Introduction: Intracranial dermoid cysts are benign lesions derived from the embryonic ectoderm, compromising of less than 1% of all pediatric CNS tumors. Though rare, if missed and untreated prognosis can be grave. We describe a case of dermoid cyst presenting with obstructive hydrocephalus

Methods: Case report

Case description: 19-month-old boy was evaluated for developmental delay and eye blinking episodes that started at four months of age. Past medical history included ASD (Autism spectrum disorder) and GERD (Gastro esophageal reflux disease). Family reported recurrent fevers during the last year that had been attributed to respiratory infections. He had also been diagnosed with milk and egg allergies, but symptoms did not subside with their cessation. Vomiting was attributed to GERD, however, persisted despite treatment with proton pump inhibitors. Neurological examination was non- focal.Given the nonspecific history and physical examination findings, differential diagnosis was broad, and an extensive workup was initiated. Testing for infectious, metabolic, and genetic disorders was unremarkable.

Results: Imaging revealed obstructive hydrocephalus due to a posterior fossa mass with peripheral enhancement centered in the left cerebellar peduncle. There was a non- enhancing lesion extending to skull with a sinus tract to the skin.

He underwent posterior fossa craniotomy with resection of sinus tract and mass. Pathology from resection was consistent with dermoid cyst with evidence of prior rupture and abscess formation.

Conclusion: This rare case of dermoid cyst presenting as vomiting underscores the significance of considering neurological tumors as cause of unrelenting gastro intestinal symptoms.