Early recurrence of a pediatric high cervical neurenteric cyst mimicking an arachnoid cyst following cyst fenestration.

Background: Neurenteric cysts (NCs) are rare congenital cystic lesions accounting for approximately 0.3-1.3% of spinal tumors. Although uncommon in children, cervical NCs can cause rapid spinal cord compression. Recurrence after incomplete resection has been well documented; however, the fact that these lesions resemble arachnoid cysts and the timing of recurrence have not been sufficiently emphasized. Case Description: A 2-year-old boy presented with rapidly progressive neurological deterioration over 2 weeks, progressing from occipital pain to quadriplegia. Magnetic resonance imaging (MRI) revealed a ventrally located intradural extramedullary cystic lesion at the C2/3 level with cerebrospinal fluid-equivalent signal intensity on both T1- and T2-weighted images, for which an arachnoid cyst was considered in the differential diagnosis. Emergency surgery through a posterolateral approach was performed, and cyst fenestration resulted in immediate neurological improvement. However, the cyst recurred within only 3 weeks after surgery, leading to rapid re-aggravation of quadriplegia. A second emergency operation was therefore undertaken, during which the cyst wall was resected as extensively as possible. The patient achieved complete neurological recovery, and follow-up MRI confirmed complete resolution of the cyst. No recurrence was observed during a 3-year follow-up period. Conclusion: This case highlights that pediatric cervical NCs may closely mimic arachnoid cysts on imaging, potentially leading to insufficient surgical management if misdiagnosed. Although cyst fenestration alone may provide temporary neurological improvement, it carries a risk of recurrence. Therefore, initial maximal safe resection of the cyst wall is essential to minimize recurrence and to achieve durable long-term neurological outcomes.