Abnormal Sylvian fissure on prenatal cerebral imaging: significance and correlation with neuropathological and postnatal data.

OBJECTIVE: To illustrate and determine the significance of abnormal Sylvian fissure development (or abnormal operculization) in cases in which prenatal cerebral imaging is suggestive of underlying cortical dysplasia.
METHODS: This was a retrospective study of 15 fetuses at 24-34 weeks in which abnormal operculization was identified on prenatal cerebral imaging and for which follow-up data were available. The imaging findings were correlated to macro- and microscopic neuropathological data (n = 11) or to postnatal clinical and imaging findings (n = 4).
RESULTS: On microscopic examination of fetuses from 11 terminated pregnancies, abnormal operculization was associated with cortical dysplasia in four cases and the cortex was normal in seven. Abnormal operculization was associated with cortical dysplasia in only one of the four liveborn infants. Cases of abnormal Sylvian fissure development with normal cortical architecture were classified, according to associated anomalies of the central nervous system, into one of five groups: those with neural tube defects, microcephaly or frontal hypoplasia, glutaric aciduria, other cerebral abnormalities, and extracerebral anomalies.
CONCLUSION: Abnormal operculization on prenatal imaging does not systematically reflect underlying cortical dysplasia. It may be related to extracortical factors such as abnormal cerebral volume or other developmental anomalies of the central nervous system. An understanding of the significance of abnormal Sylvian fissure development could be useful in integrating its analysis into a more general one of the whole central nervous system.