Dimeric Segment

 

The pars tensa of the tympanic membrane is composed of three layers: the skin of the external ear canal on its lateral surface, the mucous membrane of the middle ear on its medial surface and the middle fibrous layer. 

Sometimes when a perforation of the tympanic membrane heals, the fibrous layer does not regenerate. The two epithelial layers then come together to form a thin segment within the tympanic membrane. These can easily be confused with perforations.