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Dermoid of the petrous apex

Radioluccnt lesions of the petrous apex of the temporal bone are unusual, with an incidence of less than 1%. The differential diagnosis includes giant apical air cells, acquired cholesteatomas, congenital cholesteatomas or epidermoids, true dermoids and teratomas, and benign and malignant neoplasms. The authors present an extremely rare case of a true dermoid of the petrous apex which eroded into the clivus of the occipital bone, and discuss the differential diagnosis, symptomatology, and diagnostic work‐up.