The abnormally large frontal sinus. I. A practical method for its determination based upon an analysis of 100 normal patients.

One hundred normal Caldwell view radiographs were examined on patients who had no signs or symptoms referable to the frontal sinuses. Magnification factors were determined for Caldwell views obtained on a dedicated head unit and as part of a skull series. The areas of the frontal sinuses were actually measured with a Zeiss Videoplan 2 computer and corrected for magnification. The area variation in this normal population was determined. Four linear measurements were individually correlated with these areas. Two of these lines had excellent correlation with the sinus area and if either of these lines exceeds a calculated value, the sinus area exceeds the 99th percentile of the normal population and can be considered abnormally enlarged. This technique provides a rapid, easy, and reliable method for assessing abnormally enlarged frontal sinus areas.