Posterior fossa neurenteric cysts can expand rapidly: case report.

Neurenteric cysts are considered congenital lesions that may slowly expand over time. Although more commonly found in the spinal canal, they may be found intracranially, particularly in the posterior fossa. Here, we present an unusual case of a large, rapidly expanding histologically confirmed posterior fossa neurenteric cyst in a 53-year-old woman, who presented with quadriparesis. Computed tomography imaging done ~1.5 years before admission failed to demonstrate any obvious abnormality; however, the lesion had grown to 4 cm in maximal dimension at presentation with significant mass effect. The lesion was resected microsurgically using a retrosigmoid approach. The patient improved postoperatively and was neurologically intact at last follow-up. We could find no other documented case of marked, rapid expansion of a neurenteric cyst in the literature. We conclude that, although neurenteric cysts are thought to be congenital, they can undergo rapid expansion even in adults. The mechanism of expansion is unknown but may involve increased secretion, hemorrhage, or inflammation. We discuss the surgical management and review the literature in view of this surprising finding.