Sign Up for a Free Account

This is an image preview.
Start a Free Account
to view the full image.

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.


Anencephaly is a fatal neural tube defect in which the cerebral hemispheres do not develop, although some highly disorganized brainstem tissue is typically present. Prenatal screening for neural tube defects has significantly decreased the number of births of infants with anencephaly, and prevention of maternal folate deficiency (now known to be an etiologic factor) is expected to reduce the incidence even further. All women of childbearing age should take folate supplements to reduce the risk of this anomaly. (Photograph by Ed Uthman MD, January 13, 2002. Public domain.)