Cerebellopontine angle endodermal cyst presenting with hemifacial spasm.

Intracranial endodermal cysts presenting with hemifacial spasm (HFS) are extremely rare. We report a right cerebellopontine angle (CPA) endodermal cyst in a 56-year-old man who presented with a 6-month history of right-sided hemifacial spasm. Computed tomography revealed a homogenous, well-demarcated, hyperdense lesion extending from prepontine cistern to right CPA. Magnetic resonance imaging demonstrated a right CPA extra-axial cystic lesion protruding into Meckel's cave, with compression of cranial nerves VII and VIII. Light brown, creamy cystic content was totally removed, and the thin cyst wall surrounding cranial nerves VII and VIII and the right vertebral artery was subtotally removed through the right lateral suboccipital approach. On microscopic examination, the cyst wall was composed of mono- to multilayered stratified epithelia, which were lined by ciliated or nonciliated cuboidal cells, with cilia showing the characteristic 9 + 2 pattern. Immunohistochemistry showed positive staining of cells composing the cyst wall with carcinoembryonic antigen, epithelial membrane antigen, cytokeratin 8, and negative staining with cytokeratin 20, and S-100, thereby characterizing endodermal cyst. Postoperatively, the patient was free of facial spasm.