中耳コレステリン肉芽腫の成因

Abstract

Cholesterol of cholesterol granulomas is found in pooled fluid in the mastoid antrum and in the granulation tissue. The cholesterol may be related to erythocytic membranes rich in freecholesterol. The reasons why erythrocytes exude and why cholesterol precipitates remain unknown.In surgical cases of cholesterol granuloma (35 ears), we investigated the history of otitis media and the incidence of complications involving the upper respiratory tract.The lipid peroxide concentration in the pooled fluid in the mastoid antrum was measured by a free radical reaction.The temporal bone pathologic anatomy in two ears affected by cholesterol granuloma was evaluated during autopsy.The history of otitis media included acute repetitive purulent otitis media in 76% and acute purulent otitis media in 18% inflammation of the upper respiratory tract was a complication in 73%. The lipid peroxide level was 17nmol/ml, which was 1.8 times higher than that in cases of otitis media with effusion.Since acute purulent otitis media is present in many cases of cholesterol granuloma, inflammation often remains in the mastoid antrum which is blocked.Recurrence of concealed otitis media may follow eustachitis resulting from infection of the upper respiratory tract. The mastoid air cells become narrow due to edematous mucosa resulting in negative pressure. Since the blood vessels within neogranulomas are weak, erythrocytes may exude.As the disease advances the effusion lacks ventilation and leukocytes engulf intiltrated inflammatory cells, releasing active oxygen. This destroys the erythrocytic membranes by hyperoxidation, resulting in lipids from the broken membrane and tissue fragments and cholesterol precipitation through clasmatosis.The proliferative mucosa in the effusion is replaced with granulation tissue and cholesterol granuloma slowly forms.