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Fat-fluid level in intracranial epidermoid cyst.

A 31-year-old woman was seen in the ophthalmology department because of progressively diminishing vision of the right eye. There was a history of “sinus headaches” and chronic postnasal drip, but no recent increase in drainage and no tenderness or fever. The patient had been in an automobile accident during the past year but had not injured her head. At her first visit visual acuity on the right was 20/30, and small white areas were seen around the macula suggesting a diagnosis of serous retinopathy. After 2 months her visual acuity had deteriorated to 20/200, and a large central scotoma was found, resulting in the diagnosis of optic neuritis on compression. Electroencephalogram and nadionuclide brain scan were negative. Skull radiographs revealed a fluid level low and toward the left in the midfrontal region (fig. 1 ). Because this was thought to be an air-fluid level, polytomography of the skull base was performed; no break in the continuity of the bones was found. A CT scan again revealed a striking fluid level (fig. 2). The nadiolucent area above the level had EMI absorption values ranging from -30 to -70. These values are considerably higher than of air and consistent with a lipid substance. It was apparent that a fat-containing intracranial mass such as a lipoma. teratoma, denmoid, or epidermoid must be present. An angiognam demonstrated an avascular mass in the subfrontal region (fig. 3). A pneumoencephalognam revealed no communication between the ventricles or subanachnoid spaces and the mass. Through frontal craniotomy, a tense cystic mass was found covering the medial frontal fossa and extending into the interhemispheric fissure. It consisted of a caudad blue thin-walled pant and a craniad lemon yellow part. the anterior-inferior wall of which had a solid yellowish-white component. Aspiration from the craniad portion yielded an opalescent yellow oily material in which floated flecks of chalky material. The fluid clotted on standing. When the interior of the cyst was inspected, there was a gush of fluid with large globules resembling free fat floating on the surface. The volume of fluid in the cyst was 25-30 ml. The cyst wall was removed except for a segment on the left optic nerve which was laterally deviated and stretched 4-5 cm. The right optic nerve had been markedly compressed and was barely seen before the cyst was removed. The cyst fluid contamed cholesterol and triglycerides (181 mg/100 ml and 25 g/100 ml, respectively). Pathologic examination revealed an epidermoid cyst lined by squamous epithelium beneath which were areas of heaped up fat-containing cells. The patient’s visual acuity was normal at follow-up examination 2 months postoperatively.