Retraction of tympanic membrane touching the promontory. It is

Retraction of tympanic membrane touching the promontory is called atelectasis. When the tympanic membrane is thin and atrophic a segment of it or the entire membrane may collapse due to eustachian tube insufficiency. It may get plastered onto a promontory and also wrap around the ossicles. Stage Ill is also called as middle ear atelectasis. Tympanic membrane comes to lie on the promontory and ossicles. Middle ear space is totally or paially obliterated but middle ear mucosa is intact. The tympanic membrane can be lifted from the promontory with suction tip. It also balloons up when N2O is used during anaesthesia. The tympanic membrane is thin because it's collagenous middle layer had been absorbed due to prolonged retraction. In these cases, long process of the incus and stapes superstructure are absorbed. Placement of the ventilation tube helps to restore the position of the tympanic membrane. Ref: PL Dhingra; 7th edition of Ear, Nose and Throat; Pg no 79