What are the clinical signs and management options for Chiari-like malformation and syringomyelia in dogs?

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Chiari-like malformation (CM) and syringomyelia (SM) in dogs present primarily as neuropathic pain, with phantom scratching, vocalization, and signs of myelopathy emerging as disease progresses — and MRI is the diagnostic gold standard, though specific clinical sign combinations can predict syrinx severity when imaging is unavailable. --- Clinical Signs Pain is the dominant and most common clinical sign of CM/SM, manifesting as vocalization (65.4%), spinal pain (54.6%), reduced activity (37.7%), reduced ability to navigate stairs or jump (35.4%), touch aversion (30.0%), altered emotional state (28.5%), and sleep disturbance (22%).8 Crying out when lifted is the most commonly owner-reported pain sign.12 Head scratching or rubbing occurs in 28.5% of affected Cavalier King Charles Spaniels (CKCS) and is inversely associated with syrinx size — it is less common as the syrinx enlarges.8 Phantom scratching, scoliosis, weakness, and postural deficits are restricted to dogs with a maximum transverse syrinx diameter ≥4 mm and are not seen with smaller syringes.8 In Pomeranians, the top owner-reported signs are scratching with skin contact or head/ear rubbing (57.6%), air licking (30.7%), spontaneous pain signs (26.0%), persistent paw licking (22.6%), and phantom scratching (22.6%); phantom scratching, vocalization, head shaking, spontaneous pain, and air licking are specifically associated with confirmed SM in this breed.13 In Chihuahuas, scratching is the most common CM/SM-related sign (73% of dogs) and decreased postural reactions the most common neurologic deficit (87%).2 Additional neurologic signs include facial nerve deficits, seizures, vestibular syndrome, ataxia, menace deficit, proprioceptive deficits, head tremor, temporal muscle atrophy, and multifocal central nervous system signs.9 Allodynia, hyperesthesia, facial rubbing, exercise intolerance, and lethargy are also reported.10 CM alone — without SM — produces neuropathic pain in a substantial proportion of dogs;