A case of cholesterol granuloma extending to the infratemporal fossa treated by transtympanic fenestration of the cyst

We report a rare case of a patient with a cholesterol granuloma located in the infratemporal fossa. A 68-year-old male patient was referred to our department because of the findings on CT at another hospital of right ear opacification and bone defect of the anterior wall of the tympanum. He had undergone right ear surgery at the age of 33 years. He had suffered from hearing loss on the right side for many years and experienced right-sided otorrhea since two months before presentation. In addition, a lesion in the anterior wall of the right maxillary sinus associated with a bone defect was also recognized on the CT. MRI demonstrated a large cystic lesion extending to the infratemporal fossa and tympanum. Cholesterol granuloma, cholesteatoma, and tumor invasion from the maxillary sinus were considered in the differential diagnosis; OMAAV, or Otitis Media with Anti-neutrophil Cytoplasmic Antibody (ANCA)-associated vasculitis, was also suspected because blood examination revealed an elevated myeloperoxidase-ANCA titer. Tympanoplasty was planned for biopsy and drainage of the cyst, followed by endoscopic sinus surgery for biopsy. Canal walldown mastoidectomy was performed, the granulation tissue occupying the tympanum and attic was removed, and the bone defect was found above the orifice of the right Eustachian tube. After fenestration, abundant brown fluid flowed out of the cavity in the infratemporal fossa. A drainage tube was then inserted into the tympanic membrane and a silicone sheet into the cavity of the infratemporal fossa. Histological examination demonstrated no evidence of malignant tumor or OMAAV, whereas the finding of a granuloma containing cholesterol crystals in the middle ear mucosa indicated the diagnosis of cholesterol granuloma. After the surgery, the otorrhea resolved. The patient is under follow-up at our hospital and has shown no evidence of recurrence since the surgery.