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

The Effectiveness of Amitriptyline and Gabapentin in Treating Pomeranians with Chiari-like Malformation and/or Syringomyelia

BACKGROUND

Chiari-like malformation (CM) and syringomyelia (SM) are commonly observed disorders in the Pomeranians. Both disorders can lead to pain and diminish quality of life to varying extents. In veterinary medicine, affected dogs are often treated with gabapentin or pregabalin, which contrasts with human medicine, where the tricyclic antidepressants amitriptyline and nortriptyline are the first-choice treatments.

METHODS

affected dogs were treated with either amitriptyline or gabapentin. If a pre-syrinx was present, furosemide was also added. Owners were asked to score the clinical signs they observed (ORCS).

RESULTS

90 Pomeranians were included, of which 62 received amitriptyline and 28 received gabapentin. Adding furosemide did not have an influence on the outcome. A logistic regression analysis with the number of ORCS, duration of ORCS, treatment (amitriptyline or gabapentin), and outcome (responder or non-responder) as the dependent variable revealed that the number of ORCS had an Odds of 1123 (p = 0.03). Duration of the ORCS (Odds 1.027; p = 0.45) and treatment group had a low influence (Odds 1.258; p = 0.65).

CONCLUSIONS

In this study, amitriptyline demonstrated a moderate, though not statistically significant, more favorable effect on CM/SM pain compared to gabapentin. Adding furosemide to either of these two treatments did not influence the outcome. The outcome for dogs affected by CM/SM is not influenced by MRI grading; however, the number of ORCS and a longer duration negatively impact the outcome. A dose of 1 to 2 mg/kg body weight of amitriptyline administered twice daily proved to be more effective in several dogs.

CT- and MRI-based volumetry for Chiari-like malformation and syringomyelia in Pomeranians

Introduction

Volumetric studies in relation to CM/SM have not been reported in Pomeranians. In this study, we aim to (1) report the intermodality agreement between CT- and MRI-based volumetric measurements of the skull and cervical spinal canal, and (2) assess for differences and associations between the volumetric measurements and CM/SM status.

Methods

Pomeranians were included that underwent CT and MRI studies during the period of February 2022-June 2024. Frontal sinus volume (FSV), caudal cranial fossa volume (CCFV), rostral and middle cranial fossa volume (RMCFV), caudal cranial fossa parenchymal volume (CCFPV), rostral and middle cranial fossa parenchymal volume (RMCFPV), cerebellar parenchymal volume (CPV), brain stem parenchymal volume (BSPV), ventricular system volume (VSV), and spinal canal volume between C1-C7 (CSCV) were measured. CCFV to RMCFV volume index (VI) and CCFPV to CCFV (CCFPV%) were calculated. Agreement between MRI- and CT-based quantitative measurements was assessed with intraclass correlation coefficients. Inferential statistical tests including logistic regression modeling were performed to assess for associations between variables and CM/SM status.

Results

For all volumetric assessments that were performed on both CT and MRI, agreement was good or excellent. There were significant differences between SM normal and abnormal dogs for body weight as well as all volumetric parameters except for CCFPV% and RMCFV. Multiple logistic regression showed that a smaller CCFV and larger VSV were associated with SM.

Conclusion

Smaller CCFV and larger VSV are associated with the development of SM in Pomeranians and have increased odds of SM.

