Possible clinical implications of the structural variations between the tympanic membrane quadrants

Area of Science:

• Anatomy
• Otolaryngology
• Medical Imaging

Background:

• Retraction pockets and marginal perforations of the tympanic membrane (TM) predominantly occur in the superior posterior quadrant (SPQ).
• Patulous Eustachian tube dysfunction also frequently manifests in the SPQ.
• Structural variations in the TM may underlie these common clinical observations.

Purpose of the Study:

• To investigate the anatomical characteristics of the four quadrants of the pars tensa of the human tympanic membrane.
• To determine the surface area and thickness of each TM quadrant.
• To correlate TM structural variations with the common sites of ear pathologies.

Main Methods:

• The pars tensa of 23 human adult temporal bones was divided into four quadrants using anatomical landmarks.
• Surface areas of each quadrant were measured using graph paper and photography.
• TM thickness was measured using microscopy in 20 additional temporal bones, with four measurements per quadrant.

Main Results:

• The superior posterior quadrant (SPQ) was found to be the largest, comprising 31% of the pars tensa area.
• The SPQ was significantly thinner (69 μm) compared to the other quadrants (approximately 85 μm).
• Radial measurements decreased from the SPQ towards the anterior-superior quadrant.

Conclusions:

• The SPQ is the largest and thinnest quadrant of the tympanic membrane.
• Variations in the middle fibrous layer contribute to the differential thickness of TM quadrants.
• These anatomical findings support the hypothesis that TM structure influences the predilection for certain pathologies in the SPQ, particularly those related to Eustachian tube dysfunction.