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Development of anencephaly and its variants
1Carnegie Laboratories of Embryology, University of California, Davis 95617.
The American Journal of Anatomy
|March 1, 1991
Summary
Two human embryos with extreme anencephaly reveal insights into skull-brain development. Findings suggest skeletal defects may precede nervous system issues, impacting early embryonic development.
Area of Science:
- Developmental Biology
- Human Embryology
- Teratology
Background:
- Anencephaly, a severe neural tube defect, presents extreme variations in human embryos.
- Understanding craniocerebral interrelationships and developmental timing is crucial for comprehending these anomalies.
Purpose of the Study:
- To investigate extreme variants of anencephaly in human embryos.
- To elucidate the relationship between skull and brain development in early human embryogenesis.
- To determine the primary cause and timing of maldevelopment in anencephaly.
Main Methods:
- Comparative analysis of two human embryos (stage 22/54 days) exhibiting extreme anencephaly.
- Examination of chondrocranium and brain preservation in both embryos.
- Comparison with experimental data on embryonic development.
Main Results:
- Embryo X displayed a holoacranial skull with a well-preserved brain, showing comparable neural tracts to controls.
- Embryo Y exhibited a more normal chondrocranium (meroacranial precursor) but a completely degenerated brain.
- A dissociation between skull and brain development was observed, suggesting primary skeletal defects.
Conclusions:
- Skull and brain development may exhibit a degree of independence in anencephaly.
- Skeletal maldevelopment, particularly in paraxial mesenchyme, appears to be the primary issue, with nervous system effects being secondary.
- The mesenchymal defect likely originates early, around stages 8-9 (18-20 days), coinciding with neural tube closure failures.