Nasal dermoid tracts are rare conditions in which a dermoid cyst is present under the skin of the nose. A dermoid cyst is a sac-like structure that forms because some cells that should be on the outside of the body, like skin cells, are trapped under the skin during development as an embryo. In the nose, they can cause problems because there can be a lump, which can be seen and felt, and there is often a very small hole in the skin of the nose, which can discharge fluid. Removing these is not as straightforward as dermoid cysts elsewhere in the body as they can lie partially under the skin of the nose but also can extend between the bones of the nose and the front of the skull so that part of them is inside the skull.
We work as a multidisciplinary team with pediatric plastic surgeons, pediatric neurosurgeons and pediatric radiologists to undertake a thorough assessment of the position and extent of the nasal dermoid tract and plan the operation necessary to remove it.
Nasal dermoids occur in about one in 30,000 children. During early development as an embryo, skin or skin-like tissue is trapped under the rest of the skin, and it becomes a cyst, which is a sac-like structure under the skin. Sometimes, there can be a connection from this cyst to the skin surface, and this can be seen as a small hole on the bridge or tip of the nose, often with a hair growing from it. The trapped skin in the cyst continues to do the job of skin, and so the cyst can contain hair, fluid and old skin cells.
The concern with these cysts is that they tend to grow over time and can become repeatedly infected. If they do extend within the skull, they can lie against the outer coverings of the brain, so repeated infections can cause meningitis or an intracranial abscess, which is a collection of infection within the skull and requires surgery to treat. For these reasons, removal is advisable in most cases.
There are no real separate types of the condition, but differences between people affected are the size of the cyst, whether there is an opening to the skin and whether it extends into the skull or not. The size varies between patients from a cyst that is not at all visible to a large obvious lump wider than the bridge of the nose. The opening to the skin is usually very small and may only be noticeable because of a hair that is often found at this point. In terms of whether it extends into the skull or not, this is best identified by imaging, in the form of a CT or MRI scan. It is important to know this before going ahead with any surgery, because leaving any of the cyst behind means that it is likely to re-grow and continue to become infected.
Children are affected by this in various different ways. Some children have a noticeable bump under the skin; whereas, others have nothing that can be seen by others. Unless they become infected, they tend not to be tender or painful, and some children only realize that they have a nasal dermoid tract when it becomes infected or starts leaking from the skin opening, which can happen at any time but often happens in the first few years of age. When the cyst is very large, it can distort the cartilages or bones of the nose, or the space between the eyes, which can create noticeable facial changes. After it is removed, there is almost always a scar on or near the nose, which can be noticed by others, and there is the risk of the cyst recurring after surgery.
The cause of nasal dermoid tracts is that surface cells are trapped under the skin at a very early stage in the development of the embryo. There is nothing that the mother could have done to cause or prevent it. There can be no symptoms for many years, but symptoms of nasal dermoid tracts include a lump that you can feel or see, fluid or ‘cheese-like’ material coming out of the skin opening and tenderness with warmth and redness of the overlying skin when the cyst becomes infected.
The reasons to treat nasal dermoid tracts are that they tend to grow over time, because they can discharge fluid and solid material through the skin hole repeatedly, and because they risk becoming infected, which can result in serious complications. Treatment of these involves surgery, and the extent of that surgery is variable. In small cysts that are entirely under the skin, it may be possible to remove the cyst only with a small scar under the nose, but with more extensive cysts, or those that have an opening on the skin of the nose, it is unavoidable to leave a scar on the nose as a result of surgery. This tends to be a vertical scar on the bridge of the nose, which heals and settles well.
With cysts that extend through the skull, removal involves surgery by both a pediatric plastic surgeon and a pediatric neurosurgeon. Removing the part of the cyst outside the skull is done in much the same way as a cyst that doesn’t extend into the skull, but the inside part needs to be reached by removing a small window of bone at the front of the skull. This tends to be done through a scar in the hairline. By using this combination, the surgical team can reach all of the different parts of the cyst to ensure the best chance of removing the cyst completely so that it doesn’t cause more problems.
Aftercare is important in nasal dermoid tracts due to the risk of the cyst re-growing, so we usually plan to keep patients under review for several years and plan on at least one MRI scan after surgery, usually starting a year after surgery. We offer an in-house multidisciplinary team of pediatric plastic surgeons, pediatric neurosurgeons, pediatric radiologists and clinical psychologists, all of whom have extensive experience in treating this condition.
There is no lab test to diagnose a nasal dermoid tract, and reaching a diagnosis involves asking questions about whether any lump has changed in shape of size, whether there has ever been any discharge through the skin and whether there have ever been any symptoms suggesting that it has been infected, together with a physical examination of the child. To evaluate the full shape and extent of the cyst, CT and/or MRI imaging is most likely to be requested. Once this has been evaluated, the best type and timing of surgery can be determined.
Signs to look for include: