Caudal Occipital Malformation Syndrome and Syringomyelia

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.

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.

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.