Imaging anatomy of the retrotympanum: variants and their surgical implications

The retrotympanic anatomy is complex and variable but has received little attention in the radiological literature. With advances in CT technology and the application of cone beam CT to temporal bone imaging, there is now a detailed depiction of the retrotympanic bony structures.With the increasing use of endoscopes in middle ear surgery, it is important for the radiologist to appreciate the nomenclature of the retrotympanic compartments in order to aid communication with the surgeon. For instance, in the context of cholesteatoma, clear imaging descriptions of retrotympanic variability and pathological involvement are valuable in pre-operative planning.The endoscopic anatomy has recently been described and the variants classified. The retrotympanum is divided into medial and lateral compartments with multiple described potential sinuses separated by bony crests.This pictorial review will describe the complex anatomy and variants of the retrotympanum. We will describe optimum reformatting techniques to demonstrate the structures of the retrotympanum and illustrate the associated anatomical landmarks and variants with CT. The implications of anatomical variants with regards to otologic surgery will be discussed.