Posterior fossa dermoid cyst with sinus tract and meningitis in a toddler.

Intracranial dermoid cysts are rare, but can cause recurrent bacterial or aseptic meningitis, abscesses or mass effect. We describe a toddler who manifested an occipital "lump" for 6 months without further evaluation. He presented with lethargy and meningitis. A posterior fossa dermoid cyst with a sinus tract was detected by imaging studies. He underwent prompt surgical excision of the cyst and the sinus, and received a prolonged course of antibiotics, because anaerobes were isolated from the contents of the cyst and blood. His postoperative course was complicated, and required the placement of a lumboperitoneal shunt. A high index of suspicion for the detection of dermoid cysts is required when a congenital midline skin lesion such as a dimple or a scalp swelling is reported. Prophylactic excision is indicated to prevent serious sequelae.