Related Experiment Videos
Experimentally induced Chiari-like malformation with myeloschisis in chick embryos
Insights
Surgically induced myeloschisis in chick embryos led to Chiari malformation-like changes, suggesting a direct causal link. This supports cerebrospinal fluid dynamics as the primary cause, not neural or mesenchymal factors.
Area of Science:
- Developmental Biology
- Neuroscience
- Teratology
Background:
- The frequent co-occurrence of Chiari malformation and hydrocephalus with myeloschisis has been observed, but pathogenetic theories remain incomplete.
- Existing theories struggle to explain all facets of this complex disorder.
Purpose of the Study:
- To investigate the causal relationship between surgically induced myeloschisis and the development of Chiari malformation and hydrocephalus.
- To determine if myeloschisis directly causes these conditions or if they share a common underlying cause.
Main Methods:
- Surgically induced myeloschisis in Hamburger and Hamilton stage 16-19 chick embryos by opening the neural tube.
- Embryos were divided into cervicothoracic and lumbosacral groups and re-incubated until postoperative day 11.
- Morphological analysis of the posterior cranial fossa and its components via sagittal plane sectioning and light microscopy.
Main Results:
- Myeloschisis was induced in 100% of operated embryos.
- Embryos with myeloschisis exhibited smaller fourth ventricles and narrower posterior cranial fossa subarachnoid spaces compared to controls.
- Downward cerebellar displacement, characteristic of Chiari malformation, was observed in severe cases, though hydrocephalus was absent.
Conclusions:
- Surgically induced myeloschisis in chick embryos mimics morphological changes of Chiari malformation.
- These findings strongly suggest a direct causal relationship between myeloschisis and Chiari malformation.
- The results support pathogenetic theories implicating cerebrospinal fluid dynamics disturbances over primary mesenchymal or neural origins.
Abstract:
Though several pathogenetic theories concerning the frequent association of Chiari malformation and hydrocephalus with myeloschisis have been suggested, none of them explains all the aspects of the disorder. To investigate whether myeloschisis is the direct cause of Chiari malformation and hydrocephalus or these conditions are the results of another basic event, we observed the morphological changes of the posterior cranial fossa and its components in the chick embryos with surgically induced myeloschisis. To make myeloschistic lesions, we opened the neural tube for a length of 9-11 somites in Hamburger and Hamilton stage 16-19 chick embryos. They were divided into cervicothoracic (C-T) and lumbosacral(L-S) groups according to the area of incision. The embryos were re-incubated until postoperative day 11. In the control group, embryos were incubated with the eggshell window open as their experimental counterparts. The survival rates of each group were as follows; 11% (9 survivors/85 operated embryos), 8% (7/83), and 17% (10/60) in the C-T, L-S and control groups, respectively. Myeloschisis positive rates were 100% in the operated groups and 0% in the control group. The heads of embryos were sectioned along the sagittal plane to observe the morphological changes in the posterior cranial fossa and its components. Of the survivors, five in the C-T group, two in the L-S group and six in the control group were available for light microscopic inspection. In the majority of embryos with myeloschisis, without difference between the C-T and L-S groups, the fourth ventricles were smaller than those of the control group and the subarachnoid spaces in the posterior cranial fossa were also narrower. In embryos with severe changes, the cerebellum displaced downward comparing with that of the control embryos. No evidence of hydrocephalus was present Though not always typical, morphological changes similar to Chiari malformation were observed in chick embryos with surgically induced myeloschisis. It suggests a strong direct causal relationship between the two conditions and supports the theories of derangements in cerebrospinal fluid dynamics rather than those of primary mesenchymal or neural origin as a pathogenetic mechanism of Chiari malformation.