Congenital Bilateral Perisylvian Syndrome (Bilateral
Opercular Syndrome): A structural malformation of the brain consisting of
polymicrogyria, i.e., the development of small and prominent convolutions separated by
shallow and enlarged sulci. MRI scan shows irregular thickening and a lumpy aspect of the
brain. Clinically characterized by paralysis of the face, tongue, and hypopharynx, with
dysarthria and severe drooling. Most patients present seizures (onset age is 4 to 12
years; seizures are poorly controlled in 60% of cases) and severe cognitive deficit.
Most seizures are atypical absences, tonic or atonic drop attacks. Tonic-clonic
seizures (e.g., Lennox-Gastaut syndrome) are also present. Arthrogryposis has been
described.