Epidermoid and cholesterol cysts in the apex of the petrous bone.

Cystic lesions in the petrous apex are nearly always either epidermoid cysts, with a soft but solid content, or cholesterol cysts, containing brown fluid. They may be symptomless, produce progressive cranial nerve palsies or, occasionally, reach the CSF pathways thus leading either to meningitis or a CSF leak. Thirteen cases and four unverified cases have been encountered amongst a series of more than 500 cerebellopontine angle tumours. Their clinical features, radiological diagnosis and difficulties of surgical approach are discussed.