persistent fontanelles (PFs) are common in adult Chihuahuas, their association with cranial morphology remains unknown.

OBJECTIVES

To identify whether cranial morphology is associated with PFs in Chihuahuas and if bodyweight is associated with cranial morphology in this breed.

ANIMALS

Fifty client-owned Chihuahuas.

METHODS

In this retrospective cross-sectional study using computed tomography images, we measured two different cranial base lengths (1 and 2), cranial length, height, and width, and two craniofacial angles. We calculated the ratios of cranial height to cranial base lengths 1 and 2, cranial height to length, cranial height to width, and cranial width to length (cranial index [CrI]). We evaluated if total PF area and number of cranial sutures affected by PFs were associated with craniometric measurements and their ratios and craniofacial angles. Additionally, we evaluated if the craniometric ratios were associated with bodyweight.

RESULTS

Total PF area was larger and number of cranial sutures affected by PFs higher in dogs with higher cranial height to cranial base length ratios 1 (estimate, [95% confidence interval], p: 2.295, [1.204-4.377], p = 0.01 and 1.720, [1.212-2.442], p = 0.002, respectively) and 2 (1.203, [1.069-1.354], p = 0.003 and 1.087, [1.011-1.169], p = 0.02, respectively) and CrI (1.225, [1.079-1.391], p = 0.002, and 1.134, [1.057-1.215], p < 0.001, respectively). Higher CrI was associated with lower bodyweight (-2.600, [-4.102 to -1.098], p = 0.001).

CONCLUSION AND CLINICAL IMPORTANCE

Our results suggest that in Chihuahuas, lower bodyweight is associated with more extreme brachycephaly and extreme brachycephaly is associated with PFs.

A data driven approach for soft tissue biomarker identification linked to Chiari-like malformation and syringomyelia

Canine Chiari-like malformation (CM) is a neuroanatomical condition associated with conformational change of the cranium, craniocervical junction and neuroparenchyma, resulting in pain (Chiari associated pain or CM-P) and the development of syringomyelia (SM). The associated neuro-disability in affected individuals compromises quality of life. CM is characterized by overcrowding of the brain and cervical spinal cord and is predisposed by skull-base shortening and miniaturization with brachycephalic toy dogs overwhelmingly represented. Magnetic resonance imaging (MRI) is conventionally used for diagnosis; however, CM is complex and ubiquitous in some dog breeds so that diagnosis of CM-P relies on a combination of clinical signs, MRI, and elimination of other causes of pain. This research aimed to identify cranial and spinal pathologies and neural morphologies linked to CM-P and SM in dogs using MRI scans and machine learning with the aim of identifying novel data driven biomarkers which could confirm CM-P and identify dogs at risk of developing SM. The methodology identified four regions of interest as having robust discrimination for CM-P, with 89% sensitivity and 76% specificity. A set of morphological features linked to CM-P were identified. Four regions of interest were also identified as having robust discrimination for SM, with 84% sensitivity and 80% specificity. Overall, these findings shed light on the distinct morphologies related to CM-P and SM, offering the potential for more accurate and objective diagnoses in affected dogs using MRI. These results contribute to the further understanding of the complex pathologies associated with CM and SM in brachycephalic toy pure and mixed breed dogs and support the potential utility of data-driven techniques for advancing our knowledge of these debilitating conditions.

CT-based and manual external skull measurements for Chiari-like malformation and syringomyelia in Pomeranians

Studies in Pomeranians as well as other breeds have looked at clinical signs or external features as predictors of Chiari-like malformation (CM) and syringomyelia (SM). The aim of this study is to describe and analyze morphometric factors of the skull of Pomeranians with and without CM/SM by means of CT as well as manual external measurements. Ninety-two Pomeranians >12 months of age were included that underwent both CT and MRI studies of the head and cervicothoracic vertebral column. Two observers independently reviewed the CT imaging studies and performed quantitative measurements. External measurements were taken from the head of dogs when under general anesthesia using a tape measure and a caliper. Externally measured mandible length was associated with the probability of having SM (p = 0.043). Mandible length was moderately correlated with weight (Pearson correlation coefficient = 0.585, p < 0.001). A cutoff for mandible length of 58 mm yielded a sensitivity of 96% (95% confidence interval 89-100%), meaning dogs in this study population with a mandible length shorter than 58 mm were highly likely to have SM. The measurement of the length of the mandible could help to determine the probability of a Pomeranian having SM, especially when combined with the presence or absence of owner reported clinicals signs as shown in previous studies.

