Pars flaccida retraction and mastoid size: relationship in clinically normal specimens.

BACKGROUND: The relationship of pars flaccida retraction with epitympanic aeration and mastoid size is ill-defined. Both pars flaccida retraction and small mastoid size are traits of nearly all clinical entities of otitis media.

OBJECTIVES: To determine, in clinically normal specimens, the relationship of pars flaccida retraction with mastoid pneumatisation and epitympanic aeration.

STUDY DESIGN: Post-mortem anatomical dissection of 41 bequeathed adult crania without clinical otitis.

METHODS: Pars flaccida retractions were viewed with an operating microscope and judged using Sade's classification. Mastoid sizes were determined radiographically (by plain Law lateral images). Ten crania, five with the largest mastoids and five with the smallest mastoids, were studied by computed tomography.

RESULTS: No specimen had a retraction worse than Sade grade two (i.e. retracted onto the neck of the malleus). Retractions were unrelated to the extent of mastoid pneumatisation. All epitympani were found to be normal on both anatomical dissection and computed tomography imaging.

CONCLUSION: Pars flaccida retraction is probably related to prior, presumably transient, non-aeration of Prussak's space.