Neural tube defects

Submitted by Rabia Mustafa king Edward medical university

Neural tube defects:The brain and spinal cord are derived from ectodermal elements that differentiate and proliferate to form the neural tube. Closure to the neural tube begins on approximately the 22nd day of gestation and is complete between the 26th and 28th day. Disorders related to abnormal closure of the neural tube defects or dystrophic states may involve the brain or spinal cord or both .example include,

Anencephaly Cranial meningeoceles Encepaloceles Various forms of spina bifida

1. Anencephaly:Anencephaly with or without associated spinal abnormalities represent the most severe form of neural tube defect and is most severe form of neural tube defect and is most common CNS malformation identified in human fetus . anencephaly occur in about 1 in 500 births and is encountered worldwide albeit with substantial regional variations in frequency as with all neural tube defects it is more common among lower socioeconomic groups and infants of women older than age 40 years . Epidemiological studies have shown a reasonably convincing association between dietary folate deficiencies and an increased risk of anencephaly. For reasons that remain unclear female fetus are more commonly affected .

Causes and Risk Factors:

Like many families affected by birth defects, CDC wants to find out what causes them. Research gives us important clues about things that might raise or lower the risk of having a baby affected by birth defects, such as anencephaly. Those clues help us develop sound public health policies for prevention.

CDC works with many other researchers to study risk factors that can increase the chance of having a baby affected by anencephaly. Scientists believe that many factors such as genes, behaviors, and things in the environment are involved. CDC researchers have reported important findings about some factors that affect the risk for anencephaly:

Low intake of folic acid before getting pregnant and in early pregnancy increases the risk of having a pregnancy affected by neural tube defects, including anencephaly

There has been a 27% decline in pregnancies affected by nueral tube defects (spina bifida and anencephaly) since the United States began fortifying grains with folic acid

Babies born to Hispanic mothers are at an increased risk for anencephaly.3

Reasons for the increased risk among Hispanic mothers are not well understood.

CDC continues to study birth defects like anencephaly and how to prevent them. If you are pregnant or thinking about becoming pregnant, talk with your doctor about ways to increase your chance of having a healthy baby.

Diagnosis:

Anencephaly can be diagnosed during pregnancy or after the baby is born.

During Pregnancy:

During pregnancy, there are screening tests (prenatal tests) to check for birth defects and other conditions. Anencephaly would result in an abnormal result on a blood or serum screening test or it might be seen during an ultrasound (which creates pictures of the body).

After the Baby is Born:

In some cases, anencephaly might not be diagnosed until after the baby is born. Anencephaly is immediately seen at birth.

Treatments:

There is no known cure or standard treatment for anencephaly. Almost all babies born with anencephaly will die shortly after birth.

Craniorachischisis: Craniorachischisis is a developmental defect that

occurs during the fetal gestation period. It is characterized by malformation of the skull and spinal bone which results in exposure of the brain .

Symptoms of Craniorachischisis:

Absent portion of skull Exposed brain

Spine defect Imperforate anus Diaphragmic hernia

Craniorachischisis Causes

The cause of Craniorachischisis is due to failure of the neural tube to close during the

early stages of fetal development; about the third to fourth week of the gestation period.

NTDs are believed to result from a combination of genetic and environmental factors.

In some cases, chromosomal abnormalities have been observed. It is thought that

exposure to valporic

Craniorachischisis Diagnosis & Tests

Early detection of Craniorachischisis is possible through fetal ultrasound and Alpha-

fetoprotein screening. Both of these are routinely done in prenatal care. Acid, arsenic,

mycotoxins, folate ant metabolites, or other toxins during the six weeks after a previous

menstrual cycle may cause problems with the metabolism of folate and increase the risk

of developmental problems occurring.

There is no cure or treatment for Craniorachischisis. Though rare, this defect is so

severe that fetal death is almost certain. In the rare instances in which a fetus with

Craniorachischisis remained viable to birth, infant death occurred shortly thereafter.

.

