Neural tube
and folate

The BRAIN magazine

Pregnant woman holding up a small ultrasound of her baby

The human central nervous system (the brain and spinal cord) contains around 100 billion neurons distributed between four main areas: the forebrain, midbrain, hindbrain and spinal cord. A fascinating question immediately arises: what are the embryonic origins of such a complex organ?

We now know that the central nervous system begins as a simple sheet of cells, called the neural plate, on the dorsal surface (think the dorsal fin of a shark) of the very young embryo three weeks after conception.

Scan of a developing baby in the womb showing the neural tube which runs from the brain to the end of the spine

Developing baby with the neural tube highlighted. Image: TheVisualMD / Science Source

Developing baby with the neural tube highlighted. Image: Science Source

Between four and six weeks, the neural plate lengthens along the entire head-to-tail axis of the growing embryo. The plate’s edges curl upwards and fuse to form the neural tube, a cylinder comprising stem cells that eventually produce all cells in the central nervous system.

Failure of the neural tube to fuse lengthways can result in devastating conditions, such as anencephaly, where the neural tissue bulges from the brain, or spina bifida, where the end of the spinal cord remains open.

A diagram of the neural tube of a developing foetus at 3 and 4 weeks after conception

Between four and six weeks after conception, the neural plate lengthens along the entire head-to-tail axis of the growing embryo (1). Then, the neural plate begins to fold and fuse at the tips (2) to form the neural tube (3). The neural tube contains the neural stem cells that produce all cells in the central nervous system. About 1/1000 pregnancies has a neural tube defect, commonly spina bifida or anencephaly. Taking B vitamin folate reduces the incidence of neural tube defects. Image: Dr Belal Shohayeb, Queensland Brain Institute

Between four and six weeks after conception, the neural plate lengthens along the entire head-to-tail axis of the growing embryo (1). Then, the neural plate begins to fold and fuse at the tips (2) to form the neural tube (3). The neural tube contains the neural stem cells that produce all cells in the central nervous system. About 1/1000 pregnancies has a neural tube defect, commonly spina bifida or anencephaly. Taking B vitamin folate reduces the incidence of neural tube defects. Image: Dr Belal Shohayeb, Queensland Brain Institute

Neural tube defects occur frequently in the population (~1/1000 pregnancies). The introduction of B vitamin folate, an important ingredient in the production of key metabolic molecules, into the diet of pregnant mothers and women of childbearing age greatly reduces the risk.