Caudal Occipital Malformation Syndrome and Syringomyelia
Medically reviewed by Dr. Carrie Jurney, DVM, DACVIM (Neurology), board-certified veterinary neurologist.
Caudal occipital malformation syndrome (COMS), also called Chiari-like malformation, is a condition where the back of a dog’s skull is too small for the brain. The crowding blocks the normal flow of spinal fluid, which can lead to fluid pockets in the spinal cord (syringomyelia) and pain. It’s most common in Cavalier King Charles Spaniels and other small breeds, and it’s diagnosed with an MRI.
Introduction to Caudal Occipital Malformation Syndrome (COMS)
Caudal Occipital Malformation Syndrome (COMS) involves a malformation at the back of the skull, leading to insufficient space for the posterior part of the brain. As a result, the cerebellum, a part of the brain, is displaced from its normal position and begins to herniate, or exit the skull. This displacement disrupts the normal flow of spinal fluid, potentially causing a buildup of fluid in the spinal cord, known as syringomyelia (SM), and an enlargement of the brain's fluid spaces. The latter condition is termed ventriculomegaly or hydrocephalus, depending on the severity.
COMS is most commonly diagnosed in young adult Cavalier King Charles Spaniels, but it can occur in dogs of any age and has been identified in various small breeds. While reports indicate that up to 95% of Cavalier King Charles Spaniels may have this malformation, a significantly smaller percentage exhibit symptoms. COMS is rare in cats, but it does occur; about half of feline cases are in Persians.
What Is Syringomyelia In Dogs?
Syringomyelia (SM) means fluid-filled pockets, called syrinxes, have formed inside the spinal cord. In dogs with COMS, the crowded back of the skull disrupts the normal flow of spinal fluid, and fluid builds up within the cord, most often in the neck.
Not every dog with COMS develops syringomyelia, and not every dog with syringomyelia shows signs. The most common sign is “phantom” or “air guitar” scratching: scratching at the neck or ears without actually touching the skin. Other signs include neck pain, sensitivity to touch around the head and neck, yelping when picked up, and sleeping with the head raised.
Because the syrinx is inside the spinal cord, it can’t be seen on X-rays. An MRI is the only way to confirm it and see how large it is.
Symptoms of COMS-SM (Caudal Occipital Malformation Syndrome with Syringomyelia)
Dogs with COMS-SM may exhibit a range of symptoms, including:
Scratching at the neck and ears, frequently without making actual skin contact, a behavior known as “phantom scratching” or “air guitar.”
Head and neck pain.
Incoordination and weakness.
Abnormal curvature of the neck, or scoliosis.
In some cases, seizures, facial paralysis, and deafness are also reported.
How COMS Is Diagnosed
Diagnosis starts with a neurologic exam, where a veterinary neurologist checks your dog’s reflexes, coordination, and where they’re painful. If COMS or syringomyelia is suspected, the next step is an MRI of the brain and neck.
MRI is the only test that clearly shows the shape of the back of the skull, how crowded the brain is, and whether fluid pockets have formed in the spinal cord. It also helps rule out other conditions that cause similar signs, like disc disease or inflammation.
Remedy has an MRI on site, so your dog’s exam, imaging, and treatment plan can all happen in one place. Dogs are placed under anesthesia for the MRI so they stay perfectly still. You can find current consultation and MRI fees on Remedy’s price list.
Treatment for COMS-SM
COMS-SM can be treated through both medical and surgical approaches. Medical treatments primarily focus on reducing spinal fluid production and managing symptoms such as pain and seizures. While these treatments can effectively control symptoms in many patients, they do not address the root cause of the condition, and not all dogs respond to medical therapy.
Surgical intervention involves removing the piece of bone causing compression on the brain, thereby facilitating more natural spinal fluid flow. The operated area is typically covered with a material to minimize scar formation. Depending on the specifics of your pet’s condition, the neurologist may recommend alternative surgical procedures, like placing a shunt to drain excess brain fluid. The primary goals of surgery are to alleviate pain, reduce symptoms like scratching, and prevent symptom progression. Approximately 80% of dogs show improvement post-surgery. However, some dogs may still require medication, often at a reduced dosage, with better symptom management. In about 20% of cases, restrictive scarring at the surgical site can occur, potentially leading to issues similar to the original condition.
Prognosis & Life Expectancy For Dogs With COMS
COMS is a lifelong condition. Many dogs can be managed and live comfortably with the right treatment, but in severe cases it can be life-limiting: about 15% of cases become severe enough to warrant euthanasia. The outlook depends mostly on how severe the pain is, whether syringomyelia is present, and how well your dog responds to treatment.
With medication: many dogs’ pain and scratching can be controlled with medication, though signs can progress over time and doses may need adjusting. Regular rechecks help your neurologist keep your dog comfortable.
With surgery: about 80% of dogs improve after surgery. Some still need medication afterward, often at a lower dose. In about 20% of cases, scar tissue can form at the surgical site and cause signs to return.
The biggest factor in quality of life is keeping pain under control. If you notice more scratching, more neck pain, or changes in how your dog moves, let your neurology team know early.
Medications Used in Treatment of COMS-sM
Gabapentin or Pregabalin
Omeprazole
Amantadine
Integrative Therapies that may be helpful
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Caudal occipital malformation syndrome (COMS), also called Chiari-like malformation, is a condition where the back of the skull is too small for the brain. It can block the flow of spinal fluid and lead to syringomyelia, fluid pockets in the spinal cord that can cause pain.
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COMS is most common in Cavalier King Charles Spaniels, and up to 95% of Cavaliers may have the malformation, though far fewer show signs. It has also been found in other small breeds, and rarely in cats, where about half of cases are in Persians.
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A dog with phantom scratching, also called “air guitar” scratching, scratches in the air near the neck or ear without actually touching the skin. It’s the most common sign of syringomyelia.
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With a neurologic exam followed by an MRI of the brain and neck. MRI is the only test that shows the malformation and any fluid pockets in the spinal cord. Remedy has an MRI on site.
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Yes. Many dogs are managed with medications that reduce spinal fluid production and control pain. Medication doesn’t fix the malformation, and not every dog responds, so surgery may be recommended for some dogs.
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Many dogs with COMS can be managed and live comfortably with treatment, though signs can progress over time. In severe cases the condition can be life-limiting: about 15% of cases become severe enough to warrant euthanasia. The outlook depends on how severe the pain is, whether syringomyelia is present, and how well your dog responds to treatment.
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Costs depend on whether your dog needs an MRI, medication, or surgery. Remedy’s neurology team will give you a detailed estimate after the exam. Current fees for consultations, MRI, and Chiari malformation surgery are listed on Remedy’s price list.
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