Cholesterol granuloma involving the temporal bone.

The cholesterol granuloma does not represent an independent clinical or pathological entity, rather it is a term used for the description of a tissue response of the temporal bone, to the presence of a particular foreign body, i.e., cholesterol crystals. Three factors are considered to play an important role in its development: 1) interference with drainage, 2) hemorrhage, and 3) obstruction of ventilation. The cause of the initial hemorrhage may be a hemorrhagic inflammation or diathesis, a trauma or some other form of vascular disorder. Interference with air exchange and clearance can be caused by: tubal blockage, persistent mesenchyme, polypoid changes, scar formations, tympanosclerosis, cholesteatoma, etc. The cholesterol granuloma may develop in any portion of the pneumatic system of the temporal bone and it can be associated with a variety of middle ear disorders. Its principal precursor is the chronic middle ear effusion or serous otitis media. Its clinical expression and hallmark is the "idiopathic hemototympanum," the dark bluish discoloration of the tympanic membrane. Osteitis and bone erosion are manifestations of an unusual, more advanced stage. Resorption of bone, in a rare instance, may lead to extensive destruction of the temporal bone.