Dermal sinus tract in occipital region

A three-year-old boy presented after two months of morning headache and intermittent vomiting. He was febrile and somnolent with dysconjugate gaze. Blood work showed a leukocytosis with 29,800 leukocytes/microL. Cranial computed tomography (A) revealed a bony tract in the midline occipital skull, suggesting the presence of a dermal sinus tract. Closer direct inspection of the skin revealed a dimple that was the sinus tract opening. Magnetic resonance imaging (B) revealed a large cystic enhancing posterior fossa mass with hydrocephalus. A ventriculostomy was placed, with cloudy cerebrospinal fluid (7575 leukocytes). Bacterial culture isolated Cutibacterium (formerly Propionibacterium) acnes. The patient underwent posterior fossa craniotomy with complete resection of the dermal sinus tract which led directly into the infected ruptured dermoid cyst.
(A) Sagittal noncontrast computed tomography with defect in occipital bone (arrow).
(B) Sagittal T₂ magnetic resonance imaging demonstrating the tract at the skin (arrowhead) and cystic lesion (infected dermoid cyst [arrow] associated with dermal sinus tract).