On the origin of the high negative pressure in the middle ear space.

It has generally been assumed that a high negative pressure in the middle ear space results from obstruction of the eustachian tube and the subsequent gas resorption through the middle ear mucosa. There is clinical evidence that quite a different mechanism is operating. The present experimental study verifies, with direct pressure recordings in cases of the retraction type of cholesteatoma and related conditions, that a high negative pressure can be generated by an active evacuation of air through the eustachian tube. The high negative pressure induced may explain the development of tympanic membrane retraction and pocketing, and the subsequent development of cholesteatoma.