Anencephaly is the absence of a large part of the brain and the skull. It is one of the most common neural tube defects. Neural tube defects are birth defects that affect the tissue that grows into the spinal cord and brain. Possible causes include environmental toxins and low intake of folic acid by the mother during pregnancy.
Symptoms include the absence of the skull, absence of the brain (cerebral hemispheres and cerebellum), facial feature abnormalities, and heart defects. A pregnancy ultrasound is done to confirm the diagnosis.
(Source: Flickr / jgmundie)