Neural Tube Defects – Neurulation

by John McLachlan, PhD

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    00:00 So these varieties will have different effects depending on the level of which they occur.

    00:08 So there are also the types of defect as we’ve just seen in the previous slide, and this also will influence the outcome which arises from these conditions. For instance, in severe cases such as myelomeningocele, or even a completely open rachischisis, then we may observe paralysis or loss of function below the level of the defect and this may include bowel and bladder function, and of course in the end, severe cases will lead to death.

    00:37 So, what causes these neural tube defects? Well, we know that in a large number, perhaps 60 percent of cases, there is a genetic component. We know this partly because it seems to be regionally distributed. So for instance, Scotland and Ireland were sometimes referred to as suffering from the Celtic curse because there are high levels of these neural tube defects present within them. Ethnic differences can also be found in California where the Hispanic population has a higher incidence than the African American population overall.

    01:13 Similarly, even within families, if one sibling has been affected by a neural tube defect, then other members of the family have a higher chance of being affected, likewise.

    01:25 We do know that there’s not a single gene that’s responsible for this. In fact, there may be hundreds of genes which are involved in various ways, and at various times during the course of development. There’s also an interaction with genes and the environment so some environmental factors can increase the incidence. One common example is sodium valproate, a drug taken to reduce the instance of epileptic attacks. Since this is a drug that people may well be taking over an extended period of time, it poses a hazard if it was a female who’s taking the drug and who is planning to become pregnant during that time period.

    02:03 However, there are ways of reducing the frequency of neural tube defects of this kind, even in populations where there’s a strong predisposition towards it. One of the most effective ways is folic acid, which is a B vitamin. Therefore, we cannot synthesize it and we have to eat it in our food. It’s present in some foods, but frankly, it’s hard to eat enough broccoli in order to get the levels of folic acid that you need. Strawberries might be more straightforward.

    02:30 So the guidance is that if women are planning pregnancy, then they can be given a supplement, 400 micrograms of folic acid per day before fertilization takes place. It will prevent nearly 70 percent of neural tube defects from occurring. This can be taken in the form of tablets. Since many women do not know that they were planning to become pregnant, pregnancy comes as a surprise to them; another alternative strategy would be to supplement basic food stuffs.

    03:01 Flour would be a good example, so that the whole population is exposed to higher levels of this particular vitamin, folic acid, in order to prevent this as a possibility.

    03:11 And both strategies, both taking tablets and supplementing food stuffs are successful in reducing the incidence of neural tube defects. So then, if we summarize what we looked at in this lecture, we looked first of all at the basics of formation of the neural tube from very early stages. We looked at the early stages of brain development, and we’ll return to that in a later lecture. And we also looked at neural tube defects. Thank you very much.

    About the Lecture

    The lecture Neural Tube Defects – Neurulation by John McLachlan, PhD is from the course Embryology: Early Stages with John McLachlan.

    Author of lecture Neural Tube Defects – Neurulation

     John McLachlan, PhD

    John McLachlan, PhD

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