INCUDAL FOLDS AND EPITYMPANIC AERATION

Thirty-seven temporal bones were dissected and the posterior tympanic and epitympanic folds recorded and photographed. Histologic details we re documented from four serially sectioned temporal bones, two normal and two inflamed. Of these 41 specimens, 31 were normal, and 10 showed signs of inflammation. The type for the lateral fold was incudomallea l in 16 and incudal in 25 ears. Incus intercrural and incudostapedial folds appeared only exceptionally. Medial and superior incudal folds w ere not present in normal ears. The anterior tympanic isthmus was a co nstant, large aeration pathway. In chronically inflamed ears, its part ial or total block was caused by polypoid or large sheet-like folds. I nactive sequelae appeared as mature, simple, one-layer or extensive mu ltilayer networks of webs, connected with a deeply indrawn incudomalle al fold. The small posterior isthmus was open to the incudal fossa in 13 ears, and in 28, it was sealed off by a posterior incudal fold. The mastoid air cell tracks were (in ten of 37 dissected ears) open to th e incudal fossa, or directly, to the posterior tympanum. Auxiliary pat hways due to membrane defects were found in both the horizontal and de scending portions of the incudomalleal fold. Excepting the chordal, in cudomalleal, and posterior incudal folds, fold-like webs in the poster ior tympanum and epitympanum are of inflammatory origin.