The site of initial production and transport of effusion materials in otitis media serosa. A study on rat middle ear cavity.

The aim of this experimental study was to localize the site of the initial production of effusion in the middle ear cavity. Via the tympanic bulla the passage between the lateral attic compartment and the rest of the middle ear (isthmus tympanicus) was blocked with Gelfoam and/or the Eustachian tube likewise with a polyethylene tube in both normal and sympathectomized rats. Effusion was thus produced in the attic, while concomitantly dilated vessels were seen in the pars flaccida, which after a couple of days gradually withdrew in a medial direction to form a retraction pocket. Sympathectomy did not prevent the production of effusion. The stream of effusion was nasal to the promontorium and the tensor tympani muscle. Its transport seems to be influenced by the ventilation through the tympanic tube.