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.