Chiari-like malformation (CLM) and syringomyelia (SM) are serious neurological conditions most common in small-breed dogs — especially Cavalier King Charles Spaniels — where the skull is too small for the brain, causing fluid-filled cavities to form in the spinal cord. The hallmark is neck and shoulder pain, sometimes with "phantom scratching" at the neck.
Last reviewed: June 2026
What Are Chiari-Like Malformation and Syringomyelia?
Chiari-like malformation (CLM) — analogous to Chiari type I malformation in humans — occurs when a dog's skull is disproportionately small relative to its brain, causing the caudal (rear) portion of the cerebellum to be pushed through the foramen magnum (the opening at the base of the skull into the spinal canal). This compression disrupts normal cerebrospinal fluid (CSF) circulation. Over time, turbulent and obstructed CSF flow leads to syringomyelia (SM): the formation of fluid-filled cavities (syringes or syrinxes) within the spinal cord itself. These cavities damage the cord from the inside, causing pain and progressive neurological deficits.
CLM and SM are closely linked — CLM is the cause and SM is often the consequence. As described in Ettinger's Textbook of Veterinary Internal Medicine, Cavalier King Charles Spaniels (CKCS) have an extraordinarily high prevalence: MRI studies suggest more than 70% of adult CKCS have CLM, and a substantial proportion develop SM. Other affected breeds include Brussels Griffons, Chihuahuas, Pugs, Yorkshire Terriers, and other brachycephalic and toy breeds with similar skull conformation.
Signs and Symptoms
CLM without SM may be clinically silent, but SM produces a characteristic and often distressing set of signs:
Most distinctive sign:
- Phantom scratching — the dog scratches at the neck, shoulder, or ear without making contact with the skin; one hind leg scratches the air beside the neck while walking. This is caused by abnormal pain or sensation (dysesthesia) from the syrinx affecting the cervical spinal cord
Other signs of SM and CLM:
- Neck and shoulder pain — whimpering when the collar or leash puts pressure on the neck; reluctance to put the head down to eat or drink
- Scoliosis (spinal curvature), typically curving away from the affected side
- Weakness or incoordination in one or more limbs (ataxia)
- Head tilt or abnormal eye movements (nystagmus) if the brainstem is significantly compressed
- Sensitivity to touch around the head, neck, and ears — some dogs yelp when touched or groomed in these areas
- Sleep disturbance — SM pain often worsens when lying down, causing restlessness at night
Signs of progression:
- Increasing frequency and duration of phantom scratching episodes
- Worsening limb weakness progressing to paresis
- Loss of balance and difficulty navigating stairs
Diagnosis
MRI is the definitive diagnostic tool — it directly visualizes the cerebellar herniation and any syrinx formation within the cervical spinal cord. Plain radiographs and CT can suggest skull conformation but cannot visualize syringes (Rusbridge et al., 2006, JVIM). The MRI protocol typically evaluates the entire cervical spinal cord and foramen magnum region.
A thorough neurological examination documents which deficits are present and helps distinguish CLM/SM from other causes of neck pain (intervertebral disc disease, atlantoaxial instability, meningitis).
Treatment Options
Management depends on the severity of signs and the imaging findings. The goals are pain relief and slowing syrinx progression:
Medical management (mild to moderate cases):
- Gabapentin or pregabalin — first-line for neuropathic pain and dysesthesia from the syrinx
- Omeprazole — reduces CSF production, which can decrease pressure and slow syrinx formation; commonly used in combination
- NSAIDs or steroids — for inflammatory pain component; cannot be combined
- Furosemide — occasionally added to further reduce CSF production
Surgical management (moderate to severe, or progressive cases):
- Foramen magnum decompression — surgery to widen the opening at the base of the skull, relieve cerebellar compression, and restore CSF flow
- Surgery can reduce pain and halt syrinx progression in many dogs, though existing neurological deficits may not fully reverse
- Recurrence of obstruction is possible over time
As described in Tilley's The 5-Minute Veterinary Consult: Canine and Feline, both medical and surgical options provide meaningful improvement for many dogs, though CLM/SM in severely affected breeds is a lifelong condition requiring ongoing management.
When to See a Vet
Call your vet today if:
- Your dog scratches at the neck or ear in the air without touching the skin
- Your dog yelps or cries out when you touch the neck, ears, or collar area
- Your dog seems reluctant to lower its head to eat or drink
- You notice your dog walking with a curved back or stumbling
Go to the ER immediately if:
- Your dog suddenly cannot walk or stand
- Your dog is crying out in pain and cannot be comforted
- You notice rapid worsening of limb weakness over hours
- Your dog collapses and cannot rise
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Frequently Asked Questions
What breeds are most at risk for Chiari malformation and syringomyelia? Cavalier King Charles Spaniels carry the highest documented risk — MRI studies show CLM in over 70% of adult CKCS, with many developing syringomyelia. Other high-risk breeds include Brussels Griffons, Chihuahuas, Pugs, Maltese, Yorkshire Terriers, and Pomeranians. The common factor is brachycephalic skull conformation: a foreshortened skull housing a brain that has little room to expand, predisposing to cerebellar herniation.
Is syringomyelia painful for dogs? Yes — SM is considered one of the more painful neurological conditions in dogs. The fluid-filled cavities within the spinal cord create abnormal sensations (dysesthesia) that manifest as the characteristic phantom scratching and pain behaviors. Neuropathic pain can be severe, disruptive to sleep, and affects quality of life significantly. This is why pain management is central to treatment regardless of whether surgery is pursued.
Can dogs with syringomyelia live a normal life? Many dogs with mild to moderate SM maintain good quality of life with appropriate pain management and monitoring. Severely affected dogs, particularly those with rapid progression or significant limb weakness, face greater challenges. Lifelong medication, regular neurological rechecks, and periodic MRI monitoring are typically needed. Surgery can provide meaningful relief in selected patients but does not cure the underlying skull conformation.
How much does diagnosing and treating CLM/SM cost in dogs? Neurological exam and initial consultation typically run $200–400. MRI (essential for diagnosis) costs $1,500–3,000 at most facilities. Ongoing medical management with gabapentin, omeprazole, and periodic rechecks runs $100–250 per month. Foramen magnum decompression surgery ranges from $3,500–6,000 or more at a neurology specialist center. Post-surgical MRI recheck adds another $1,500–2,500.
How is Chiari-like malformation diagnosed without MRI? It cannot be definitively diagnosed without MRI. Plain skull radiographs and CT can document skull conformation but cannot show cerebellar herniation reliably and cannot detect syrinxes within the spinal cord at all. A dog with classic signs (CKCS breed, phantom scratching, neck pain) may be presumptively treated while MRI is arranged, but treatment decisions are ideally guided by MRI findings.
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