Abstract
BackgroundUnderstanding the pathogenesis of the chiari-like malformation in the Cavalier King Charles Spaniel (CKCS) is incomplete, and current hypotheses do not fully explain the development of syringomyelia (SM) in the spinal cords of affected dogs. This study investigates an unconventional pathogenetic theory for the development of cerebrospinal fluid (CSF) pressure waves in the subarachnoid space in CKCS with SM, by analogy with human diseases. In children with achondroplasia the shortening of the skull base can lead to a narrowing of the jugular foramina (JF) between the cranial base synchondroses. This in turn has been reported to cause a congestion of the major venous outflow tracts of the skull and consequently to an increase in the intracranial pressure (ICP). Amongst brachycephalic dog breeds the CKCS has been identified as having an extremely short and wide braincase. A stenosis of the JF and a consequential vascular compromise in this opening could contribute to venous hypertension, raising ICP and causing CSF jets in the spinal subarachnoid space of the CKCS. In this study, JF volumes in CKCSs with and without SM were compared to assess a possible role of this pathologic mechanism in the development of SM in this breed.ResultsComputed tomography (CT) scans of 40 CKCSs > 4 years of age were used to create three-dimensional (3D) models of the skull and the JF. Weight matched groups (7–10 kg) of 20 CKCSs with SM and 20 CKCSs without SM were compared. CKCSs without SM presented significantly larger JF -volumes (median left JF: 0.0633 cm3; median right JF: 0.0703 cm3; p < 0.0001) when compared with CKCSs with SM (median left JF: 0.0382 cm3; median right JF: 0.0434 cm3; p < 0.0001). There was no significant difference between the left and right JF within each group. Bland-Altman analysis revealed excellent reproducibility of all volume measurements.ConclusionA stenosis of the JF and consecutive venous congestion may explain the aetiology of CSF pressure waves in the subarachnoid space, independent of cerebellar herniation, as an additional pathogenetic factor for the development of SM in this breed.
Highlights
Understanding the pathogenesis of the chiari-like malformation in the Cavalier King Charles Spaniel (CKCS) is incomplete, and current hypotheses do not fully explain the development of syringomyelia (SM) in the spinal cords of affected dogs
As only brachycephalic breeds seem to suffer from chiari-like malformation (CLM) [12], it would seem reasonable that the pathophysiological factors leading to this disease could somehow be associated with this severe brachycephaly, as has already been suggested for the Griffon Bruxellois [13]
A stenosis of the jugular foramina (JF) and a consecutive vascular compromise in this opening could contribute to venous hypertension, raised intraventricular and intracranial pressure, and significant cerebrospinal fluid (CSF) jets within the skull of the CKC too
Summary
Understanding the pathogenesis of the chiari-like malformation in the Cavalier King Charles Spaniel (CKCS) is incomplete, and current hypotheses do not fully explain the development of syringomyelia (SM) in the spinal cords of affected dogs. The synchondrosis sphenooccipitalis and sphenopresphenoidalis (or intersphenoidalis) have been assumed to undergo a premature closure in brachycephalic dogs [15], as in humans suffering from achondroplasia [16] In both disease entities enchondral ossification and growth are impaired in extremity- as well as skull base bones [15,16]. A stenosis of the JF and a consecutive vascular compromise in this opening could contribute to venous hypertension, raised intraventricular and intracranial pressure, and significant CSF jets within the skull of the CKC too. The aim of this study was to compare the volumes of the JF in CKCSs affected with SM and CKCSs without SM in order to identify possible factors for the development of SM unrelated to cerebellar herniation
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