[Aneurysmal cyst of the petrous bone. Apropos of a case].

Aneurysmal bone cyst (ABC) is a rare form of osseous dystrophy. A lesion of the petrous temporal bone appears to be extremely rare. It must be differentiated from a hemangioma which is a hamartoma affecting the geniculate ganglion or the internal auditory meatus. The case described involved a 23-year-old woman. The ABC presented with violent otalgia and severe endolabyrinthic-type perception deafness. It was associated with extensive bony destruction of the petrous temporal and occipital bones. Curettage only led to considerable through temporary regression of deafness and bone reconstruction within a few months. Thrombosis of the internal jugular, confirmed at operation, is an interesting contribution in terms of the pathogenesis of ABC, apparently linked to disturbances of venous pressure. Surveillance is required since this benign condition may be recur.