The ethmoidal bulla is an important component of the ethmoid sinus, one of the air cavities in the skull. The sinuses provide a number of functions, including air filtration and warming. This structure is significant for clinicians because it can be used as a landmark in surgery, and may also be involved in some sinus disorders. It is visible on radiographs specifically designed to evaluate the sinuses and can also be seen in some procedures involving the sinuses.
This structure forms a bulge of ethmoidal cells that can vary in precise shape and size from patient to patient. The sinuses are, in their own way, much like fingerprints, because they form individually and look very distinct, forming a complex labyrinth of air cells. In fetal development, the ethmoid sinus is one of the first to form and it keeps developing, giving rise to structures like the ethmoidal bulla.
There are two ethmoidal bullae, one in each sinus. They are located toward the front of the skull between the eyes, and are closely associated with the boundary between the sinus and the skull cavity. Inside the ethmoidal bulla, individual cells can grow in a variety of patterns. Each structure is located just above the infundibulum, the drainage cavity that allows the contents of the sinuses to flow away so they don’t become filled with mucus.
Before surgery on the sinuses, a doctor may request medical imaging studies to look at the structures of the skull, including the ethmoidal bulla. This can provide important navigational information that will be used in surgery. It can also offer insight into why the patient experiences problems like recurrent sinus infections or eye problems, which are sometimes associated with abnormalities in sinus structure. Some facilities have technology that allows surgeons to create three-dimensional reconstructions of the sinuses for practice and training purposes so they can perform surgery with a high degree of accuracy.
Once the surgeon starts work, the ethmoidal bulla can be located as a landmark to help the doctor get oriented. Working in the twisting, honeycomb-like sinus cavities can be confusing and surgeons work with care to avoid causing injuries. Being able to locate and fixate on a structure can help the surgeon focus and perform the procedure. This might involve an activity like removing excess bone to allow sinuses to drain or correcting an abnormality that makes it hard for the patient to breathe. It is typically performed endoscopically with small instruments and a camera inserted into the sinus cavity for the surgeon to work.