Trapped Fourth Ventricle in a Pediatric Patient With a History of Post-Traumatic Hydrocephalus and Ventriculoperitoneal Shunt: A Case Report and Literature Review.

Trapped fourth ventricle (TFV) is a rare, serious complication of ventriculoperitoneal (VP) shunting that can mimic posterior fossa tumors and cause life-threatening brainstem compression. We report the case of a 7-year-old boy with a history of a VP shunt for post-traumatic hydrocephalus who presented with progressive drowsiness and gait disturbances. While initial CT imaging suggested a tumor, subsequent MRI confirmed a markedly dilated fourth ventricle, diagnosing TFV. The patient underwent open posterior fenestration with microsurgical arachnoid adhesiolysis, which successfully restored cerebrospinal fluid dynamics. This intervention resulted in the complete resolution of his neurological symptoms at 1-month follow-up. This case highlights the importance of suspecting TFV in shunted patients with new neurological deficits and demonstrates that open fenestration is a highly effective treatment strategy, particularly when dense adhesions are clinically suspected. Timely diagnosis with advanced imaging and prompt surgical intervention are crucial to prevent irreversible damage and ensure favorable neurological outcomes.