Cerebellar Enterogenous Cyst with Atypical Appearance and Pathological Findings.

Background: Intracranial enterogenous cysts are rare and occur mainly in the posterior fossa. These cysts are usually extra-axial, midline, anterior to the brainstem, or at the cerebellopontine angle. Intracranial intra-axial enterogenous cysts are extremely rare. We report a case of an intra-axial cerebellar enterogenous cyst in which diagnosis was difficult because the lesion resembled an arachnoid cyst in appearance and showed atypical pathologic findings.

Case Description: A 69-year-old woman had a 2-year history of progressive headache, giddiness, and unsteadiness of gait. Magnetic resonance imaging showed a cystic lesion with isointensity to cerebrospinal fluid in the left cerebellar hemisphere, reaching into the fourth ventricle. The patient underwent fenestration of the cyst and creation of a communication between the fourth ventricle and cyst because the tight attachment of the cyst wall to the cerebellum prevented total removal of the cyst. Although pathologic examinations did not show findings typical of enterogenous cyst, the diagnosis was finally made based on the presence of basement membrane and immunohistochemical results.

Conclusion: The diagnosis of enterogenous cyst is based mainly on histologic findings, because characteristic findings on neuroimaging have not been defined. Although total resection of enterogenous cysts is recommended in general, partial resection while ensuring the cyst communicates adequately with the surrounding cerebrospinal fluid space with or without a shunt procedure may be useful if the cyst is adherent to surrounding neurovascular structures.