[Ventilation and passages in the middle ear. A study by HRCT in patients with attic cholesteatoma].

Operative records of 75 patients with acquired attic cholesteatoma were evaluated and compared with preoperative HRCT findings. The cholesteatoma extensions were classified into five groups as follows; Group 1 (cholesteatoma limited to the attic, 9 cases), Group 2 (cholesteatoma occupying both the attic and the aditus, 5 cases), Group 3 (cholesteatoma extending down to the posterior tympanum, also occupying an area as in Group 2, 6 cases), Group 4 (cholesteatoma occupying the attic, the aditus and the mastoid antrum, 14 cases), and Group 5 (cholesteatoma extending down to the posterior tympanum, also occupying an area as in Group 4, 41 cases). Ventilatory conditions, or the existence of soft tissue density, were evaluated by HRCT at such locations as the supratubal recess, mesotympanum, anterior and posterior parts of the tympanic isthmus, epitympanum, and mastoid antrum. Results are as follows. In Group 1, all these locations were aerated with the exception of a few cases. In Group 2, complete opacification was observed in almost all of the antrums. Soft tissue masses involved the anterior and/or posterior parts of the tympanic isthmus in both Groups 3 and 5. In Group 3, the posterior part of tympanic isthmus was less aerated than the anterior part of tympanic isthmus. In Group 5, all locations were filled with soft tissue density except the supratubal recess and the mesotympanum, where some degree of aeration was observed. These results indicate that blockage of the ventilatory passages is not essential for formation of an attic cholesteatoma. Soft tissue density in HRCT is not the cause, but rather, the result of extension of a cholesteatoma.