The epitympanic compartments and the anatomy of the atticotympanic dia
phragm were examined in a pair of serially sectioned temporal bones wi
th secretory otitis media and chronic otitis media, respectively. Find
ings confirmed reports of 19th century scientists in that Prussak's sp
ace has a wide connection to the mesotympanum through the posterior po
uch of Troltsch and may have an additional narrow passage in its roof
to the lateral malleal space. The lateral incudomalleal fold regularly
separates the upper lateral attic from the lower lateral attic and th
e mesotympanum. The medial incudal fold as a rule is atrophic already
at birth. The anterior tympanic isthmus thus extends from the tenser t
ympani tendon to the posterior incudal ligament and is the main passag
e far epitympanic and mastoid aeration. Opening(s) in the tenser fold,
when present, are also important. In some ears, the posterior tympani
c isthmus may form an auxiliary narrow route for aeration via the incu
dal fossa. The isthmi may be blocked by middle ear infection, which ca
n lead to chronic mastoid and attic disease. Pathways for cholesteatom
a spread in the epitympanum are discussed.