Chiari-Like Malformation and Syringomyelia in Canine Breeds

Chiari-like malformation (CM) and secondary syringomyelia (SM) constitute a complex of developmental disorders affecting the skull, brain and spinal cord in predisposed canine breeds, notably brachycephalic toy dogs such as Cavalier King Charles Spaniels. CM arises from under-development of the caudal cranial fossa and craniocervical junction incongruities, leading to cerebellar herniation through the foramen magnum. This distortion impedes normal cerebrospinal fluid (CSF) circulation and can provoke fluid-filled cavities (syrinxes) within the spinal cord, manifesting as neuropathic pain, phantom scratching and motor dysfunction. Recent morphometric and imaging studies have delineated characteristic skull base angulations, alterations in cranial vault height and parenchymal displacement that correlate with clinical severity. Genetic predisposition, breed-specific osteological traits and the degree of brachycephaly interplay in a multifactorial aetiology. Advances in magnetic resonance imaging and three-dimensional morphometric mapping have refined diagnostic criteria, informed breeding guidelines and underpinned emerging surgical and medical interventions aimed at restoring CSF pathways, alleviating pain and preventing syrinx progression. The condition not only poses a welfare concern for affected dogs but also offers comparative insights relevant to human Chiari malformations.

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Chiari-Like Malformation and Syringomyelia in Canine Breeds publication trend

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Technical terms

Chiari-like malformation (CM): Developmental disorder of the posterior skull and cerebellum causing herniation through the foramen magnum and CSF flow obstruction.

Syringomyelia (SM): Formation of fluid-filled cavities (syrinxes) within the spinal cord parenchyma secondary to altered CSF dynamics.

Brachycephaly: Skull conformation characterised by a shortened rostrocaudal length, often associated with craniosynostosis and CSF circulation disturbance.

Caudal cranial fossa: The posterior compartment of the cranial vault housing the cerebellum and brainstem, crucial for normal CSF passage.

Craniocervical junction: Anatomical region where the skull base integrates with the first cervical vertebrae, a site prone to morphological incongruities in CM/SM.

Syrinx: A fluid-filled cavity within the spinal cord parenchyma, central to the pathology of syringomyelia.

References

1. Morphogenesis of Canine Chiari Malformation and Secondary Syringomyelia: Disorders of Cerebrospinal Fluid Circulation. Frontiers in Veterinary Science (2018).
2. The Need for Head Space: Brachycephaly and Cerebrospinal Fluid Disorders. Life (2021).
3. Morphometric features of the craniocervical junction region in dogs with suspected Chiari-like malformation determined by combined use of magnetic resonance imaging and computed tomography.. American Journal of Veterinary Research (2012).
4. Use of Morphometric Mapping to Characterise Symptomatic Chiari-Like Malformation, Secondary Syringomyelia and Associated Brachycephaly in the Cavalier King Charles Spaniel. PLOS ONE (2017).
5. MRI characteristics for “phantom” scratching in canine syringomyelia. BMC Veterinary Research (2017).
6. Using machine learning to understand neuromorphological change and image‐based biomarker identification in Cavalier King Charles Spaniels with Chiari‐like malformation‐associated pain and syringomyelia. Journal of Veterinary Internal Medicine (2019).