3. Iniencephaly

Iniencephaly is failure of normal neural tube closure between the 3rd and 4th week of

embryologic development. Iniencephaly is a term derived from the Greek word “inion”

for nape of the neck, is a rare type of cephalic disorder that was first described by

Etienne Geoffrey in 1836. Those afflicted with the disorder all share 3 common

characteristic defect to the occipital bone , spinal bifida of the cervical vertebrae and

retro flexion (backward bending) of the head on the cervical spine . Stillbirth is the most

common outcome, with a few rare examples of live birth, after which death almost

invariably occurs within a short time Iniencephaly is a rare condition during prenatal

life. When diagnosed early in pregnancy multidisciplinary approach is firmly suggested.

Iniencephaly is a rare congenital malformation resulting from a defective neuro

developmental process occurring in early pregnancy. The developmental pathogenesis is

not known. It has been suggested that Iniencephaly is probably an extreme form of

Klippel-Feil syndrome or may belong to a spectrum of central nervous system (CNS)

anomalies that includes anencephaly and spina bifida. The recurrence risk is less than

1% and this rate may be higher in families with a history of neural tube defects. In

Turkey the incidence of neural tube defect was found to be 3 in 10 000 Failure of

normal neural tube closure between the 3rd and 4th week of embryologic development

Signs and symptoms of Iniencephaly:

The affected infant tends to be short, with a disproportionately large head. The fetal

head of Infants born with Iniencephaly are hyper extended while the foramen

magnum is enlarged and opens through the widened pedicles. The defective neural

arches directly into the upper cervical reach of the spinal canal, causing the

formation of a common cavity between most of the spinal cord and the brain. The

skin of the anterior chest is connected directly to the face, bypassing the formation

of a neck, while the scalp is directly connected to the skin of the back.

Epidemiology :

2nd most common fetal malformation

1~2/1000

Geographic variation

Multifactorial in origin

Nutritional deficiency

Anticonvulsant agents

Zinc deficiency, hyperthermia, aminopterin, clomiphene citrate, IDDM

Genetic factor

4. Encepaloceles: Encepaloceles is one of a group of birth defects known as neural tube defects (NTD).

It occurs very early in fatal life where the neural tube does not close properly

resulting in brain tissue protruding from the skull into a sac3.

Encepaloceles occurs in about 1 to 2 of every 10,000 births in the United States5. Of those babies, only 20% of them are born alive, and only half of those survive. For an unknown reason, 70% of occipital (back of the skull) Encepaloceles occur in females,

whereas anterior (front of the skull) encephaloceles are more often seen in males3. Up to 40% of Encepaloceles cases occur in babies who have chromosomal

abnormalities5. The brains of children with Encepaloceles do not form normally, which may result in developmental delay, learning problems, or mental retardation.

Causes and risk factors :

The causes for Encepaloceles are unknown. However, it has been shown that genetic and environmental risk factors play an important role. Mothers with the following characteristics have been found to be at higher risk for having a baby with Encepaloceles:

• Maternal lack of folic acid and vitamins

• Previous baby with NTD (1 in 25)

• Family history of NTD

• Diabetes Maternal obesity

• during pregnancy

• Maternal stress

• Woman who has epileptic seizures

Prevention:

Folic acid is a B vitamin that plays an important role in the development of the fatal brain and spinal cord during very early pregnancy, often before many women know they are pregnant. For this reason and because many pregnancies are unplanned, it is recommended that all women of childbearing age take 400 (0.4mg) micrograms of folic acid per day through dietary supplements of foods that are fortified with folate. It has been shown that taking the recommended dose can reduce the risk of neural tube defects by up to 70%. Encepaloceles may be detected during the middle of the second trimester of pregnancy using high-level ultrasound examination. It may not be detected by prenatal blood testing because alpha protein levels are not typically elevated when the defect is covered by skin. If an Encepaloceles is detected, a specialist that handles high-risk pregnancies should be consulted. Women who think that they may be in a high risk category should have genetic counselling.

Medical care : Treatment may include immediate surgery to remove the sac and replace the brain tissue into the skull. A computerized tomogram (CT) scan or other studies may be done to determine the extent of the lesion. Long-term treatment depends on the extent of the defect. The fetus should be delivered at a facility that has personnel capable of handling all aspects of neonatal complications.

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