Chronic mesotympanal otitis media (CMOM) is a well-developed clinical presentation that is established in diagnostics and therapy. On closer inspection, however, this principle cannot be confirmed in all its facets. Already the physiology and pathophysiology of the middle ear mucosa leave questions unanswered, starting with the distribution of the ciliated epithelium in the middle ear and mastoid to the function of gas exchange. In addition, there are new diagnostic and therapeutic approaches. In the future, optical coherence tomography could help to determine the status of the middle ear mucosa. In addition, there are new findings on the effectiveness of local and systemic antibiotics as well as antiseptics in chronic otorrhea. Other new developments include minimally invasive surgical procedures using endoscopic techniques. All this gives reason to provide an update on the topic of chronic mesotympanal otitis media, which should contribute in preparation for the specialist examination or refreshing. Basics of physiology and pathophysiology as well as new diagnostic approaches and medical treatment were covered in Part 1 of this paper. In Part 2, in addition to established methods, new developments in surgical therapy with minimally invasive surgical procedures are described in more detail.