The key difference between exencephaly and anencephaly is that exencephaly is a cephalic disorder in which the brain tissues are located outside the skull due to the absence of cranial cavity and scalp. Meanwhile, anencephaly is a cephalic disorder which is characterized by the absence of a major portion of the brain, skull and scalp due to the failure of the rostral neuropore to close.
Congenital disorders arise due to neural defects that take place during pregnancy. They give rise to a high degree of mortality, making the condition fatal. Exencephaly and anencephaly are two such congenital disorders as well as cephalic disorders seen in infants. In exencephaly, the brain is located outside the skull. In anencephaly, a major portion of the brain, skull and scalp are absent. Exencephaly is considered to be an embryological precursor of anencephaly. However, exencephaly is extremely a rare condition compared to anencephaly.
CONTENTS
1. Overview and Key Difference
2. What is Exencephaly
3. What is Anencephaly
4. Similarities Between Exencephaly and Anencephaly
5. Side by Side Comparison – Exencephaly vs Anencephaly in Tabular Form
6. Summary
What is Exencephaly?
Exencephaly is a condition seen in the early embryo. It is a type of cephalic disorder in which the brain is located outside the skull. It occurs due to the absence of the cranial cavity and scalp. Therefore, a large amount of brain tissue is found protruding outside. Moreover, this disorder is characterized by prominent bulging eyeballs. When exencephaly takes place, it causes the gradual degeneration of brain tissues due to the exposure to amniotic fluid in combination with mechanical trauma.
Figure 01: Exencephaly
Exencephaly is a very rare disorder. It is very difficult to find an infant bone with exencephaly since most exencephalics are stillborn.
What is Anencephaly?
Anencephaly refers to the incomplete development of the brain, skull and the scalp. A neural tube defect takes place during embryonic development. They occur during the third and fourth weeks of pregnancy. During anencephaly, the neural tube does not close properly. This results in the incomplete development of the brain or failure of brain development. Anencephaly is the most common neural tube disorder seen in infants.
Figure 02: Anencephaly
Anencephaly is a genetic disorder. In fact, it is a multifactorial condition where multiple genes and environmental factors are involved in the onset. It may also occur due to a chromosomal aberration (trisomy 18). There are several characteristics associated with anencephaly. They are the absence of the front part of the brain (forebrain), absence of the cerebral hemispheres and the cerebellum, exposure of the brain tissue with the absence of the skull, impaired consciousness and high mortality rate.
What are the Similarities Between Exencephaly and Anencephaly?
- Exencephaly and anencephaly are cephalic disorders arising due to neural tube defects.
- Both disorders are related to the central nervous system and head.
- In fact, both types of disorders arise due to malformation of the neural tube.
- These diseases occur during embryonic development.
- Moreover, both these disorders are lethal and cannot be treated.
What is the Difference Between Exencephaly and Anencephaly?
Exencephaly is a cephalic disorder in which a large amount of brain tissues protrudes out of the cranial cavity and is not covered by the skin while anencephaly is the complete absence of major parts of the brain, skull and scalp due to the failure of rostral neuropore to close. So, this is the key difference between exencephaly and anencephaly. Exencephaly is less common in infants while anencephaly is the most common neural tube disorder seen in infants.
Below infographic summarizes the difference between exencephaly and anencephaly.
Summary – Exencephaly vs Anencephaly
Anencephaly and exencephaly are two congenital central nervous system abnormalities. Exencephaly is the cephalic disorder which is characterized by the presence of brain tissues outside the skull. Anencephaly is the cephalic disorder which is characterized by the absence of major portions of the brain, skull and scalp. It occurs due to the failure of rostral neuropore to close at birth. Exencephaly is a very rare condition and most cases are stillborn. Whereas, anencephaly is the most common neural tube defect seen in infants. Most importantly, both of these cephalic disorders are uniformly lethal and cannot be treated. So, this summarizes the difference between exencephaly and anencephaly.
Reference:
1. Renuka, I V, et al. “Exencephaly in a Live, Full Term Fetus.” Journal of Pediatric Neurosciences, Medknow Publications, July 2009, Available here.
2. “Exencephaly.” Exencephaly – an Overview | ScienceDirect Topics, Available here.
Image Courtesy:
1. “Image from page 69 of “The American journal of anatomy” (1917)” By Internet Archive Book Images (No known copyright restrictions) via Flickr
2. “Anencephalic baby” By Centers for Disease Control and Prevention – (Public Domain) via Commons Wikimedia