Transcortical exposure of the antrum through the tunnel, by drilling the cortical bone at the Macewen triangle.

An antrotomy may be used in chronic otitis media surgery to observe the antrum, to do a “fluid test,” and, depending on the needs of the case, to extend the procedure to a cortical mastoidectomy.

An antrotomy will be carried out on the same temporal bone where a canalplasty has already been done. The critical Macewen triangle is shown in the figure.

EAC: External auditory canal

MAC: Macewen triangle

ZR: Zygomatic root

Having defined the Macewen triangle, the area is drilled using a 4–5mm cutting burr. The direction of the burr shaft should be parallel to the posterosuperior wall of the external auditory canal, pointing slightly inferiorly. Pointing the burr superiorly may result in damage to the temporal lobe.

II: 4–5mm cutting burr

MIL: Macewen triangle