Anencephaly is due to failure of the anterior neural tube to close properly during very early intrauterine life.
Mothers with infants having neural tube defects have high levels of alpha feto-protein.
Anencephaly has been related to low levels of folic acid, obesity, hypervitaminosis A and previous infants with neural tube defects.
The lesion is sporadic and has no chromosomal abnormality as far as is known.,
Anencephaly is seen in the United States at a frequency of 1:1000 births.
However, if a woman has an infant with a neural tube defect, her chance of a second infant having the defect is 1:50, if she has 2 infants with the defect her chance of a third is 1:25 etc.
|General Gross Description|
In anencephaly, the infant is born with no cerebral hemispheres, only a rudimentary brainstem and brainstem, and no calvarium (skull bone).
Often there are associated malformations such as cleft lip and palate, abnormalities of hands and feet and other internal malformations.
Usually associated with bulging, frog-like, eyes.
|General Microscopic Description|
Microscopically the brain consists of a cerebrovasculosum, a hemorrhagic portion of tissue made up of disorganized glial and neuronal tissue, leptomeninges, and many blood vessels.
The brainstem is abnormal with no pyramids or corticospinal tracts and other variable abnormalities and there may be a vestige of a cerebellum.
Anencephaly is usually sporadic with a frequency of 1:1000 births in the United States, but 5:1000 in Ireland and lesser numbers in Asia.
Infants affected usually die at birth or in a matter of weeks.
Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1301.
Poirer J et.al. Manual of basic neuropathology. Philadelphia: Saunders, 1990, pp.197.
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||Synopsis by: M.L. Grunnet M.D. (TX2000M21000)