The third way in which the Mickey Mouse sign can show up in medicine is via ultrasound scanning in the detection of anencephaly. Anencephaly is the absence of a large part of the brain and the skull. It is the most common abnormality affecting the central nervous system (brain and spine). Most babies born with this condition do not survive birth. The picture below (copyrighted by Wiley from this article) shows the appearance of a Mickey Mouse face on the ultrasound. In reality, it is showing a large amount of protruding, abnormally developed brain tissue. The sign was first identified in 1994 and its presence helps diagnose anencephaly early in pregnancy. Be sure to check out the first Mickey Mouse sign, the second Mickey Mouse sign, and the fourth Mickey Mouse sign.