A case of primary mastoid cholesterol cyst

Abstract

A case with a primary mastoid cholesterol cyst accompanying massive bone destruction is reported. The patient was a 43-year-old male, who visited our clinic because of vertigo. Otoneurological examination revealed the patient's hearing and vestibular function to be nearly normal. A temporal bone CT showed a soft tissue mass in the left mastoid with large bone defects in the posterior and middle cranial fossae, and fistulas in all of the semicircular canals. MRI revealed a huge mass in the mastoid cavity apparently compressing the temporal lobe of the brain. The patient refused surgical treatment, and during the subsequent 4 year follow-up period the mass developed further and a cholesterol cyst was suspected based on the results of another MRI. Surgery revealed a huge cholesterol cyst located in the mastoid cavity with large bone defects and an exposed dura. Histological examination showed cholesterol granuloma accompanied by inflammation and bleeding and surrounded by thick scar tissue. Obstructive and persistent inflammation in the mastoid was considered to be related to development of the mastoid cholesterol cyst.