Congenital bony fixation of the malleus

Bony fixation of the malleus seems to be one of the most controversial clin ical entities among various congenital disorders of the auditory ossicles. According to various theories, it could be caused by trauma, chronic infect ion of the ear, otosclerosis or even development failures in the tympanic c avity itself. Histological analysis of 1,108 temporal bones showing a norma l middle ear structure was performed. All bones were cut in serial sections of 20 microns. Audiograms and the data on ear trauma or chronic infection were analysed from case histories belonging to each bony specimen. Bony fix ation of the malleus was found in 14 cases. It was almost always unilateral . The most frequent site of the fixation was the lateral epitympanal wall. The forms of fixation differed from a thin bony lamella to a solid bony bri dge. The mallear ligaments were not involved in any case. No relationship t o chronic ear infection, ear trauma or otosclerosis was found. Only a sligh t conductive hearing impairment up to 20 dB was recorded in 6 out of 14 cas es. The most probable predisposing anatomical factors for the onset of the bony fixation of the malleus and the most recent preoperative diagnostic po ssibilities are discussed.