Unmitigated negative nasopharyngeal pressure is associated with attic retraction pocket formation: LaPlace's law in action.

Background: Decades of clinical observation have led our subspecialty team to suspect that negative nasopharyngeal pressure is associated with attic retraction pocket formation. Furthermore, LaPlace's law, which states that the pressure within a sphere varies with the inverse of the radius, provides the dynamic explanation for why the attic area of the tympanic membrane tends to retract more frequently than the pars tensa.

Methods: The attic retraction pockets of 154 patients were classified into grades of severity (grades I-V). Impedance audiometry of middle-ear pressure was measured in the resting state, and after sniffing, swallowing and the Valsalva manoeuvre.

Results: Negative nasopharyngeal pressure (sniffing) caused a diminution of middle-ear pressure of -5 daPa on average in normal ears, and of -24 daPa to -45 daPa for tympanic membranes with attic retraction pockets of grade I to grade V.

Conclusion: Attic retraction pockets are associated with greater collapse of middle-ear volume when negative pressure is created in the nasopharynx. LaPlace's law, and the composition of the pars flaccida, suggests an explanation for why the attic region retracts more than the pars tensa.