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REVISED Neural Tube 18 10 2018

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Neural Tube Defects
Dr. Nasreen Feroze/ Roll No. 701/2018 P a g e | 2 [Type here]
INTRODUCTION
Neural tube defects are congenital abnormalities of CNs that develop because of mal
union of neural folds completely. It has an incidence of 300000/year over worldwide.
No exact data is not available but in Pakistan it has a prevalence rate of 4.5/1000 total
births.
There are 2 types of defects.
Open
Closed
Open neural tube defects are most common. Open NTD occur when brain or spinal
cord is exposed at birth through a hole in the skull or vertebrae.
In open category included are anencephaly, encephalocele, hydrocephaly,
schizocephaly, spina bifida Rare varieties are closed defects which occur when spinal
defect is covered by skin. These include,meningocele, myeilomeningocle and tethered
cord.
There are multiple causative agents of these defects. There are genetics reasons plus
environmental. There are deficient studies on genetics but multiple nutritional factors
came out on front lines as their supply to pregnant ladies prevented the defects.
Numerous Genetic functioning abnormality, regularity of membrane morphology is
essential for normal closing.
Multifactorial Threshold Model is applied in development of NTD since single genetic

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Neural Tube Defects
Dr. Nasreen Feroze/ Roll No. 701/2018 P a g e | 3 [Type here]
aberration is insufficient to cause defect. There is interaction of genes to genes and
genes to environment to cause the defect.
EMBRYOLOGY
Formation of Neutral tubes involves the bending of neuroepithelium at midline to
generate neural folds. These neural folds elevate and fuse in the midline in a process
called (Primary Neurulation). If incomplete closure neural tube is exposed to
environment and undergoes degeneration so that neuronal deficit develops. The
severity of defects depends on which axis is deficient. If fusion of brain affected, then
defect like anencepaly develops and if spinal cord affected then spinal bifida like
abnormalities come out. NTD can be due to either failure of initiating events or
disturbance of closing events at these sites. This process of primary Neuralation take
place at 18 days after fertilization when mostly women do not know that they are
pregnant + process complete till 28 days after fertilization.
Secondary Neurulation
This is the process by which neural tube below to the mid sacral region is continuous
with the lower end primary neural tube forms. There is a population of tail bud cells
that condense here to form an epithelial rod which canalizes
to form tube lumen in lower sacral and coccygeal region. There is skin covered
malformation which makes ectopic lipomaous materials by spinal cord tethering.

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Neural Tube Defects INTRODUCTION Neural tube defects are congenital abnormalities of CNs that develop because of mal union of neural folds completely. It has an incidence of 300000/year over worldwide. No exact data is not available but in Pakistan it has a prevalence rate of 4.5/1000 total births. There are 2 types of defects. Open Closed Open neural tube defects are most common. Open NTD occur when brain or spinal cord is exposed at birth through a hole in the skull or vertebrae. In open category included are anencephaly, encephalocele, hydrocephaly, schizocephaly, spina bifida Rare varieties are closed defects which occur when spinal defect is covered by skin. These include,meningocele, myeilomeningocle and tethered cord. There are multiple causative agents of these defects. There are genetics reasons plus environmental. There are deficient studies on genetics but multiple nutritional factors came out on front lines as their supply to pregnant ladies prevented the defects. Numerous Genetic functioning abnormality, regularity of membrane morphology is essential for normal closing. Multifactorial Threshold Model is applied in development of NTD since single genetic Dr. Nasreen Feroze/ Roll No. 701/2018 Page |2 [Type here] Neural Tube Defects aberration is insufficient to cause defect. There is interaction of genes to genes and genes to environment to cause the defect. EMBRYOLOGY Formation of Neutral tubes involves the bending of neuroepithelium at midline to generate ...
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