Holocord syringomyelia in 18 dogs

Holocord syringomyelia (HSM) is characterized by a continuous spinal cord cavitation along its entire length and is currently poorly documented in dogs. This retrospective multicentric case series investigates the clinical and MRI findings in 18 dogs with HSM. The median age at presentation was 82 months (range 9-108 months) and French Bulldogs were overrepresented (50%). Signs of myelopathy attributed to HSM were detected in 12 dogs (67%), spinal pain/paresthesia/allodynia in eight (44%), and four dogs (22%) had no HSM-associated signs. The most common neuroanatomical localization was C1-C5 spinal cord segments. On MRI, the cranial limit of HSM was at C1 vertebra in seven (39%) and at C2 in 11 dogs (61%). The caudal limit extended to L3 in four dogs (22%), L4 or L5 in six dogs (33%) each, and L6 in two dogs (11%). The conus medullaris terminated at L5 in one dog (6%), L6 in 11 (61%), and L7 in six dogs (33%). Seventeen dogs (94%) exhibited MRI features of Chiari-like and/or other intracranial/cranio-cervical junction malformations. One dog (6%) was treated surgically, 11 (61%) medically, and six (33%) received no treatment. Over a median follow-up of 12 months (range 2-65 months) in 16 dogs, one dog (6%) improved, nine (56%) deteriorated, four (25%) were static, and two (13%) remained free of HSM-associated signs. This is the first study to describe canine HSM, highlighting a possible breed predisposition in French Bulldogs. The frequent occurrence of myelopathy and disease progression underscores the need for further research into the underlying etiopathogenesis, natural disease evolution, and response to therapeutic interventions.

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.

Craniocervical Morphometry in Pomeranians-Part II: Associations with Chiari-like Malformation and Syringomyelia

BACKGROUND

The aim of Part II of this two-part study is to describe and analyze the association of various aspects and measurements related to the morphometry of the skull and craniocervical region to CM/SM status of Pomeranians, by means of computed tomography (CT) and magnetic resonance imaging (MRI).

METHODS

Prospectively, Pomeranians were included that underwent both CT and MRI studies of the head and cervicothoracic vertebral column. For those cases where qualitative classifications differed between observers, the experienced observer re-evaluated the studies and decided on a final classification that was used for further analysis. For quantitative measurements, the means of the observers' measurements were used for analysis.

RESULTS

Among statistically significant differences in measurements, we found that dogs with SM had a significantly shorter clivus length based on both MRI (p = 0.01) and CT measurements (p = 0.01), and a significantly smaller caudal cranial fossa area based on both MRI (p = 0.02) and CT measurements (p = 0.02).

CONCLUSIONS

Significant morphometrical differences were identified between dogs with or without CM/SM. The findings in this study add to those already described in other breeds and provide further insight into factors that may play a role in the pathogenesis of CM/SM in Pomeranians.

Craniocervical Morphometry in Pomeranians-Part I: Intra-Observer, Interobserver, and Intermodality (CT vs. MRI) Agreement

BACKGROUND

Currently, there are no diagnostic imaging-based studies that have focused specifically on the craniocervical morphology of Pomeranian dogs in relation to Chiari-like malformation and syringomyelia (CM/SM). The aims of Part I of this two-part study are to assess the intra-observer, interobserver, and intermodality reliability and agreement for various aspects of the craniocervical morphology of Pomeranians with and without CM/SM.

METHODS

Prospectively, Pomeranians were included that underwent both CT and MRI studies of the head and cervicothoracic vertebral column. Two observers (experienced and novice) independently performed CM and SM classifications, qualitative assessments, and quantitative measurements. The experienced observer performed these assessments twice. A third observer (experienced) performed CM and SM normal or abnormal classifications.

RESULTS

Ninety-nine (99) dogs were included. Interobserver reliability was influenced by observer experience level. For the experienced versus novice observers, substantial interobserver agreement was found for classification of SM as normal or abnormal (Cohen's kappa = 0.63), while interobserver agreement was fair for classification of SM as normal or abnormal (Cohen's kappa = 0.31). Interobserver, intra-observer, and intermodality reliability were variable for different measurements and assessments, and best overall for the CT-based measurements.

CONCLUSIONS

Interobserver reliability and agreement results should be taken into account in the evaluation of results of future studies as well as the evaluation of imaging studies of Pomeranians presented clinically.

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.

'We have 'Tinder' tools to solve the health issues caused by pedigree dog breeding'

Technology and estimated breeding values are the key to breeding dogs that will live long and have desired behaviour and good health and welfare, argue Aashild Roaldset and Eva Breuer Hustoft.

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.