Reverse brain herniation following CSF diversion in a 2-year-old child-case report and review of literature.

Reverse brain herniation (RBH) is a rare but catastrophic complication following cerebrospinal fluid (CSF) diversion in patients with posterior fossa tumours associated with obstructive hydrocephalus. It carries high mortality and remains underreported. The role of preoperative CSF diversion in such cases continues to be controversial. We report a case of a 2-year-old female with a fourth ventricular tumour presenting with acute decompensated obstructive hydrocephalus who underwent emergency ventriculoperitoneal (VP) shunt placement. Postoperatively, the patient failed to show neurological improvement, and imaging revealed features consistent with reverse brain herniation. She underwent urgent posterior fossa decompression with tumour excision within 6 h, resulting in gradual neurological recovery. Histopathology confirmed CNS WHO Grade III ependymoma. The patient later developed tumour recurrence requiring re-excision and is currently undergoing adjuvant radiotherapy. This case underscores the importance of vigilant postoperative monitoring following CSF diversion in posterior fossa tumours and highlights that early recognition and prompt surgical intervention can significantly improve outcomes in this otherwise highly fatal condition.