What is the Difference Between Acrania and Anencephaly?
🆚 Go to Comparative Table 🆚Acrania and anencephaly are both congenital disorders that affect the development of the brain and skull, but they differ in the presence of brain tissue.
Acrania:
- Acrania is the absence of the fetal skull, resulting in brain tissue being exposed to the amniotic fluid.
- It is thought to be the precursor to anencephaly, as part of a progression called the acrania-exencephaly-anencephaly sequence.
- The brain tissue is present in acrania.
- Acrania can be diagnosed on ultrasound in the first trimester.
Anencephaly:
- Anencephaly refers to the absence of the upper portion of the fetal brain.
- It is thought to result from acrania, as the amniotic fluid is toxic to and eventually destroys the exposed fetal brain tissue.
- The remaining parts of the brain remain exposed, not covered by bone or skin.
- The brain tissue is absent in anencephaly.
Both acrania and anencephaly are part of a group of birth defects called neural tube defects (NTDs), which occur when the neural tube, a structure that forms the early brain and spine, fails to close within the first month of pregnancy. These conditions are typically fatal, with infants born with anencephaly not surviving for very long after birth.
Comparative Table: Acrania vs Anencephaly
Acrania and anencephaly are both congenital disorders that affect the development of the brain and skull in infants. The main difference between the two conditions lies in the presence or absence of brain tissue. Here is a table summarizing the differences between acrania and anencephaly:
| Feature | Acrania | Anencephaly |
|---|---|---|
| Brain Tissue | Present | Absent |
| Skull Development | Absence of the neurocranium (calvarial bones, dura mater, and associated muscles) | Absence of the upper portion of the fetal brain |
| Symptoms | Exposure of the brain tissue with the absence of the skull, impaired consciousness, high mortality rate | Absence of the cerebral hemispheres and the cerebellum, exposure of the brain tissue with the absence of the skull, impaired consciousness, high mortality rate |
| Diagnosis | Can be seen on ultrasound in the first trimester | Prenatal diagnosis is straightforward, but careful examination is required to avoid confusion with acrania, acephaly, or amniotic band syndrome |
| Prevalence | Thought to be the precursor to anencephaly in a sequence called the acrania-exencephaly sequence | The incidence of anencephaly is about 1 in 1,000 births, but has decreased dramatically in recent years |
Both acrania and anencephaly are lethal disorders, meaning that babies born with these conditions cannot survive for very long.
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