ABSTRACT
The frontal sinus is arguably the most complex of the paranasal sinuses. It demonstrates great variability in size and septation and is rarely symmetrical. This chapter discusses the complex anatomy of the frontal recess and frontal sinus. The frontal recess is bound anteriorly by the agger nasi and the frontal process of the maxilla, the frontal beak. In order to build a three-dimensional understanding of the frontal recess, computed tomography (CT) images in the coronal, axial and parasagittal planes are required. Type 4 cells are rarely isolated within the frontal sinus and usually pneumatize from the frontal recess. They can be extensive and cause disease by direct obstruction of the outflow tract or be diseased themselves. Magnetic Resonance Imaging (MRI) is very helpful in assessing the dual interfaces between the nasal cavity, and the orbit and the intra-cranial cavity. It is recommended that in cases of unilateral sinus disease, both CT and MRI are routinely performed.
