Epidemiology of Infratentorial Ependymomas in Children
Incidence and Prevalence
10–20% of posterior fossa tumors: Infratentorial ependymomas comprise 10–20% of all posterior fossa tumors (2).
Peak incidence in young children: Intracranial infratentorial ependymomas have a bimodal age distribution in children, with the first peak being in the age group under 5 years.
Greater proportion of posterior fossa tumors: Infratentorial ependymomas comprise 30% of posterior fossa tumors in children younger than 3 years of age but only 10–20% of posterior fossa tumors in the overall pediatric population (2).
Males 2 to 1: Males are affected about twice as often as females (2).
Viral infection: Viral etiology is proposed due to the presence of DNA sequences identical to segments of the SV 40 virus in childhood infratentorial ependymomas (3).
Genetic predisposition: Molecular genetic analysis of some children with infratentorial ependymomas shows allelic losses on chromosome 22q, DNA losses on chromosome 17p and chromosome 1p losses. Mutations in the p53 tumor suppressor gene have not been identified in infratentorial ependymomas (4, 5).
Relationships to Other Disease States
NF2: Infratentorial ependymomas can occasionally be seen in association with NF2 but generally do not occur in association with other disease states (6).