SHRAPNELL MEMBRANE AND MASTOID PNEUMATIZATION

Objective: To assess whether a correlation exists between the degree o f pars flaccida (PF) retraction and the degree of mastoid pneumatizati on. Design: The degree of PF retraction was defined by means of an ope rating microscope and a pneumatic otoscope. Degree of mastoid pneumati zation was assessed planimetrically, using mastoid x-rays. Setting: Pr ivate otologic clinic. Participants: A total of 595 ears, with intact pars tensa, of 332 adult patients. Results: The degree of PF retractio n was found to be inversely correlated to the level of mastoid pneumat ization. Poorly pneumatized mastoids were associated with PF retractio ns. The poorer the pneumatization, the deeper the retraction. Well-pne umatized mastoids were associated with normal position of the PF. Conc lusions: This study lends further support to the possibility that the mastoid pneumatic system functions as a middle ear pressure buffer, Th is possibility gives further explanation as to why cars with poorly pn eumatized mastoids tend to develop tympanic membrane retractions and p erforations, incus necrosis, or retraction pocket cholesteatoma, while ears with a large pneumatic system are rarely at such risk.