Association among raised intraventricular pressure, clinical signs, and magnetic resonance imaging findings in dogs with congenital internal hydrocephalus

BACKGROUND

Dogs with internal hydrocephalus do not necessarily have high intraventricular pressure (IVP).

HYPOTHESIS/OBJECTIVES

Not all reported MRI findings indicate high IVP and some clinical signs might be associated with elevated IVP and syringomyelia.

ANIMALS

Fifty-three dogs.

MATERIALS AND METHODS

Cross-sectional study. Clinical signs and MRI findings were evaluated for an association of IVP >12 mm Hg and syringomyelia.

RESULTS

High IVP was associated with obtundation OR 4.64 (95% CI 1.27-16.93) (P = .02), head tilt OR 6.42 (95% CI 1.08-37.97) (P = .04) and nystagmus OR 8.24 (95% CI 1.44-47.07) (P = .02). Pain was associated with syringomyelia OR 3.4 (95% CI 0.98-11.78) (P = .05). The number of affected ventricles was associated with high IVP OR 2.85 (95% CI 0.97-8.33) (P = .05) and syringomyelia OR 12.74 (95% CI 2.93-55.4) (P = .0007). Periventricular edema OR 24.46 (95% CI 4.54-131.77), OR 7.61 (95% CI 1.91-30.32) (P < .0002, P = .004) and signal void sign OR 17.34 (95% CI 4.01-74.95), OR 4.18 (95% CI 1.16-15.02) (P < .0001, P = .03) were associated with high IVP and syringomyelia. The probability for syringomyelia is lower with disruption of the internal capsule OR 0.19 (95% CI 0.05-0.72) (P = .01) and higher VBR OR 0.25 (95% CI 0.1-0.63) (P = .004).

CONCLUSIONS AND CLINICAL IMPORTANCE

Previously reported MRI findings are not predictive of high IVP. Clinical signs and MRI findings should be used to make a diagnosis of internal hydrocephalus in dogs with or without high IVP.

Longitudinal assessment of syringomyelia in Pomeranians

Introduction

Chiari-like malformation (CM) and syringomyelia (SM) are disorders that, in dogs, affect mainly small and toy breeds, including the Pomeranian. These disorders are linked to a great number of (owner-reported) clinical signs (ORCS) suggestive of pain. Aging was associated with an increased risk of having SM in several studies. However, there are only a few longitudinal studies that assess the presence and severity of CM/SM over time in CKCS dogs and progression of SM was linked to progression of clinical signs. The aim of this study was to investigate ORCS, CM/SM classification, and quantitative syrinx parameters in relation to progression of time (age) within individual Pomeranians.

Materials and methods

Pomeranians with or without ORCS and with or without diagnoses of CM/SM were included that had undergone two (or more) MRI studies of the craniocervicothoracic region between January 2020 and June 2023. Classification of CM/SM and quantitative syrinx measurements were performed. Absolute values as well as ratios for syrinx height, width, and cross-sectional area were included for analysis.

Results

A total of 19 Pomeranians were included in the study, of which 11 were male (58%) and 8 were female (42%). The median age at the time of MRI1 was 26 months (range 7-44 months). The median scan interval was 26 months (range 11-49 months). Eleven dogs (58%) were presented with ORCS at the time of MRI1, whereas the other 8 dogs (42%) had no ORCS at that time. At the time of MRI2, there were 17/19 dogs (89%) with ORCS and 2/19 dogs without ORCS (11%). Dogs were significantly more likely to have ORCS at MRI2 than MRI1 (p = 0. 0411). There was no significant difference between CM/SM classification at the time of MRI1 and MRI2. Significant differences were found between MRI1 and MRI2 for syrinx height (based on transverse images) (absolute value and ratio P = 0.0059), syrinx width (absolute value P = 0.1055, ratio P = 0.0039), and syrinx cross sectional area (absolute value P = 0.0195, ratio P = 0.0217).

Discussion

There are differences in the presence or absence of ORCS as well as quantitative syrinx measurements in Pomeranians at different ages. This finding supports that longitudinal changes occur in the SM status of Pomeranians.

