In classifying the origin of acquired cholesteatoma, Ruedi proposed which mechanism as the primary cause of the most common pars flaccida cholesteatoma?

• A Retraction pocket formation in pars flaccida due to chronic Eustachian tube dysfunction ✓
• B Metaplasia of middle ear respiratory mucosa to squamous epithelium
• C Epithelial migration through a marginal tympanic membrane perforation
• D Squamous epithelium implantation following trauma or surgery

Explanation

The retraction pocket (invagination) theory, strongly associated with Toss's classification, is the dominant mechanism for pars flaccida cholesteatoma: chronic Eustachian tube dysfunction leads to negative middle ear pressure causing invagination of the pars flaccida of Shrapnell's membrane into the epitympanum. The keratin-producing epithelium at the base of this pocket accumulates desquamated layers, progressively deepening into a cholesteatoma. Epithelial migration theory explains pars tensa (marginal) cholesteatoma; metaplasia theory is proposed for congenital types; implantation follows iatrogenic seeding. The retraction pocket mechanism explains the characteristic location at the posterosuperior quadrant/attic.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.