Significance of the auditory tube angle and mastoid size in chronic ear disease.

The aim of this study was to determine whether a relationship exists between mastoid size and auditory tube angle (ATA) and chronic ear disease. A radiological and clinical study was undertaken of the temporal bones of 36 subjects. There were 24 patients with unilateral chronic otitis media (COM) and 12 healthy controls (HC): the contralateral healthy ears of the COM patients were also used as control (CLHC). From each CT scan the distance between Henle spine and the sigmoid sinus (H-SS) and the ATA was assessed. The angle between a longitudinal line bisecting the transverse length of the external auditory canal and the longitudinal axis of the AT was calculated. A direct correlation between H-SS and ATA, both in COM and HC (p < 0.01), was observed, but not in CLHC (p > 0.05). There was no significant difference in the ATA results between COM and CLHC, or between COM and HC (p > 0.05), however there was a significant difference between CLHC and HC (p = 0.02). H-SS distances were not significantly different between COM and CLHC, or COM and HC, or CLHC and HC (p > 0.05). An association between ATA and mastoid size in both healthy and diseased ears was observed. The anatomical relationships of the AT, mastoid and middle ear, which form a functional unit, are not significantly important in chronic ear disease.