Largest CT‐Identifiable Hypotympanic Cell and Mastoid Size

Abstract

Objective: The hypotympanum is important, especially when the surgeon confronts cholesteatomas and tumors, and when a hypotympanic cell simulates the round window niche. Hypotympanic cell size is generally considered wide-ranging and stochastic. We hypothesized that size of hypotympanic cells is not related to size of mastoid. Method: Of 41 clinically normal human crania, the 5 with the smallest mastoid pneumatization areas and the 5 with the largest areas were imaged by high-resolution computed tomography, both direct axial and direct coronal. The diameter of each ear’s largest identifiable hypotympanic cell, on either axial or coronal imaging, was measured. Results: Wide ranges were found for the largest identifiable hypotympanic cell: 0-11mm. Bilateral symmetry was found for both the largest hypotympanic cells (Spearman r = 0.68, P = .03), and for mastoid pneumatization (Spearman r = 0.66, P < .05). The diameter of the largest hypotympanic cell positively correlated with the extent of mastoid pneumatization: for left ears, Spearman r = .73, P < .03. Conclusion: The greatest diameter of largest CT-identifiable hypotympanic cells ranged from 0 to 11 mm. Even in this small series of specimens, hypotympanic cell size positively correlated with mastoid size.