Features of retracted (atelectatic) and ballooned (hyperectatic) tympanic membranes. (Otoscopic Clinic).

Otologists regularly observe and treat retracted (atelectatic) tympanic membranes (figure 1). Atelectasis is accompanied by a clearance deficiency in the external ear canal. It can be complicated by infection and conductive hearing defects related to ossicular destruction. (1,2) A less common entity is a ballooned (hyperectatic tympanic membrance (figure 2). Hyperectasis is not usually associated with a deficiency in external canal clearance. Therefore, infection is less common, an d hyperectasis receives less attention from otologists.

In atelectasis, the air pressure behind the tympanic membrane is lower than that of the outside atmosphere (3,4); in hyperectasis, the pressure behind the membrance is higher. (5)

In some cases, a patient will have atelectasis in one ear and hyperectasis in the other. Another interesting feature of these two conditions is that hyperectasis is sometimes preceded by atelectasis, and vice versa. Even ears that have undergone a canal-wall-up operation for retraction pocket cholesteatoma can eventually develop a ballooned tympanic membrane.

The conclusion that can be drawn from the waxing and waning behavior of the tympanic membrane is that the middle ear pressure in these ears is unstable, vacillating from a pressure greater than that of the outside atmospheric pressure to pressure less than the outside atmosphere for a period of days, weeks, or months. Both retraction and ballooning can be seen clearly because the tympanic membrane in affected patients is atrophic and lends itself to stretching outward or inward as the case may be.

Another conclusion that can be drawn is that atelectasis and hyperectasis are not related to any obstruction or insufficiency of the eustachian tube itself. Rather, these conditions are related to a disorder in the regulation of the eustachian tube function as an aerator, which might be related to a disorder in functional feedback. In other words, the process that "tells" the tube whether to introduce more or less air into the middle ear is irregular or faulty, which results in either overaeration (ballooning) or underaeration (retraction).

References

(1.) Buckingham RA, Ferrer JL. Reversibility of chronic adhesive otitis media with polyethylene tube, middle ear air-vent, kodachrome time lapse study. Laryngoscope 1966;76:993-1014.

(2.) Sade J, Avraham S, Brown M. Atelectasis, retraction pockets and cholesteatoma. Acta Otolaryngol 1981;92:501-12.

(3.) Buckingham RA, Ferrer JL. Middle ear pressures in eustachian tube malfunction: Manometric studies, Laryngoscope 1973;83:1585-93.

(4.) Sade J, Halevy A, Hadas E, Clearance of middle ear effusions and middle ear pressures. Ann Otol Rhinol Laryngol 1976;85(Suppl 25 Pt 2):58-62.

(5.) Sade J. Hyperectasis: The hyperinflated tympanic membrane: The middle ear as an actively controlled system. Otol Neurotol 2001;22:133-9.

From the Hearing Research Laboratory, Department of Biomedical Engineering, Faculty of Engineering and Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Tel Aviv, Israel. E-mail; [e-mail].