Malformations of the central nervous system in trisomy 18 syndrome

Malformations of the central nervous system in trisomy 18 are relatively uncommon as compared with trisomy 13 (D 1), but may nevertheless be part of the phenotypic manifestation of trisomy 18. Anomalies of the central nervous system observed in trisomy 18 have included: meningoencephalocele, hydrocephalus, prosencephaly, absent corpus callosum, defective falx cerebri, and abnormal cerebellum. A lumbar meningocele was observed in two infants described here, in one of whom there was also a strikingly abnormal brain with malformed gyri, absent occipital lobe, and defective optic tracts. The malformations of the central nervous system observed in the trisomy 18 syndrome are reviewed and summarized in a table.