Intermittent Pain & Scratching in a Cavalier King Charles Spaniel
Kwiatkowska M. A preliminary study. Bull Vet Inst Pulawy , 55 , Pomianowski A. Bull Vet Inst Pulawy , 56, Rusbridge C. J Vet Intern Med , 20 , Vet Surg , 36 , Med Weter , 66 , Export Citation. User Account Log in Register Help. Search Close Advanced Search Help. My Content 1 Recently viewed 1 Syringomyelia and Chia Show Summary Details.
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Syringomyelia: current concepts in pathogenesis, diagnosis, and treatment.
Online ISSN See all formats and pricing Online. Correlations were tested with the Pearson r correlation test. Linear regression was used to model the relationship between variables and ANCOVA was used to determine if the slopes of fitted linear regression models differed significantly. A list of dog breeds in the SB group can be found in Table 2. SB CM Pearson r correlation between Age vs.
The volume of the cerebellum is expressed as a percentage of the total brain volume Cerebellar Brain Percentage. Fitted linear regression lines are also displayed. Furthermore, the degree of cerebellar crowding in the caudal CCF is correlated with increased volume of the cerebellum in CKCS and this is not seen in small breed dogs or Labradors.
The presumed pathological mechanism underlying the association between CM and SM is that the development of SM is mediated by abnormal CSF flow dynamics at the cervicomedullary junction  , . This has been attributed to high-velocity jets of CSF caused by obstruction of the foramen magnum by the herniated portion of the cerebellum and overcrowded brain parenchyma in the caudal occipital region  which is hypothesised to set up a hydrostatic pressure differential between the spinal cord and subarachnoid space and results in the accumulation of perivascular fluid which eventually forms a syrinx .
The degree of crowding may determine the degree of foramen magnum obstruction, and in turn the tendency for syrinxes to form. Cerebellar volume is potentially a key factor in determining the degree of obstruction and interference in normal CSF flow through the foramen magnum, which disposes dogs to the subsequent development of SM. CM in CKCS is the manifestation of cerebellar herniation through the foramen magnum, and previous studies have shown that this is associated with increased crowding of brain parenchyma within the CCF  , .
Computer simulation of syringomyelia in dogs
In our study we tested the hypothesis that this crowding was due to increased cerebellar volume. Our results show that in CKCS the Cerebellum is more crowded in the caudal CCF than in small breed dogs and Labradors, supporting the theory that CM is due to descent and herniation of the cerebellum through the foramen magnum. CKCS had a relatively larger Cerebellar volume and a similar brainstem volume when compared to small breed dogs and Labradors, supporting hypothesis i that CKCS have increased cerebellar volume compared to other breeds of dog.
Our results support hypothesis iii which states that in CKCS an increase in relative cerebellar volume is correlated with an increase in cerebellar crowding in the caudal CCF. It should be noted that small breed dogs and Labradors do not show the same relationship. We infer from this result that during cranial development in Labradors and small breed dogs, a compensatory mechanism maintains the relationship between cerebellar volume and CCF dimensions, and this mechanism is defective in CKCS.
We also found in CKCS that cerebellar crowding in the caudal CCF is more sensitive to changes in relative cerebellar volume than cerebellar crowding in the rostral CCF, which is consistent with the theory that increased cerebellar volume results in the cerebellum shifting caudally and causes obliteration of dead space in the caudal CCF. This also causes herniation of the cerebellum through the foramen magnum i. Unlike humans, we found that CKCS do not appear to have age-related atrophy as there was no correlation between relative cerebellar volume and age.
This supports hypothesis ii , that increased cerebellar volume in CKCS is associated with syringomyelia. The cerebellum to brain volume ratio is consistent between normal dogs and has been shown to decrease with cerebellar degenerative disorders  , but it has never been shown to be increased in size in a canine neurological disorder.
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To the authors' knowledge, no studies have examined the role of cerebellar volume in human Chiari malformation I and associated SM. Generalised overgrowth of brain parenchyma megalencephaly is recognised in over human syndromes  and in some of these conditions posterior cranial fossa overcrowding and herniation of the cerebellum have been reported. These include Macrocephaly—Capillary Malformation, also known as macrocephaly-cutis marmorata telangiectatica congenital  ,  , the closely related megalencephaly polymicrogyria-polydactyly hydrocephalus MPPH syndrome  , Rasopathies  , Alexander's disease  and Lhermitte-Duclos disease .
Megalencephaly is suggestive of disorders of generalized neuro- and gliogenesis. Some of these conditions are also manifested in different parts of the body, such as Macrocephaly—Capillary Malformation, a poorly understood syndrome which is characterized by malformed capillaries and prenatal somatic overgrowth with numerous asymmetries  , . Affected individuals have multiple defects including progressive brain overgrowth which is caused by proliferation of cortical progenitor cells and premature gliogenesis.
A number of Rasopathies which can result in cerebellar herniation include Costello's syndrome  , Neurofibromatosis type 1  , Noonan's syndrome  and cardio-facio-cutaneous syndrome CFC . Generalised megalencephaly in the CKCS is not supported by our findings which indicate that there is enlargement of the cerebellum relative to overall brain volume.
