MR OF THE CEREBRAL OPERCULUM - ABNORMAL OPERCULAR FORMATION IN INFANTS AND CHILDREN

PURPOSE: To evaluate abnormalities of the cerebral operculum in infant s and children and to propose the embryogenic basis of abnormal opercu lar formation as determined from MR imaging findings. METHODS: Eighty- six infants and children who had abnormally wide interopercular distan ces and/or distorted opercular topography seen on MR images were studi ed retrospectively. Clinically, patients presented with tonal abnormal ities, macrocephaly, microcephaly, seizures, developmental delay, cere bral palsy, or facial dysmorphism. The abnormal opercula were compared with developing opercula at different stages of gestation. RESULTS: A mong the 86 infants and children, two categories of opercular abnormal ities were identified: an underdeveloped operculum (n = 64) and a malf ormed operculum (n = 22). The malformed operculum was further classifi ed into three subtypes: nonformation of the operculum with lissencepha ly (n = 1, 1%), abnormal opercular formation with pachygyria (n = 11, 13%), and nonformation or abnormal Formation of the operculum without pachygyria or lissencephaly (n = 10, 12%). Two subtypes of the underde veloped operculum were identified: an open operculum without a normal insula (n = 6, 7%) and an open operculum with a normal insula (n = 58, 67%), The five subtypes of abnormal opercular configuration showed a range of maturity that was comparable to the developing operculum at d ifferent ages. CONCLUSION: Opercular anomalies appear to follow sequen tially predetermined normal steps in development, Arrest in opercular development or malformation may occur after an initial insult. MR imag ing is the method of choice by which to identify these abnormalities.