Clinical predictors of syringomyelia in Cavalier King Charles Spaniels with chiari-like malformation based on owners' observations

BACKGROUND

Syringomyelia (SM) is a prevalent inherited developmental condition in Cavalier King Charles Spaniels (CKCSs) with Chiari-like malformation (CM), accompanied by a variety of clinical manifestations, including signs of neuropathic pain. Magnetic resonance imaging (MRI) is the gold standard in SM diagnosis. However, it is desirable to establish clinical predictors that can identify CKCSs with a large clinical syrinx that needs treatment, as some owners cannot afford or lack access to MRI. The aims of the study were to investigate owner-reported clinical signs of SM and clinical predictors of a large clinical syrinx, using predictive values of significant signs, individually and in combinations. Eighty-nine CKCSs participated in this retrospective study. Based on MRI diagnosis, dogs were distributed into three groups: CM without syrinx or with a maximum transverse width < 2 mm (n = 13), CM with small syrinx 2.00-3.99 mm (n = 26) and CM with large syrinx ≥4 mm (n = 50). A structured investigator-owner interview using a standardized questionnaire was used to collect data regarding clinical signs of CM and SM. The statistical tests Pearson's chi-square, Fisher's Exact and Spearman's rank order were used to assess the difference in owner-reported signs between groups. For signs with significant differences, positive and negative predictive values (PPV and NPV) were calculated.

RESULTS

Following clinical signs were reported significantly more frequent in dogs with a large syrinx: phantom scratching, bilateral scratching of the neck or shoulder, aversion when that area is touched, or exacerbation of clinical signs when the dog is emotionally aroused. Each individual sign had a high PPV, indicative of a large clinical syrinx. The PPV increased further when the signs phantom scratching, aversion to touch to the head, neck or shoulder, and a preferred head posture during sleep were present in combination.

CONCLUSIONS

Specific clinical signs can be used individually and in combination as clinical predictors of a large clinical syrinx in CKCSs with CM and SM. General practitioners can utilize this information to identify CKCSs with a large syrinx to initiate necessary treatment. This is particularly useful in cases where access to or affordability of an MRI diagnosis is limited.

The effect of MRI-based screening and selection on the prevalence of syringomyelia in the Dutch and Danish Cavalier King Charles Spaniels

Introduction

Syringomyelia (SM) is a heritable disorder causing a fluid filled cavity (FFC) in the spinal cord with a reported overall prevalence of 39 to 46% in the Cavalier King Charles Spaniels (CKCS). Breeders started screening their CKCS with MRI in the Netherlands since 2004 and in Denmark since 2015. The goal of this study was to evaluate the effect of MRI-based selection in breeding on the prevalence of SM.

Method

MRI scans of 2,125 purebred CKCS were available. SM was defined as having a visible FFC in the spinal cord. The prevalence of SM per year of birth was calculated, and a logistic regression was used to evaluate the affected status of offspring from affected versus unaffected parents and age category of the parent and study the combined effect of parental status and age-category to evaluate the effect on the affected status of the offspring.

Results

The mean FFC in affected CKCS was 2.03 ± 1.47 mm and ranged from 0.5 to 9 mm (median of 1.5 mm). An age effect exists as older CKCS, which has a higher frequency of being affected compared with younger CKCS. There was no significant sex predilection for SM in this dataset. The mean prevalence of SM decreased slightly from 38% (2010-2014; 2.8 ± 1.3 years of age (mean ± sd); median 2.6 years) to 27% (2015-2019; 2.4 ± 1.2 years of age; median 2.1 years) in the screened population of CKCS (p = 4.3e-07). Breeding with two affected parents increased the odds ratio with 3.08 for producing affected offspring (95% CI 1.58-6.04) compared with breeding with unaffected parents.

Discussion

MRI-based screening and selection against SM led to a minimal decrease in the prevalence of SM in the Dutch and Danish CKCS population. Breeding with dogs with SM significantly increases the risk of affected offspring. As the disorder is progressive with age, and based on the results of this study, MRI-based screening for all CKCS is recommended at an age of 3 years or older, and to reduce SM more effectively, CKCS affected with SM should not be used for breeding.

