Neural tube defect

neural tube defectsspinal dysraphismdefectsfetal brain formationFetal valproate syndromefolate fortificationNeural tube defects X linkedneural tube disorders'''pinal dysraphism
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development.wikipedia
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Birth defect

congenitalcongenital disorderbirth defects
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development.
The types with the greatest numbers of deaths are congenital heart disease (303,000), followed by neural tube defects (65,000).

Anencephaly

anencephalicAnencephalusanencephalic infant
Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems. Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida.
It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fails to close, usually between the 23rd and 26th day following conception.

Encephalocele

Meningoencephalocele sac-like protrusions of the brain and the membranes that cover it through openings in the skullmeningoencephaloceles
Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems. Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida.
Encephalocele, is a neural tube defect characterized by sac-like protrusions of the brain and the membranes that cover it through openings in the skull.

Neural tube

neural canalneural canalsdorsal neural tube
In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube.
Improper closure of the neuropores can result in neural tube defects such as anencephaly or spina bifida.

Spina bifida

myelomeningocelemeningocelespina bifida occulta
Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems. Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida.
Spina bifida is a type of neural tube defect related to but distinct from other types such as anencephaly and encephalocele.

Methylenetetrahydrofolate reductase

MTHFR5-MTHF reductaseEC 1.5.1.20
The association seen between reduced neural tube defects and folic acid supplementation is due to a gene-environment interaction such as vulnerability caused by the C677T Methylenetetrahydrofolate reductase (MTHFR) variant.
Although some variants have been reported to influence susceptibility to occlusive vascular disease, neural tube defects, Alzheimer's disease and other forms of dementia, colon cancer, and acute leukemia, findings from small early studies have not been reproduced.

Folate

folic acidfolate biosynthesisone carbon pool by folate
Inadequate levels of folate (vitamin B9) and vitamin B12 during pregnancy have been found to lead to increased risk of NTDs.
Folic acid is also used as a supplement by women during pregnancy to reduce the risk of neural tube defects (NTDs) in the baby.

Homocysteine

homocysteinemiaL-Homocysteine
A mechanism by which maternal exposure to cigarette smoke could increase NTD risk in offspring is suggested by several studies that show an association between cigarette smoking and elevations of homocysteine levels.
Hyperhomocysteinemia has also been associated with early pregnancy loss and with neural tube defects.

Triploid syndrome

triploidy
There are also several syndromes such as Meckel syndrome, and Triploid Syndrome which are frequently accompanied by neural tube defects that are assumed to be unrelated to folate metabolism
Common central nervous system defects seen in triploidy include holoprosencephaly, hydrocephalus (increased amount of cerebrospinal fluid within the brain), ventriculomegaly, Arnold–Chiari malformation, agenesis of the corpus callosum and neural tube defects.

Triple test

Quad screenQuad testQuad blood test
Tests for neural tube defects include ultrasound examination and measurement of maternal serum alpha-fetoprotein (MSAFP).
In addition to Down syndrome, the triple and quadruple screens assess risk for fetal trisomy 18 also known as Edward's syndrome, open neural tube defects, and may also detect an increased risk of Turner syndrome, triploidy, trisomy 16 mosaicism, fetal death, Smith–Lemli–Opitz syndrome, and steroid sulfatase deficiency.

Alpha-fetoprotein

AFPalpha fetoproteinα-fetoprotein
Tests for neural tube defects include ultrasound examination and measurement of maternal serum alpha-fetoprotein (MSAFP).

Meckel syndrome

Meckel-Gruber syndromeMeckel–Gruber syndromeDysencephalia splachnocystica or Meckel–Gruber
There are also several syndromes such as Meckel syndrome, and Triploid Syndrome which are frequently accompanied by neural tube defects that are assumed to be unrelated to folate metabolism
It is estimated that Meckel syndrome accounts for 5% of all neural tube defects there.

Gastrulation

gastrulablastoporedorsal lip
In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube.

Vertebral column

spinespinal columnspinal
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems.

Brain

brain functionmammalian braincerebral
Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems.

Skull

craniumcranialhuman skull
Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems.

Iniencephaly

Specific types include: spina bifida which affects the spine, anencephaly which results in little to no brain, encephalocele which affects the skull, and iniencephaly which results in severe neck problems. Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida.

Hydranencephaly

hydrancephaly
Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida. Hydranencephaly is a condition in which the cerebral hemispheres are missing and instead filled with sacs of cerebrospinal fluid.

Schizencephaly

Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida.

Tethered spinal cord syndrome

tethered cordtethered spinal cordcord tethering
Common examples of closed NTDs are lipomyelomeningocele, lipomeningocele, and tethered cord.

Cerebral hemisphere

hemispherecerebral hemisphereshemispheres
Hydranencephaly is a condition in which the cerebral hemispheres are missing and instead filled with sacs of cerebrospinal fluid.

Vertebra

vertebraeneural spineneural arch
The most frequently seen form of spina bifida occulta is when parts of the bones of the spine, called the spinous process, and the neural arch appear abnormal on a radiogram, without involvement of the spinal cord and spinal nerves.

Vitamin B12

vitamin B 12 cobalaminB12
Inadequate levels of folate (vitamin B9) and vitamin B12 during pregnancy have been found to lead to increased risk of NTDs.

Gene–environment interaction

gene-environment interactiongene-environment interactionsinteraction
The association seen between reduced neural tube defects and folic acid supplementation is due to a gene-environment interaction such as vulnerability caused by the C677T Methylenetetrahydrofolate reductase (MTHFR) variant.

Methotrexate

amethopterin(M)'''ethotrexateAbitrexate
Other potential causes can include folate antimetabolites (such as methotrexate), mycotoxins in contaminated corn meal, arsenic, hyperthermia in early development, and radiation.