The dermoid sinus is a congenital abnormality, a rare genetic mutation found in some dogs and occasionally cats. In medical terms, it is also referred to as a dermoid cyst, an African cyst or a hair cyst. The dermoid sinus is also called a neural tube defect. When a puppy is still a developing embryo in the womb, the neural tube which will eventually become the puppy’s spine should separate from the skin. If the separation fails to occur, the dermoid sinus will grow in its place. The sinus may either remain connected to the spinal canal or in a blind sac once the puppy is born.
The dermoid sinus is a genetic skin disorder that can be found among certain dog breeds. Breeds that are likely to be born with the neural tube defect are the Rhodesian Ridgeback and Thai Ridgeback. A study has reported that 8 to 10% of Rhodesian ridgebacks in Sweden have dermoid sinus. Other likely breeds with dermoid sinus are Kerry Blue Terriers, Boxers and Shih Tzus, as well as mixed breed dogs with a Rhodesian ridgeback heritage.
The dermoid sinus is a structure that lies below the skin of the dog’s back. It is a tubular skin indentation that can go as deep as the spinal canal. The sinus sometimes appears in the rump or the spinal cord covering, but is commonly found in the cervical neck area of the pup, which is connected to the spinal cord. The sinus can also be found on midline of the neck, back and tail of the dog’s spinal column. The tracts can be single or multiple. Should the dermoid sinus be infected with bacteria, it will result into a dermoid sinus infection.
The dermoid sinus tract can be detected by shaving the skin where the sinus is attached. This is usually a group of hairs that protrude straight up from the pup’s hair coat. If a small, pore-like opening with a tuft of hair is found upon shaving, this is the confirmation of a dermoid sinus infection. Other symptoms of a dermoid sinus are a cyst-like swelling on the back and draining tracts on the dog’s skin along the ridge. As the puppy grows older, the more pronounced the dermoid sinus is. The bacteria can get into the pore-like opening and breed there, forming an abscess. The abscess will eventually rupture and drain as a purulent wound, resulting into an inflammation.
The sinus is a thick-walled neural tube that is made up of fibrous tissue and is lined up with skin cells. It can contain oil, hair, and skin debris, making it a potential breeding ground for bacteria. A dermoid sinus infection can lead to swelling of the spinal cord, the spinal cord covering, and even the brain, causing neural complications for the affected pup. Young animals are the ones commonly affected, though they will not show symptoms until later on. Because the sinus is connected to the spinal cord, the infection of the sinus sends intense pain signals to the nervous system of the affected pup.
A non-infected dermoid sinus normally does not cause problems while it remains dormant. However, once it gets infected, then complications begin. A dermoid sinus infection can be very painful for the dog, and in worst cases, fatal. A life-threatening infection is called a Category IV sinus. Category IV sinuses are those connected to the spinal cord, risking infections on the tissues. The dermoid sinus infection can also result into more complicated diseases such as meningitis, the inflammation of the brain and spinal cord covering, and myelitis, the inflammation of the spinal cord. Symptoms of this include pain, fever and body rigidity.
If a dog has a dermoid sinus infection, call a veterinarian immediately. Administer the recommended medication. There is no known prevention for the formation of the dermoid sinus. Should a dog be found to have dermoid sinus, the dog should be neutered immediately. Dogs with a dermoid sinus infection condition should not be used for breeding. This way it will stop the gene from spreading to other dogs. There is a debate on whether the gene is recessive or polygenic – meaning it involves multiple genes – which is why it is highly advisable for dog breeders not to breed a dog which is a known carrier of the gene. Application of folic acid supplements to the bitch before and during pregnancy may also lower the potential occurrence of the condition.
Affected pups are usually put to sleep if the infection is already widespread. The owners can also choose to have the pups undergo surgery to remove the dermoid sinus. It is advisable to contact a veterinarian who has experience on dermoid sinus infection removal. There are some cases where the sinus is tightly wrapped around the spinal cord, making it impossible to remove even with surgery. The healing period may also be traumatic for the pup, as complicated cases give rise to serum build on the surgical site. Aspiration using a large gauge and needle must be administered three times daily, usually after three days of the surgery. This can last up to ten days, if tissue damage is severe. Occasionally, the sinus may grow on the spine again.
The following diagnosis can be helpful to check for possible infections: Initial tests include a complete blood count, urinalysis, and a check on the biochemical profile. To determine how deep the sinus is, a myelogram, which is a dye X-ray study, or fistulogram, which is a dye injection that will show up white on an X-ray, can be performed. Radiographs and X-rays of the spine and the soft tissues will also check for the dermoid sinus infection presence. Should the dog be exhibiting neurological signs and symptoms, computed tomography (CT) and magnetic resonance image (MRI) can be administered. If the sinus is found to be dormant or not deep enough, it may not require excessive treatment. However, if the infection has already spread to the dog’s nervous system, the dog may never fully recover from the surgery.