Correlation between mastoid pneumatization and position of the lateral sinus.

The distance between the lateral sinus and the external ear canal was measured in 148 patients (150 ears) with completely sclerotic (nonpneumatized) mastoids and in 75 healthy random control subjects (150 ears), with pneumatized mastoids. A highly significant difference (p less than .0001) was found between the two groups, the mean distance (+/- SD) among patients being 7.8 +/- 1.7 mm, while among controls it was 13.5 +/- 2.8 mm. Moreover, a significant positive correlation (p less than .001) was found within the pneumatized control group itself, between the sinus' distance and the degree of mastoid pneumatization. The results of this study may be interpreted by those who espouse environmental theories as denoting that infantile otitis media will determine the position of the lateral sinus. However, those who favor the genetic explanation may maintain that since the position of the sinus is established prenatally and involves organogenetically the shape of the skull, the final position is unlikely to be influenced by postnatal otitis media.