Diagnostic and surgical implications of ventral vertebrobasilar displacement by posterior fossa neurenteric cysts.

OBJECTIVE: Neurenteric cysts (NECs) are uncommonly encountered lesions of the central nervous system with heterogeneous imaging characteristics. The object of this study was to review the preoperative imaging findings represented among a cohort of surgically treated posterior fossa NECs. These findings are considered in the context of surgical technique, and inform an understanding of aberrant neuroembryological development associated with NECs.

METHODS: A single-institution, multisurgeon series of 7 consecutive patients (5 female and 2 male patients, mean age 36 years, range 19 to 57 years) treated surgically for histopathologically confirmed posterior fossa NECs was retrospectively reviewed. Lesion imaging and anatomic characteristics were noted on preoperative magnetic resonance imaging (MRI). Imaging comparisons were made against an additional cohort of 266 consecutive surgically treated posterior fossa masses to validate unique anatomic findings.

RESULTS: T1 and T2 MRI signal characteristics were variable when compared across lesions. All NECs were found to be anteriorly located within the posterior fossa, but always situated between the brainstem pial surface and the vertebrobasilar system, causing ventral displacement of vertebrobasilar vessels.

CONCLUSIONS: Posterior fossa NECs display variable patterns of MRI signal and are commonly considered as part of a broad differential of cystic posterior fossa masses. We identified tumor insinuation between the ventral brainstem and vertebrobasilar system as a highly sensitive and specific radiographic sign for NECs. This finding was not observed among a large cohort of posterior fossa masses representative of other multiple pathologies.