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Syringomyelia (SM) and Chiari Malformation (CM) in Dogs

What Are Syringomyelia (SM) and Chiari-Like Malformation (CM) in Dogs?

Chiari-Like Malformation, also known as Caudal Occipital Malformation Syndrome (COMS) or occipital hypoplasia, is a relatively rare but debilitating neurological condition found in dogs. It leads to abnormal sensations, pain, and progressive weakness.

Essentially, Chiari-Like Malformation occurs when a dog’s brain does not properly fit within its skull. As a result, a part of the brain, typically the brain stem, becomes crowded, causing an obstruction in the flow of cerebrospinal fluid. Cerebrospinal fluid is responsible for nourishing the brain and spinal cord, removing waste, and absorbing shock.

Syringomyelia, characterized by fluid pockets within the spinal cord, can develop as a consequence. This occurs when cerebrospinal fluid is unevenly distributed throughout the spinal cord. While Chiari-Like Malformation is one of the primary causes of syringomyelia in dogs, tumors and trauma have also been associated with the condition.


The main indicator of this condition is scratching, particularly around the neck, head, chest, or shoulders. This scratching behavior is unusual as it often happens while the dog is in motion, might not actually make contact with the skin, and appears to be localized to one side of the neck. Dogs may also demonstrate pain in these areas when touched, petted, or when a collar or leash is applied, and this discomfort can come and go. Additional symptoms that dogs may experience include:

  • Limited or stiff postures
  • Abnormal head positioning (the head may seem tilted or bent)
  • Gradual weakening in any limb
  • Behavioral changes
  • Facial nerve weakness
  • Hearing loss
  • Muscle wasting
  • Irregular gait or lack of coordination (i.e., a wobbly walk)
  • Seizures
  • Vocalization due to pain during activities like jumping, or when coughing, sneezing, or straining to urinate or defecate.


Chiari-Like Malformation in dogs is an inherited condition that is frequently observed in specific breeds, including:

  • Cavalier King Charles Spaniel (most commonly affected breed)
  • Chihuahua
  • Brussels Griffon
  • Fox Terrier
  • Lhasa Apso
  • Maltese
  • Miniature Dachshund
  • Pekingese
  • Pomeranian
  • Pug
  • Samoyed
  • Yorkshire Terrier

Because this condition has a genetic basis, symptoms are more commonly noticed in younger dogs.


The primary diagnostic tool for identifying Syringomyelia (SM) and Chiari-Like Malformation (CM) in dogs is MRI (Magnetic Resonance Imaging). Unfortunately, apart from MRI, there isn’t currently a screening tool available. Due to the cost and the need for anesthesia during the procedure, MRI might not be feasible for every pet owner or patient.

In addition to reviewing the provided history and symptoms, veterinarians typically begin with a thorough physical examination, focusing on the dog’s nervous system. They may also suggest a series of screening tests, including blood work and urinalysis. These tests can help rule out other potential causes such as osteoarthritis, allergies, and ear infections, while also providing insights for future anesthetic recommendations.

X-rays, while somewhat limited, can also aid in ruling out other underlying conditions that may be harmful.


The management of this condition focuses on several key objectives: alleviating pain, reducing secondary swelling and inflammation, and lowering cerebrospinal fluid (CSF) pressure.

Medications such as gabapentin, amitriptyline, or amantadine are often used to diminish neuropathic pain, which involves abnormal painful responses or stimuli associated with neurological disorders. Nonsteroidal anti-inflammatory drugs (NSAIDs) or steroids can help mitigate swelling and inflammation. Diuretics like furosemide or omeprazole, an antacid, can be employed to decrease CSF production. Veterinary acupuncture may also be considered as part of the treatment plan.

Even with surgical intervention, which involves removing a portion of the skull or vertebrae to alleviate pressure, a complete cure may not be achievable. Surgery has shown an 80% reported success rate in improving symptoms, but there is a risk of symptom recurrence later on, necessitating ongoing medical management. Unfortunately, for dogs experiencing severe symptoms and/or persistent pain that does not respond well to treatment, humane euthanasia may be a recommended option.

Recovery and Management

The prognosis for dogs afflicted with these conditions can vary significantly. While some dogs may experience minimal pain and can effectively manage their symptoms with medication alone, those facing severe pain or neurological issues tend to have a more uncertain prognosis.

Patients undergoing surgery should anticipate a multi-week recovery period, during which gradual reintroduction to exercise and scheduled follow-up appointments will be necessary. If your dog is prescribed medication, it’s likely they will need to remain on it for an extended duration, potentially for life, unless otherwise advised by your veterinarian.

Given the nature of these medications, regular follow-up appointments for drug monitoring and blood work will be essential. Additionally, implementing strategies such as elevating food and water bowls and using a harness instead of a collar and leash can help minimize discomfort and pain. It’s also advisable to avoid rough play and traumatic situations.

Collaborating closely with your veterinarian is crucial for effectively managing your dog’s condition and ensuring the best possible outcome. Since pain and symptoms may escalate over time, ongoing follow-ups and testing may be necessary to address any developments and adjust the treatment plan accordingly.

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