Cerebello-pontine angle epidermoid cyst, with special reference to metrizamide CT cisternographic findings suggesting communication of the cyst with the subarachnoid space

A case of left C-P angle epidermoid cyst with possible communication with the subarachnoid space based on the findings of metrizamide CT cisternography, RI cisternography and surgery, is described. A 46-year-old female was admitted due to left hemifacial spasm, ringing and loss of auditory of the left ear, and gait disturbance of over ten years' duration. CT-scan revealed a large low density area in the posterior fossa (+4 to +5 Hounsfield units) with partial capsular enhancement. On metrizamide CT cisternography, a bizarre-shaped area of high density appeared within the confines of the low density area at 1 hour after intrathecal injection of metrizamide and persisted for hours. This suggested metrizamide penetration from the subarachnoid space into the cyst through the capsule. RI cisternography revealed definitely increased RI uptake into the cyst in the same sequence as the metrizamide CT cisternography. Following left suboccipital craniectomy, a cystic pearly tumor was noted beneath the left cerebellar hemisphere. Its thin capsule was in contact with the distended cisterna magna. Following aspiration of the cyst fluid, the distended cisterna magna collapsed synchronously. These findings, including those of metrizamide CT and RI cisternography, clearly suggested the existence of communication of fluid between the epidermoid cyst and subarachnoid space. Histological examination confirmed epidermoid cyst. (author)