Surgery for Caudal Occipital Malformation

Introduction to Surgery for COMS

Caudal Occipital Malformation Syndrome (COMS) is a malformation of the back of the skull that causes compression of the underlying brain. It can occur in a variety of small breed dogs, but is commonly found in Cavalier King Charles Spaniels. There are a variety of medical treatments available for this condition, however pet’s with symptoms that do not respond to medical therapy, or have severe symptoms may need surgeries.

Surgical Procedure

Surgery for COMS involves removing the bone from the skull and sometimes the first cervical vertebrae to relieve pressure on the underlying brain and spine. After the bone is removed, the soft tissues, including the covering of the brain called the dura, are opened and tacked to further relieve the compression. Finally, a custom molded plate will be placed to cover the hole we have made in the bone.

Some pet’s will also have a build up of fluid in front of the malformation, called hydrocephalus. In some cases, the neurology team may recommend a surgery to place a shunt. The shunt is a tube that drains fluid from the brain into the abdomen where it can be absorbed safely by the body.

Recovery

Pet’s typically stay one to two nights in the hospital after this procedure. After they return home, they need to be kept relatively quiet for the first two weeks so they can heal. They do not need to be crate-confined necessarily, but we don’t want them to be too active and open their sutures. Please limit exercise to 3 short leash walks a day.

Most pets will need medications two to three times a day while they are recovering. They do not need constant supervision for recovery.

Expectations and Prognosis

The majority of dogs (80+%) will experience relief from this surgery. Symptoms like pain are the most likely to respond to surgery, while other symptoms like seizures are unlikely to respond. Surgery can also provide relief for dogs who have developed problems walking.

Unfortunately, approximately a third of dogs will have scar tissue that forms where the bone was removed and will have a relapse in signs. This scar tissue can form as soon as a month after surgery, but may take longer to develop. This means long term, this surgery is likely to help about half of the dogs who have it.

Some dogs will continue to require medications long term after surgery. The neurology team will guide you on what is appropriate for your pet.