The Cavalier King Charles Spaniel is often described as the ideal companion dog: affectionate, gentle, adaptable... This is not incorrect. But behind this image lies a worrying medical reality, widely documented in veterinary literature: the Cavalier King Charles is one of the breeds most affected by syringomyelia, a painful neurological disease closely linked to the cranio-cervical malformation selected in the breed.

Understanding this pathology means understanding how aesthetic selection for cranial morphology can create chronic suffering in an animal (and why screening programs and responsible breeding are so important in this breed).

Parker et al., Veterinary Record, 2011: PubMed 21672954

Understanding Chiari-like malformation and syringomyelia

Chiari-like malformation (CM) is a congenital skull anomaly in which the posterior cranial fossa (the part of the skull housing the cerebellum) is too small to contain the brain. The cerebellar tissue is then compressed and partially protrudes into the spinal canal at the foramen magnum.

This compression disrupts the circulation of cerebrospinal fluid (CSF) around the spinal cord. The disruption of this flow gradually leads to the formation of fluid-filled cavities within the spinal cord itself: this is syringomyelia (SM).

In summary: in the Cavalier King Charles, and for aesthetic reasons, the skull has been bred to be too small for the brain it contains...

Lewis et al. (The Veterinary Journal, 2010) increased the heritability of syringomyelia in Cavalier King Charles to 0.37. Therefore, the disease is also partially passed down from parents.

Prevalence: sobering figures

The prevalence of CM (Chiari-like malformation) and SM (syringomyelia) in the breed is among the highest ever documented for a hereditary neurological pathology in dogs.

Almost all Cavaliers exhibit the malformation on MRI...

Syringomyelia progresses from 25% at 1 year to 70% after 6 years (according to Parker's asymptomatic cohort). Clinical forms affect 15.4% of the breed (Thøfner et al., 2015). MRI-based breeding programs have shown only modest improvement at this stage (Limpens et al., 2024).

Clinical signs: recognizing pain

The most characteristic (and often misinterpreted) sign is "phantom scratching": the dog scratches its neck or shoulder on one side only, without actual skin contact, sometimes only when walking or wearing a collar. This behavior is linked to neuropathic pain generated by the syrinx.

A study by Rusbridge et al. (2019, JVIM) on 130 CKCS showed that behavioral signs such as vocalization, spinal pain, decreased activity, aversion to touch, and altered emotional state are frequent, and some of them may precede obvious neurological deficits.

Management and screening

There is no curative treatment for Chiari malformation. Management is medical (analgesics, gabapentin, carbonic anhydrase inhibitors to reduce CSF production) or surgical (foraminal decompression). Surgery initially improves signs in about 80% of operated dogs, but 47% secondarily deteriorate in the series by Rusbridge et al. (2007), which reminds us that improvement is not always lasting.

The long-term key remains rational genetic selection. Dutch, Belgian, and Danish data suggest that MRI-based screening of breeding animals can lead to positive outcomes, but the effect observed so far remains modest and is highly dependent on the age at screening and breeding choices (Wijnrocx et al., 2017; Limpens et al., 2024).

What you can do

• Before purchase: demand a BVA/KC MRI certificate for both parents, or an equivalent in countries where screening is available. A breeder who does not screen their breeding animals is not taking the health of the breed seriously...

• Use a harness instead of a collar: collars exert cervical pressure that aggravates pain in dogs with SM (syringomyelia). A harness is recommended by all breed specialists.

• Monitor behavior: any repeated unilateral scratching, any spontaneous complaint, any change in behavior (irritability, refusal to be touched on the head or neck) warrants a neurological consultation.

• Do not minimize chronic pain: a Cavalier that seems "normal" may be suffering in silence. Neuropathic pain is difficult to quantify but real. Studies show that symptomatic SM (syringomyelia) dogs have significantly lowered sensitivity thresholds.

• In case of diagnosis: discuss with your veterinarian medical options and long-term prognosis based on the size of the syrinx (a transverse diameter greater than 4 mm is associated with a higher risk of severe signs).

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Sources

1. Parker J.E. et al. (2011). Prevalence of asymptomatic syringomyelia in Cavalier King Charles spaniels. Veterinary Record, 168: 667. PubMed 21672954
2. Lewis T. et al. (2010). Heritability of syringomyelia in Cavalier King Charles spaniels. The Veterinary Journal, 183: 345–347. PubMed 19914109
3. Wijnrocx K. et al. (2017). Twelve years of Chiari-like malformation and syringomyelia scanning in Cavalier King Charles Spaniels in the Netherlands and Belgium. PLoS ONE, 12(9): e0184893. PMCID PMC5608246
4. Ancot F. et al. (2018). A genome-wide association study identifies candidate loci associated to syringomyelia secondary to Chiari-like malformation in CKCS. BMC Genetics, 19: 16. PubMed 29566674
5. Rusbridge C. et al. (2007). Chiari-like malformation with syringomyelia in the CKCS: long-term outcome after surgical management. PubMed 17614920
6. Rusbridge C. et al. (2019). Behavioral and clinical signs of CM-associated pain and syringomyelia in CKCS. JVIM. PubMed 31290195
7. Thøfner M.S. et al. (2015). Prevalence and heritability of symptomatic syringomyelia in Cavalier King Charles Spaniels and long-term outcome in symptomatic and asymptomatic littermates. Journal of Veterinary Internal Medicine. PubMed 25308931
8. Limpens C. et al. (2024). The effect of MRI-based screening and selection on the prevalence of syringomyelia in the Dutch and Danish Cavalier King Charles Spaniels. Frontiers in Veterinary Science. PMCID PMC10859432
9. UFAW — Cavalier King Charles Spaniel: Syringomyelia. ufaw.org.uk