J Korean Neurosurg Soc.  2021 May;64(3):329-339. 10.3340/jkns.2020.0125.

Gastrulation : Current Concepts and Implications for Spinal Malformations

• Thompson DNP

• KMID: 2515488
• DOI: http://doi.org/10.3340/jkns.2020.0125

Abstract

It has been recognised for over a century that the events of gastrulation are fundamental in determining, not only the development of the neuraxis but the organisation of the entire primitive embryo. Until recently our understanding of gastrulation was based on detailed histological analysis in animal models and relatively rare human tissue preparations from aborted fetuses. Such studies resulted in a model of gastrulation that neurosurgeons have subsequently used as a means of trying to explain some of the congenital anomalies of caudal spinal cord and vertebral development that present in paediatric neurosurgical practice. Recent advances in developmental biology, in particular cellular biology and molecular genetics have offered new insights into very early development. Understanding the processes that underlie cellular interactions, gene expression and activation/inhibition of signalling pathways has changed the way embryologists view gastrulation and this has led to a shift in emphasis from the ‘descriptive and morphological’ to the ‘mechanistic and functional’. Unfortunately, thus far it has proved difficult to translate this improved knowledge of normal development, typically derived from non-human models, into an understanding of the mechanisms underlying human malformations such as the spinal dysraphisms and anomalies of caudal development. A paediatric neurosurgeons perspective of current concepts in gastrulation is presented along with a critical review of the current hypotheses of human malformations that have been attributed to disorders of this stage of embryogenesis.

Keyword

Gastrulation; Notochord; Neurulation; Primitive streak; Spinal dysraphism

Figure

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  Fig. 1. Sagittal magnetic resonance imaging scan of 6 years old boy with neurenteric cyst. There is a vertebral malformation. There is cystic expansion of the spinal cord. At surgery the contents of the cyst were mucinous.

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  Fig. 2. Diagrams illustrating the putative endomesenchymal tract and its relationship to the formation of split cord malformations. Adapted from Pang et al.[21]. SCM : split cord malformation, POD : post ovulation day.

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  Fig. 3. Sagittal (A) and axial (B) magnetic resonance imaging scans of split cord malformation type 1. Vertebral malformation at L3 is shown with midline spur emanating from the posterior surface of the vertebral body and two hemichords.

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  Fig. 4. Sagittal magnetic resonance imaging scan of caudal regression syndrome. There is absence of the conus and agenesis of the sacral segments distal to S2.

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  Fig. 5. Sagittal magnetic resonance imaging scan in an infant with cloacal extrophy. There is a terminal myelocystocele with extensive spinal cord syrinx formation.

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  Fig. 6. Sagittal magnetic resonance imaging scan in a case of Currarino syndrome demonstrating a presacral cyst (long arrow) and low lying spinal cord (short arrow), there is sacral dysgensis. The child was born with imperforate anus.

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  Fig. 7. 3D computed tomography (A) and magnetic resonance imaging (B and C) scans of Pyopagus conjoined twins. There is no bony union but the two children have a conjoined spinal cord.

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