Massive Mastoid Cyst that Developed in the Middle Cranial Fossa

Abstract

This is a case report of a massive mastoid cyst that developed in the middle cranial fossa. The patient was a 69-year-old female, who visited the Dept. of Neurology because of a headache that persisted for several months. At the initial examination, a perforation of the right tympanic membrane and mixed hearing loss were observed, but no other neurological symptoms were detected. This patient had not undergone and kind of surgery for the middle ear. CT scan depicted a ring-enhanced lesion of the right middle cranial fossa. Ti and T2 MRIs depicted a highly intensive lesion starting from the mastoid cells. Therefore, intra-cranial development of a cholesterol cyst from the mastoid cavity was surmised. Surgery was performed using a combined transmastoid and middle cranial fossa approach. The cyst had developed to the middle cranial fossa from the mastoid cavity through the tegmen of the mastoid antrum. Pathological findings showed characteristics of a cholesterol cyst. We also discuss the developmental process of mastoid cyst as related to mastoid air cells development.