Anencephaly
Anencephaly is a defect in the fusion of several closure sites of the neural tube (2 for the merocranium and 2 and 4 for the holocranium) in the neurulation process during embryogenesis. It occurs when the brain end or head of the neural tube fails to close, usually between the age of 23.er and the 26th day of pregnancy, resulting in a congenital brain malformation characterized by the partial or total absence of the brain, skull and scalp.
Description
Although the cerebral hemispheres can develop under this condition, any exposed brain tissue is subsequently destroyed. This produces a fibrotic and hemorrhagic mass of neurons and glial cells as well as a non-functional cerebral cortex. Additionally the brainstem and cerebellum are spared. Because of these severe abnormalities, the skull base and facial bones do not show average or near average development. The frontal bone is almost always absent and the brain tissue is abnormal.
Anencephaly is divided into two subcategories: the milder known as meroacrania, which describes a small defect in the cranial chamber covered by the cerebrovascular area, and the more severe known as holoacrania where the brain is completely absent.
In children born with anencephaly, the braincase has not closed, the cranial vault does not exist, and different structures and relevant parts of the cranial bones, meninges, scalp, and scalp are missing to a greater or lesser extent. cerebral cortex and brain. Under these conditions, newborns are unconscious, as well as blind, deaf, and insensitive to pain. The activity is usually reduced to respiratory and the presence of some elementary reflexes. The brainstem is developed only in 25% of cases and in a very rudimentary way. They also present a poor development of the pituitary gland. Life expectancy at birth is only a few days or hours after birth. In rare cases, some individuals can survive for several years.
Epidemiology
This condition is one of the less common disorders of the fetal central nervous system. Its frequency varies between 1 and 2 per 1000 births. The disorder affects women more often than men in a ratio of 3-4:1. Something similar is observed between ethnic groups where there is a higher prevalence in Caucasian populations compared to other populations.
Etiology
The causes of anencephaly are unknown. Although it is believed that the mother's diet and vitamin intake may play a role, scientists say there are many other factors involved. Recent investigations include among the possible causes ingestion of antiepilepsy drugs during pregnancy, mechanical aggression, contact with pesticides, environmental factors, radiation, deficiency in transcription factors involved in the closure of the neural tube associated with low levels of folic acid (Vitamin B9 water soluble) and chromosomal abnormalities of the aneuploidy or trisomy type.
Anencephaly has been quite controversial since it is believed that its pathology may be caused by routes other than neural tube closure. There is an alternative hypothesis where the disease is due to a primary mesenchymal abnormality where the brain is lost secondarily due to damage caused by its exposed position within the uterus. [citation required]
Treatment
There is no cure or standard treatment for anencephaly, and the prognosis for affected individuals is poor. Most patients do not survive childhood. If the child is not stillborn, it usually dies a few hours or days after birth. Anencephaly can often be diagnosed during pregnancy by measuring the level of alpha feto protein or AFP (which is abruptly elevated) in the amniotic fluid by amniocentesis or through an ultrasound test between the 10th and 14th. th week of pregnancy