Middle Ear Effusion Caused by Mechanical Stimulation of the External Auditory Canal:An Experimental Study in the Rat

Abstract

Mechanical stimulation of the external auditory canal (EAC) in rat, either by scratching or exposure to a stream of air, caused effusion behind an intact ear-drum both in the experimental ear and in the contralateral one. Histologically the pars flaccida appeared oedematous, especially its lamina propria; and was infiltrated by inflammatory cells indicating a vascular leakage. Determination of the histamine level of the content of the middle ear cavity showed elevated levels, not only in the experimental ear but also in the contralateral. This increased level of histamine was recorded as long as 24 hours after stimulation. Though the mechanisms involved are not known, new ideas about the initiation of otitis media with effusion are inferred.

An animal model for external otitis

“…In earlier studies, mechanical stimulation of the EAC was shown to create effusion in the middle ear cavity [3]. In the present study most rats demonstrated a slightly thickened pars flaccida, but no signs of effusion.…”

“…When challenged by pneumococcal infection, the rat ear also reacts similarly to that of the human ear [10]. An earlier study on mechanisms involved in the development of otitis media with effusion showed that sufficient mechanical stimulation of the external auditory canal (EAC) will cause an inflammatory reaction of the ear canal dermis [3]. This finding raised the question whether this procedure could be used to produce an animal model for studies on external otitis.…”

Acute otitis media develops in the rat after intranasal challenge of Streptococcus pneumoniae

“…Saline also decreased the number of middle ears with AOM. In both situations we suggest that a limited inflammatory reaction and effusion production are evoked particularly from the PF 14,22 . Middle ear effusion has been shown to contain components of the innate immune system such as lysozyme, lactoferrin, defensins, collectins, 23 and immunoglobulins, 24 which may protect against AOM development.…”

Exostoses and Cavernous Venous Formation in the External Auditory Canal of the Hooded Seal as a Functional Physiological Organ

“…It is remarkable that Fowler and Osmund in 1942 (23) succeeded in inducing new bone formation in the middle ear cavity of guinea pigs by¯ushing cold water into the EACs. Later, Alm et al (24) were able to induce middle ear effusion by mechanical and thermal stimulation of the rat EAC. These ® ndings suggest that the EAC region reacts to irritation by forming both new bone and effusion material.…”