The petrous temporal bone (including the cerebellopontine angle).

Lower resolution CT scanners play an important role in the evaluation of the cerebellopontine angle, but careful integration along with the older conventional examinations is often necessary. A high-resolution CT scanner may provide all the necessary information. With proper techniques, bony changes are most clearly analyzed, and small tumors of the acoustic nerve may be directly seen in the cerebellopontine angle, and even in the internal auditory canal, with only a contrast-enhanced scan. If necessary CT-air cisternography provides the most sensitive and least morbid of the definitive, invasive examinations. In scanning only a localized region, care must be taken not to overlook abnormalities just beyond the immediate cerebellopontine angle, either within the posterior fossa or the petrous temporal bone.