Phenotypic characterization of Pomeranians with or without Chiari-like malformation and syringomyelia

Introduction

Chiari-like malformation (CM) and syringomyelia (SM) are frequently diagnosed conditions in small and toy dog breeds, such as the Cavalier King Charles Spaniel and Griffon Bruxellois. CM/SM is only rarely reported in Pomeranians in literature to date. The aims of this study are to 1/describe the phenotype of Pomeranians with or without CM/SM and 2/evaluate for differences and associations between CM/SM and owner-reported clinical signs (ORCS) or signalment factors.

Materials and methods

From February 2015 to June 2023, historical data and signalment (including country of origin, pedigree, sex and neuter status, age, and body weight) and ORCS of Pomeranians were recorded at multiple institutions. MRI studies of all dogs were evaluated for classification of CM/SM. Additionally, quantitative measurements were performed for SM.

Results

A total of 796 dogs from 22 different countries were included. Total prevalence of CM was 54.9% (437/796) and the prevalence of SM was 23.9% (190/796). The top 5 ORCS included 1/scratching with skin contact, rubbing head or ears, or both (57.6% of dogs with ORCS), 2/air licking (30.7% of dogs with ORCS), 3/spontaneous signs of pain (26.0% of dogs with ORCS), 4/persistent licking front and/or hind paws (22.6% of dogs with ORCS), 5/phantom scratching (22.6% of dogs with ORCS). Phantom scratching, vocalization, head shaking, spontaneous signs of pain, and air licking were associated with having SM. There were no statistically significant associations between quantitative syrinx measurements and ORCS. There were statistically significant associations between CM classification and 1/country of origin, 2/having a pedigree, and 3/age. There were statistically significant associations between SM classification and 1/age and 2/body weight.

Discussion

This is the first large study evaluating CM/SM in the Pomeranian dog breed. Veterinary clinicians can use these findings to increase the likelihood of correctly determining the presence or absence of CM/SM in Pomeranians. Breeders may consider using the information regarding signalment factors as well as ORCS associated with CM/SM classifications to select dogs for screening procedures. But an MRI-based diagnosis is needed to properly ascertain the exact CM/SM status of their breeding stock until a fool-proof characteristic or genetic marker is found.

Biopsy and histologic findings of the dura mater at the level of the foramen magnum in 121 CKCS with Chiari-like malformation

To describe histopathologic features found in dural biopsies of Cavalier King Charles Spaniels (CKCS) with Chiari-like malformation (CM) and identify any associations between age, duration of clinical signs, syrinx location or syringomyelia (SM, and quality of life (QOL). The medical records of 121 consecutive client owned CKCS with CM and SM, confirmed by whole body magnetic resonance imaging (MRI), that underwent foramen magnum decompression (FMD) with cranioplasty and durectomy with biopsy from 2006 to 2016 were retrospectively reviewed. Dural biopsies were submitted to a board-certified veterinary pathologist for histopathologic interpretation. The chi-square test was used to analyze associations between histologic findings and categorical variables. For continuous measures, the Kruskal–Wallis non-parametric test was used to compare distributions across pathology categories. A result was considered statistically significant at the p < 0.05 level of significance. The mean age, duration of pre-surgical clinical signs, and pre-operative QOL (1–5 scale) were 44.27 months, 44.78 weeks, and 2.72, respectively. Syringomyelia was found in the cervical region only in 39 of 121 (32.23%) of dogs, in the cervical and thoracic region only in 17 of 121 (14.05%) of dogs, and in the cervical, thoracic, and lumbar region combined in 65 of 121 (53.72%) of dogs. Sixty-six of one hundred twenty-one (54.55%) dural biopsy specimens had histopathology changes; fifty-five (45.45%) did not. Forty-three of one hundred twenty-one (35.54%) dural biopsy specimens had osseous metaplasia, 16 of 121 (13.22%) had evidence of fibrosis, 4 of 121 (3.31%) had arachnoid hyperplasia, and 3 of 121 (2.48%) had evidence of mineralization. Most dogs with CM were found to have histopathologic changes in the dura at the time of FMD cranioplasty was performed. These dural changes can be observed in dogs experiencing clinical signs for a time period as short as 4 weeks prior to presentation. The histopathologic changes were not associated with age, breed, duration of clinical signs, the location of syringomyelia or QOL. The influence of histopathologic changes on long-term prognosis in dogs without dural decompression is unknown since all dogs in this study had dural resection.

