Neuroimaging features of neurenteric cysts: analysis of nine cases and review of the literature.

PURPOSE To gain a better understanding of neurenteric (NE) cysts via correlation of imaging findings and surgical and pathologic data. METHODS The medical records, imaging studies, surgical information, and pathologic material were retrospectively reviewed in nine patients with NE cysts, including seven proved and two very probable cases. RESULTS NE cysts occurred in the cerebellopontine angle in one case and extended from the cerebellopontine angle to the C2 level in a second. In the latter patient and the remaining seven with intraspinal lesions, the NE cyst was always located anterior to the spinal cord. The most common myelographic and CT myelographic appearance was that of a lobulated intradural extramedullary (IDEM) mass. Two patients had an intramedullary NE cyst with a somewhat unusual appearing exophytic IDEM-appearing expansion that can be a characteristic feature of these lesions. MR imaging demonstrated the NE cyst to be isointense to hyperintense relative to cerebrospinal fluid on long TR sequences and isointense or slightly hyperintense to cerebrospinal fluid on T1-weighted images. These signal characteristics correlate with the high-protein-content fluid within the cysts, usually described at surgery as milky or mucinous in character. CONCLUSION The diagnosis of NE cyst should be considered when imaging studies reveal the presence of a lobulated IDEM or an exophytic intramedullary cystic mass, especially in association with anterior spina bifida or other vertebral anomalies. MR can uniquely confirm the cystic nature of these masses and is the method of choice for their imaging investigation. Because cyst recurrence can occur, MR should also be used for long-term patient follow-up.