The Retrotympanum Revisited By a Volumetric Approach Using Synchrotron-Based X-Ray Phase-Contrast Imaging.

Area of Science:

• Anatomy
• Medical Imaging
• Otolaryngology

Background:

• The retrotympanum contains bony recesses frequently involved in cholesteatoma.
• Limited accessibility of these small structures challenges conventional imaging.
• Understanding retrotympanic anatomy is crucial for surgical planning and disease management.

Purpose of the Study:

• To systematically analyze retrotympanic subsites using synchrotron-based X-ray phase contrast imaging (SR X-PCI).
• To describe topographic relationships and volumetric characteristics of retrotympanic recesses.
• To investigate the correlation between recess volume, depth classification, and facial nerve distance.

Main Methods:

• Ten human temporal bones were analyzed using SR X-PCI.
• Microtomographic datasets were acquired and segmented.
• Key retrotympanic spaces including sinus tympani, facial recess, posterior sinus, and lateral tympanic sinus were identified and analyzed.

Main Results:

• Significant anatomical variability was observed, with sinus tympani being the largest and posterior sinus the smallest recess on average.
• Positive correlations were found between recess volumes and their depth classifications.
• An inverse correlation existed between recess volume and distance to the facial nerve.
• A novel suprafacial recess was identified in 70% of specimens.

Conclusions:

• SR X-PCI provides effective 3D visualization and volumetric analysis of retrotympanic subspaces.
• The study confirms the complex and variable anatomy of the retrotympanum.
• A consistently present, previously underreported suprafacial recess was discovered.