Endodermal cyst of the quadrigeminal cistern: case report.

Background: Endodermal cysts usually develop in the subdural space in the anterior spinal cord and rarely occur inside the cranium. Most intracranial endodermal cysts develop in the posterior fossa. We report the first case of an endodermal cyst in the quadrigeminal cistern.
Case Description: The patient was a 71-year-old man who suffered from gait disturbance for 6 months. Although head computed tomography (CT) scanning 4 years previously did not show any cystic lesion, CT and magnetic resonance imaging (MRI) on admission showed a cystic lesion extending from the quadrigeminal cistern to the right ambient cistern. The cyst was subtotally removed via a suboccipital transtentorial approach. The cyst wall consisted of a layer of columnar epithelium and connective tissue. Based on the results of immunostaining, it was diagnosed as an endodermal cyst.
Conclusions: It is possible that the increase of secretion from the cells lining the cyst may have caused a difference in osmotic pressure between the cerebrospinal fluid and the cyst contents, leading to rapid enlargement of the cyst. An endodermal cyst should be removed as completely as possible because its cells have the ability to grow and produce secretions.