CT measurement of the frontal sinus – Gender differences and implications for frontal cranioplasty – Review

The authors used computed tomography (CT scan) to describe forehead and frontal sinus dimensions. In the past, descriptions have been based on facial surface measurements or plain film radiography. The new approach allows them to generate a three-dimensional image.

Understanding variations in frontal sinuses can help to guide surgery in the area. (There is a great variation in individuals’ sinuses.) In addition, knowledge about gender differences can help surgeons performing facial feminization surgeries.

The article includes a table summarizing sex differences in sinus size found in previous studies. As in other studies, the average differences are not large.

The authors confirmed previously observed sex differences in this area of the face. They also found:

However, it is interesting to note that despite this, the overall width and height of the frontal sinus was generally not greater in males compared to females (with the exception of height at 10 mm to the left and right of midline). Notably, statistically significant gender variations were only found at or close to midline, in the area identified as the glabella. Here, males clearly possessed a more prominent forehead features as measured by the greater thickness of the anterior table, deeper AP dimensions, and greater overall width of the glabella. Additionally, the glabella was discovered to be more anteriorly protruding in males. 

They conclude:

Using maxillofacial CT images in the axial, coronal, and sagittal planes, we report on anatomical measurements made at discrete points throughout the forehead and frontal sinus. Our measurements of forehead and frontal sinus dimensions may serve as a normative map of the surgical anatomy in this area. Specifically, this can be useful when the physician wishes to avoid opening of the sinus during surgical procedures involving the frontal bone. Additionally, gender variations in facial anatomy have been described. These gender variations demonstrate via CT the precise degree to which variation in frontal sinus anatomy exists between genders and the locations of greatest variation. This information can be useful to surgeons who perform forehead cranioplasty for gender confirming facial surgery.

Overall, the most pronounced differences in forehead and frontal sinus anatomy were found at or near midline. This corresponds to the area of the supraorbital ridge known as the glabella and its underlying frontal sinus, which is much more prominent in males. It is important to take into account these differences in pre-operative planning for and during surgery, as the anatomical dimensions in this region make this the most likely area for frontal sinus penetration, particularly in men.

This is an important study using new technology to better understand sex differences relevant to facial feminization surgery, It may be more useful to surgeons than patients, however.

Original Article:

CT measurement of the frontal sinus – gender differences and implications for frontal cranioplasty by Matthew K. Lee, Osamu Sakai, and Jeffrey H. Spiegel in Journal of Cranio-Maxillo-Facial Surgery, 2010-10-01, Volume 38, Issue 7, Pages 494-500.