Acrania

Acrania: Definition, Description, Causes and Risk Factors: Acrania is a rare congenital disorder that occurs in the human fetus in which the flat bones in the cranial vault are either completely or partially absent. The cerebral hemispheres develop completely but abnormally. The condition is frequently, though not always, associated with anencephaly. The fetus is said to suffer from acrania if it meets the following criteria: the fetus should have a perfectly normal facial bone, a normal cervical column but without the fetal skull and a volume of brain tissue equivalent to at least one third of the normal brain size. Acrania There are no known family ties in acrania and reoccurrence rates are extremely low. Not much is known about the exact mechanism involved in acrania. It is hypothesized that like other developmental malformations, there are multiple origins for acrania. Recent work has identified mutations in the HHAT gene that have caused Acrania along with holoprosencephaly and agnathia. The mutation in HHAT which causes this disease is a loss-of-function mutation. Before this discovery in 2010, HHAT was known to play a role in the Sonic Hedgehog Pathway. When HHAT is mutated less is produces. HHAT is necessary for the production of Hedgehog (Hh) proteins post-transcriptionally. As HHAT production decreases, production of long-range Hh proteins decreases proportionally. Decreases in Hh production disturb the production of Erk, Bmp, and Fgf, all of which play important roles in craniofacial patterning. Disruption of these pathways leads to abnormal bone and cartilage formation causing Acrania and multiple other craniofacial patterning problems. There is a 100% mortality rate for those with Acrania. This disease is rare, occurring in 1 in 20,000 live births. In order to better manage an Acrania diagnosis, early detection is of extreme importance so that actions may be taken to help the mother and child. Families may choose to either terminate the pregnancy, or carry the child to term. Acrania may cause a fetus to spontaneously abort before reaching term.  

Acrania Symptoms:

A variety of other abnormalities can be seen with acrania. Many fetuses with this condition also have anencephaly, where part of the brain is missing along with the skull and scalp. Cleft lip, heart defects, and gastrointestinal abnormalities can also occur. Acrania on its own is invariably fatal, and these other defects may not be diagnosed unless parents specifically request an autopsy. Diagnosis: Acrania can be diagnosed early in pregnancy through an ultrasound. This anomaly appears during the beginning or end of the fourth week of the fetus's development. An absence of the skull is needed in order to make a diagnosis. A presence of brain tissue will confirm the diagnosis of Acrania and differentiate it from other developmental problems such as Anencephaly.

Treatment:

Sadly, there is no medical treatment for Acrania. Due to the lack of development of babies' brains, about 75 percent of infants are stillborn and the remaining 25 percent of babies die within a few hours, days or weeks after delivery. Care focuses on providing emotional support to your family. Our social workers will offer you a network of support groups with families going through similar issues. Many families find consolation knowing their child has not been forgotten by those who cared for him or her and that there are others who share in their grief. Also, we may recommend genetic counseling for parents to discuss the risk of recurrence in a future pregnancy as well as vitamin therapy (a prescription for folic acid) that can decrease the recurrence for ONTDs. Extra folic acid, a B vitamin, if taken one to two months prior to conception and throughout the first trimester of pregnancy, has been found to decrease the reoccurrence of ONTDs, for couples who have had a previous child with an ONTD. NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

2 Comments

  1. Kristi

    What does the O stand for in ONTD? I know what neural tube defects are, but am not familiar with ONTDs.

    Reply
    • editor-m

      Open neural tube defects. Open NTDs frequently involve the entire CNS (eg, associated hydrocephalus, Chiari II malformation) and are due to failure of primary neurulation. Closed NTDs are localized and confined to the spine (brain rarely affected) and result from a defect in secondary neurulation.

      Reply

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