Experimental results do not support a gas reserve function for the mastoid

The mastoid is an aerated extension of the middle ear gas pocket whose stat e of development was shown to be an indicator of past and future otitis med ia experience. While the function(s) of the mastoid is not known, a number of hypotheses has been advanced to explain the reported association between mastoid size and middle ear disease. These include the hypotheses that, wi th respect to the middle ear, the mastoid functions as a pressure buffer, a gas reserve, and/or a pressure regulator. In this paper, a physical model of the mastoid is presented that makes specific predictions against which t he validity of the hypothesized gas reserve function could be tested. Data from three published clinical experiments were evaluated for consistency wi th the predictions of the model, and the hypothesis was rejected. Also, whe n reinterpreted within the context of the model, the published data do not support a pressure-regulating function for the mastoid. (C) 2000 Elsevier S cience Ireland Ltd. All rights reserved.