Selected clinical research involving the central nervous system.

This paper updates three clinical research projects involving the central nervous system. Discussions of conditions with encephalocele include several associations: encephalocele/craniostenosis, transsphenoidal encephalocele/hypothalamic-pituitary dysfunction, encephalocele/oculo-auriculo-vertebral spectrum, and encephalocele/frontonasal dysplasia. The relationship between oculo-auriculo-vetebral spectrum with encephalocele and frontonasal dysplasia with epibulbar dermoids and ear tags is also discussed and an explanation for encephalocele formation in the Apert syndrome is provided. Studies of the central nervous system in Apert syndrome indicate that distortion ventriculomegaly is common, but progressive hydrocephalus occurs infrequently. A recurrent pattern of abnormalities was discerned consisting of megalencephaly, gyral abnormalities, and defects of the corpus callosum and limbic structures. Five neuropathologic studies lend further support to this pattern of CNS anomalies in the Apert syndrome. In a study of holoprosencephaly, eight principles governing associated facial dysmorphism were derived. Each diagnostic category was shown to have its own frequency and range of holoprosencephalic faces. Some categories, such as del(13q), have narrow ranges; others, such as trisomy 13 syndrome, have broad ranges. However, no broad diagnostic range is known to include agnathia-holoprosencephaly and other severe forms of facial dysmorphism without agnathia. Absent maxillary incisors and a single maxillary central incisor are extremely common in holoprosencephaly with severe facial dysmorphism and may occur on occasion as a striking microform of holoprosencephaly, most commonly in the autosomal dominant form.