However, there are only a few rare syndromes of cerebellar overgrowth in humans which do not involve generalised brain overgrowth. Diffuse cerebellar enlargement macrocerebellum is a poorly defined syndrome proposed to be related to the response of the cerebellum to an over-expression of growth factors to augment slow cerebral growth . Primary defects of the cerebellum include Lhermitte-Duclos disease  , in which a slow-growing harmatoma causes diffuse hypertrophy of the cerebellar stratum granulosum.
Chiari Malformation II in humans, although associated with reduced posterior cranial fossa volume, is thought to be neuroectodermal in origin and involves enlargement of the anterior lobes of the cerebellum  , . Scope for further research would involve histological and embryological studies of the forebrain and cerebellum to evaluate possible developmental disorders.
It has been proposed that the volume mismatch between the CCF and brain parenchyma in CKCS can be explained by impaired occipital bone development and the consequent reduction in CCF volume  ,  , . In this study, we find that in CKCS, unlike small breed dogs or Labradors, there is a positive correlation between the volume of the cerebellum and degree of crowding in the caudal CCF, which suggests that CM may be due to CCF development not keeping pace with growth of the cerebellum.
Although the occipital bone comprises a single bony plate in an adult individual, its development is complex and mosaic as it develops from the basioccipital, exoccipital, and supraoccipital bones which are derived from distinct acrochordal and parachordal, occipital arch, and supraoccipital cartilages, respectively . Impaired CCF development may be caused by a failure of communication between one or more of these progenitors and the developing neural tube specifically, rhombomere 1, which gives rise to the cerebellum  , .
Alternatively, it could simply be explained by premature closure of growth plates between the bones of the CCF, as has been reported in humans . It has been found that pre-natal posterior cranial fossa development in humans is independent of cerebellar volume but closely parallels the development of the supratentorial bony compartment . If this is also true in dogs it may have implications for the development of CM, as the CCF may have a restricted capacity to adapt to the volume of an enlarged cerebellum through expansion of the sutures between the occipital bones and their neighbours.
Studies of human skulls have found that the occipital bones adapt to the shape of the growing cerebellum.
In one study, the occipital bones showed a resorbtive pattern of bone around the cerebellar hemispheres in adults and in children  , suggesting that bone remodelling continues long after skull sutures have fused. It has also been noted on post-mortem examination of CKCS and other small breed dogs that the supraoccipital bone overlying the cerebellar vermis is remarkably thin and sometimes eroded so that the foramen magnum is enlarged dorsally  , which could indicate that there has been substantial bone resorbtion.
Work is needed to elucidate the mechanisms of occipital growth in dogs to determine the extent to which an osteo-resorbtive process can mitigate an enlarged cerebellum in CKCS and in other breeds. Histopathological studies of occipital bone development are needed in order to compare the CKCS to other breeds of dog.
The possibility of a cerebellar growth disorder also deserves scrutiny. In order to assess the clinical significance of cerebellar volume and CCF volume as prognostic indicators, further cohort and longitudinal studies are needed. In human medicine, investigation of the role of increased cerebellar volume in the development of Chiari malformation I and associated SM may be warranted. We would like to acknowledge the owners of the patients who participated in this study and the veterinarians who referred them to us. We also would like to acknowledge Hannah Cross for establishing our method, our clinical investigation centre for their technical support and our clinical team, especially the radiographers Lindsey Butler, Victoria Watts and Katie Hellier for their technical assistance with the MR imaging.
Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Introduction Chiari-like Malformation CM and syringomyelia SM is a debilitating and painful disease complex in the Cavalier King Charles Spaniel dog breed CKCS which is regarded as a complex oligogenic trait of moderately high heritability  ,  ,  , . Aims of study These previous studies did not identify which of the sub-divisions of the hindbrain, if any, were enlarged in CKCS with syringomyelia.
Our hypotheses are: cerebellar volume is larger in CKCS than in other breed groups. We further hypothesise that: Increased cerebellar volume in CKCS is correlated with increased crowding of the cerebellum in the caudal part of the CCF. Breeds were selected according to the same criteria as a previous volumetric study on these groups  : CKCS, Labrador or a small breed from the toy or utility groups as defined by the Kennel Club; all skeletally mature over 8 months of age in CKCS and SB, over 12 months of age in Labradors.
Dogs with parenchymal space-occupying lesions or other conditions thought likely to raise intracranial pressure were excluded. Midsagittal scans had to have included the first three vertebrae of the cervical spine.go here
Syringomyelia: current concepts in pathogenesis, diagnosis, and treatment
CM was defined as evidence of caudal cerebellar herniation into the foramen magnum or indentation by the supraoccipital bone, irrespective of the presence of SM . A syrinx was defined as a fluid-containing cavity within the spinal cord parenchyma with a transverse diameter of greater than or equal to 2 mm . MR image analysis The MR imaging report of a board-certified radiologist was consulted for each patient.
Figure 2. Partitioning of the CCF and cerebellum mid-saggital view. Table 2. Figure 4.
Cerebellar crowding within different parts of the caudal cranial fossa comparing Labradors, small breed dogs and Cavalier King Charles Spaniels. Figure 5. Cerebellar crowding within different parts of the caudal cranial fossa comparing different groups of Cavalier King Charles Spaniels. Figure 6.