Risk factors for epilepsy in children with posterior fossa malformations (PFM) were studied in 22 cases of PFM with epilepsy (41%), and 32 without epilepsy (59%), seen at the University of Bologna, Italy. The most common PFMs were cerebellar hypoplasia (43%), Dandy-Walker (D-W) complex (37%), and Arnold-Chiari (A-C) malformation (13%). Epilepsy recurred most frequently in A-C malformation (71%), compared to 35% in D-W complex, and 35% in cerebellar hypoplasia. Risk factors for epilepsy in PFM cases were cerebellar lesions plus familial antecendents for epilepsy and/or febrile convulsions; 50% in PFM cases with epilepsy, and 9% in PFM without epilepsy. Epilepsy was mainly partial in 77%; benign epilepsies and febrile convulsions occurred in 27%. 
COMMENT. Epilepsy may occur in 40% of children with posterior fossa malformation. A family history of epilepsy and/or febrile convulsions are significant risk factors for epilepsy in children with posterior fossa malformation.
Posterior fossa pathology other than malformation can predispose to epilepsy. Among 291 children treated for intracranial tumor at the Mayo Clinic over a 10 year period, seizures occurred in 17% - in 25% of patients with supratentorial tumors and in 12% of those with infratentorial tumors. The diagnosis of supratentorial tumors was delayed for an average of 2 years, whereas infratentorial tumors were diagnosed within 3 months of the initial seizure.