A cute Cavalier King Charles Spaniel.

Chiari Malformations in Dogs

Chiari malformations (CM) are a collection of highly heritable neurologic disorders that are believed to result from a variety of malformations of the occipital bone of the canine skull. CM is caused by a discrepancy between the size of the brain and the space within the skull. The space in the skull (caudal fossa) is too small relative to the size of the brain. The result is overcrowding of the brain with herniation of the cerebellum through the foramen magnum (the site through which the brainstem passes). This can cause an obstruction in the normal flow of cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. The resulting pressure leads to a variety of clinical symptoms (see below).

Chiari malformations were originally identified in the Cavalier King Charles Spaniel and, in general, are more common in small breed dogs. Other breeds affected with chiari-like malformations include the Affenpinscher, Boston terrier, Brussels Griffon, Chihuahua, French bulldog, Havanese, Maltese terrier, Miniature dachshund, Miniature pinscher, Papillon, Pekingese, Pomeranian, Pug, toy/miniature poodle, Shih tzu, Staffordshire Bull Terrier, and Yorkshire Terrier.

Various malformations can occur concurrently with CLM, such as hydrocephalus or an intracranial arachnoid cyst. Syringomyelia (SM) is an associated disorder primarily observed in Cavalier King Charles Spaniels and is the most commonly observed Chiari malformation 10. The increased popularity of this breed, along with increased availability of neurologic imaging techniques, has proven SM to be far more common than previously believed.

Pathologically, Syringomyelia is characterized by the presence of abnormal fluid-filled chambers within the cervical spinal cord (called “syrinxes”). As such, abnormal sensations and significant neck pain are the hallmark of this disease.

Clinical Signs of Syringomyelia

Clinicals signs vary depending on the severity of the problem in the individual dog.

Symptoms may include:


Age, breed, and clinical signs are generally considered sufficient evidence for a presumptive diagnosis. The general physical examination at the vet is typically normal. However, the neurologic exam (evaluation of the nervous system) can reveal a head tilt, nystagmus, loss of balance, poor coordination, trouble walking, tremors, and/or vision abnormalities. The most common observation with CLM is pain in the neck and head regions.

Diagnostic tests may include:

Treatment of Chiari Malformation and Syringomyelia in Dogs

Treatment of chiari malformations can be difficult for severely affected dogs. The focus of treatment is on pain relief.

Treatment options include the following:

Associated Veterinary Cost

Because definitive diagnosis for chiari-like malformation and syringomyelia requires a high-tech imaging technique, the cost of diagnosis can be prohibitive for many pet owners. Typical costs for magnetic resonance imaging ranges from $1,800 to $3,100. The cost of a cerebrospinal fluid tap, including procedure fee, anesthesia, and laboratory analysis, can be approximately $700 to $1900.

The cost of treatment depends greatly on the severity of the disease. If medical management is considered sufficient, expenses are likely to remain under $60 a month for drugs most commonly employed in these cases.

Surgical management is considered expensive. Estimates ranging from $5,000 to $10,000 are common.

Prognosis for Dog with Chiari Malformations

Medical therapy appears to help symptoms in most patients. There appears to be little correlation between the MRI findings and the severity of the symptoms. Surgery is recommended and success rates range from 50% to 80%. Repeat surgery may be needed in certain cases.


Sadly, this disease is considered highly preventable via sound breeding practices. Terminating all breeding lines bearing any afflicted offspring is the ideal approach to eliminating this disease. A resource for breeders can be found here.