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Hypothesis: The aim of this study was to investigate the anatomy and pathology of the anterior epitympanum and of the tensor fold., Background: Early studies reported data that are primarily still relevant, but contemporary reports present conflicting data, including several erroneous concepts., Methods: Fifty-one temporal bones were dissected, and the anatomic details were photographed in 42 normal and nine infected bones. Histology was documented from seven serially sectioned bones, five normal and two infected., Results: The tensor fold formed the frontal wall of the anterior epitympanum between tensor tendon and attic bony wall, the anterior insertion consisting of composite connective and fatty tissue with some bone trabeculae. The transverse crest was posterior to it and extended from the anterior tympanic spine to the facial canal. The tensor fold angle in 78% of the specimens was between 45 degrees and 80 degrees, seldom horizontal, and the size of the supratubal recess (or space) increased as the fold angle increased. In 14 ears (27%) the fold had a membrane defect connecting the two spaces. Blockade of the tympanic isthmus caused inflammatory obliteration of the anterior epitympanum when the tensor fold was intact., Conclusions: The anterior epitympanum, a closed space around the anterior half of the head of the malleus, is normally closed by an intact tensor fold, but about one fourth of ears may show membrane defects. Aeration occurs via the tympanic isthmus through a constriction formed by the head of the malleus with the medial attic wall. In surgery for ears with epitympanal pathology, incus transposition should be combined with resection of the thin portion of the tensor fold for safeguarding permanent attic aeration.

The epitympanic compartments and the anatomy of the atticotympanic diaphragm were examined in a pair of serially sectioned temporal bones with secretory otitis media and chronic otitis media, respectively. Findings confirmed reports of 19th century scientists in that Prussak's space has a wide connection to the mesotympanum through the posterior pouch of Tröltsch 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 the mesotympanum. The medial incudal fold as a rule is atrophic already at birth. The anterior tympanic isthmus thus extends from the tensor tympani tendon to the posterior incudal ligament and is the main passage for epitympanic and mastoid aeration. Opening(s) in the tensor fold, when present, are also important. In some ears, the posterior tympanic isthmus may form an auxiliary narrow route for aeration via the incudal fossa. The isthmi may be blocked by middle ear infection, which can lead to chronic mastoid and attic disease. Pathways for cholesteatoma spread in the epitympanum are discussed.