Management of a congenital arachnoid cyst in a newborn with obstructive hydrocephalus: A multistage surgical approach and neurodevelopmental outcome.

Background: Arachnoid cysts (ACs) are cerebrospinal fluid-filled lesions of uncertain etiology, occasionally associated with other congenital malformations. While many remain asymptomatic, large or expanding cysts can cause hydrocephalus and neurological compromise, warranting intervention. Optimal management strategies for newborns with complex cyst anatomy remain debated, especially when initial fenestration fails. Case Description: We report the clinical course and surgical management of a full-term male newborn prenatally diagnosed with a large left frontoparietal AC, agenesis of the corpus callosum, and suspected schizencephalic changes. Postnatal imaging confirmed cyst-induced obstructive hydrocephalus. An initial endoscopic cystoventriculostomy was performed at 13 days of life, but neuroimaging showed persistent cyst growth and ventricular dilation. Two subsequent surgeries were required: A contralateral cystoventricular diversion and, finally, a cystoperitoneal shunt using stereotactic navigation and programmable valve implantation. Serial magnetic resonance imaging demonstrated progressive cyst size reduction and midline realignment. Postoperative anthropometric analysis showed normalization of head circumference growth curves. At 4 months, the infant showed a stable neurological status and improved psychomotor milestones. Conclusion: This case highlights the challenges of managing congenital ACs complicated by hydrocephalus, particularly when primary endoscopic fenestration fails. A staged, individualized neurosurgical approach, guided by neuroimaging and clinical evolution, can achieve both structural resolution and developmental stabilization. The use of stereotactic navigation and programmable shunt systems may enhance long-term outcomes in refractory neonatal cases.