Epidemiology of periodontal disease in dogs in the UK primary-care veterinary setting

Objectives

Periodontal disease is a frequent diagnosis of dogs and can have severe negative impacts on welfare. It was hypothesised that breeds with skull shapes that differ most in conformation from the moderate mesocephalic skull shape have higher odds of periodontal disease.

Materials and Methods

The cohort study included a random sample of dogs under primary veterinary care in 2016 from the VetCompass Programme database. Risk factor analysis used random effects multivariable logistic regression modelling.

Results

The study included a random sample of 22,333 dogs. The 1‐year period prevalence for diagnosis with periodontal disease was 12.52% (95% CI: 12.09 to 12.97). Eighteen breeds showed increased odds compared with crossbred dogs. Breeds with the highest odds included Toy Poodle (odds ratio 3.97, 95% confidence intervals 2.21 to 7.13), King Charles Spaniel (odds ratio 2.63, 95% confidence interval 1.50 to 4.61), Greyhound (odds ratio 2.58, 95% confidence interval 1.75 to 3.80) and Cavalier King Charles Spaniel (odds ratio 2.39, 95% confidence interval 1.85 to 3.09). Four breeds showed reduced odds compared with crossbreds. Brachycephalic breeds had 1.25 times the odds (95% confidence interval 1.11 to 1.42) of periodontal disease compared with mesocephalic breeds. Spaniel types had 1.63 times the odds (95% confidence interval 1.42 to 1.87) compared with non‐spaniel types. Increasing adult bodyweight was associated with progressively decreasing odds of periodontal disease.

Clinical Significance

The high prevalence identified in this study highlights periodontal disease as a priority welfare concern for predisposed breeds. Veterinarians can use this information to promote improved dental care in predisposed dogs, especially as these dogs age.

The Need for Head Space: Brachycephaly and Cerebrospinal Fluid Disorders

Brachycephalic dogs remain popular, despite the knowledge that this head conformation is associated with health problems, including airway compromise, ocular disorders, neurological disease, and other co-morbidities. There is increasing evidence that brachycephaly disrupts cerebrospinal fluid movement and absorption, predisposing ventriculomegaly, hydrocephalus, quadrigeminal cistern expansion, Chiari-like malformation, and syringomyelia. In this review, we focus on cerebrospinal fluid physiology and how this is impacted by brachycephaly, airorhynchy, and associated craniosynostosis.

Facial changes related to brachycephaly in Cavalier King Charles Spaniels with Chiari-like malformation associated pain and secondary syringomyelia

BACKGROUND

Recent studies including an innovative machine learning technique indicated Chiari-like malformation (CM) is influenced by brachycephalic features.

OBJECTIVES

Morphometric analysis of facial anatomy and dysmorphia in CM-associated pain (CM-P) and syringomyelia (SM) in the Cavalier King Charles Spaniel (CKCS).

ANIMALS

Sixty-six client-owned CKCS.

METHODS

Retrospective study of anonymized T2W sagittal magnetic resonance imaging of 3 clinical groups: (1) 11 without central canal dilation (ccd) or SM (CM-N), (2) 15 with CM-P with no SM or <2 mm ccd (CM-P), and (3) 40 with syrinx width ≥4 mm (SM-S). Morphometric analysis assessed rostral skull flattening and position of the hard and soft palate relative to the cranial base in each clinical group and compared CKCS with and without SM-S.

RESULTS

Sixteen of 28 measured variables were associated to SM-S compared to CM-N and CM-P. Of these 6 were common to both groups. Predictive variables determined by discriminant analysis were (1) the ratio of cranial height with cranial length (P < .001 between SM-S and CM-N) and (2) the distance between the cerebrum and the frontal bone (P < .001 between SM-S and CM-P). CM-P had the lowest mean height of the maxillary area.

CONCLUSIONS AND CLINICAL IMPORTANCE

CKCS with CM-P and SM-S have cranial brachycephaly with osseous insufficiency in the skull with rostral flattening and increased proximity of the hard and soft palate to the cranial base. Changes are greatest with CM-P. These findings have relevance for understanding disease pathogenesis and for selection of head conformation for breeding purposes.