Official reprint from UpToDate®
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Tadanori Tomita, MD
Hideki Ogiwara, MD, PhD
Section Editors
Marc C Patterson, MD, FRACP
Leonard E Weisman, MD
Deputy Editor
Carrie Armsby, MD, MPH


Anencephaly is characterized by an open defect in the calvaria and skin, such that the cranial neural tube is exposed. It is a severe defect and is not compatible with survival. Infants that are alive at birth generally die within hours but occasionally survive for a few days or weeks. The clinical features, diagnosis, and management of anencephaly are discussed in this topic review.

Anencephaly is one of the three major neural tube defects (NTDs). The others are encephalocele and myelomeningocele, which are discussed in separate topic reviews:

Encephalocele, which is a herniation of the brain and/or meninges through a defect in the skull (cranium bifidum) that is “closed” or covered with skin. (See "Primary (congenital) encephalocele".)  

Myelomeningocele, which is characterized by a cleft in the vertebral column, with a corresponding defect in the skin so that the meninges and spinal cord are exposed. (See "Pathophysiology and clinical manifestations of myelomeningocele (spina bifida)" and "Overview of the management of myelomeningocele (spina bifida)".)


The central nervous system (CNS) appears as a plate of thickened ectoderm called the neural plate at the beginning of the third week of embryonic life. The lateral edges of the neural plate become elevated to form the neural folds and fuse to form the neural tube; the fusion begins in the cervical region and proceeds in both the rostral and caudal directions (figure 1). The rostral neuropore closes on the 25th day after conception, and the caudal neuropore closes two days later [1]. Neural tube defects (NTDs) result from failure of the neural tube closure between 25 and 27 days after conception. The embryology of the neural tube is discussed in a separate topic review. (See "Closed spinal dysraphism: Pathogenesis and types", section on 'Normal cord development in humans'.)


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Literature review current through: Sep 2016. | This topic last updated: Jun 25, 2015.
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  1. Sadler TW. Langman's Medical Embryology, Lippincott Williams & Wilkins, Philadelphia 1990. p.352.
  2. Lemire RJ, Beckwith JB, Warkuny J. Anencephaly, Raven Press, New York 1978.
  3. Stone DH. The declining prevalence of anencephalus and spina bifida: its nature, causes and implications. Dev Med Child Neurol 1987; 29:541.
  4. O'Rahilly M, Muller F. Human Embryology & Teratology, Wiley-Liss, Inc, New York 1992. p.253.
  5. Sarnat HB, Flores-Sarnat L. Embryology of the neural crest: its inductive role in the neurocutaneous syndromes. J Child Neurol 2005; 20:637.
  6. Coskun A, Kiran G, Ozdemir O. Craniorachischisis totalis: a case report and review of the literature. Fetal Diagn Ther 2009; 25:21.
  7. Naveen N, Vishal K, Maligi A. Craniorachischisis totalis. J Neurosci Rural Pract 2010; 1:54.
  8. Mathews TJ, Honein MA, Erickson JD. Spina bifida and anencephaly prevalence--United States, 1991-2001. MMWR Recomm Rep 2002; 51:9.
  9. Boulet SL, Yang Q, Mai C, et al. Trends in the postfortification prevalence of spina bifida and anencephaly in the United States. Birth Defects Res A Clin Mol Teratol 2008; 82:527.
  10. Volpe JJ. Intracranial hemorrhage: Neural tube formation and prosencephalic development. In: Neurology of the Newborn, 4th, WB Saunders, Philadelphia 2001. p.3.
  11. Frey L, Hauser WA. Epidemiology of neural tube defects. Epilepsia 2003; 44 Suppl 3:4.
  12. Li Z, Ren A, Zhang L, et al. Extremely high prevalence of neural tube defects in a 4-county area in Shanxi Province, China. Birth Defects Res A Clin Mol Teratol 2006; 76:237.
  13. Cowchock S, Ainbender E, Prescott G, et al. The recurrence risk for neural tube defects in the United States: a collaborative study. Am J Med Genet 1980; 5:309.
  14. Toriello HV, Higgins JV. Occurrence of neural tube defects among first-, second-, and third-degree relatives of probands: results of a United States study. Am J Med Genet 1983; 15:601.
  15. Seller MJ. Recurrence risks for neural tube defects in a genetic counseling clinic population. J Med Genet 1981; 18:245.
  16. Czeizel A, Métneki J. Recurrence risk after neural tube defects in a genetic counselling clinic. J Med Genet 1984; 21:413.
  17. Koch M, Fuhrmann W. Sibs of probands with neural tube defects--a study in the Federal Republic of Germany. Hum Genet 1985; 70:74.
  18. Nussbaum R, McInnes RR, Willard HF. Genetics of disorders with complex inheritance. In: Thompson & Thompson Genetics in Medicine, 6, WB Saunders, Philadelphia 2001. p.289.
  19. MacCarthy PA, Dalrymple IJ, Duignan NM, et al. Recurrence rates of neural tube defects in Dublin maternity hospitals. Ir Med J 1983; 76:78.
  20. Copp AJ, Greene ND. Genetics and development of neural tube defects. J Pathol 2010; 220:217.
  21. Mazzitelli N, Vauthay L, Grandi C, et al. Reviewing old concepts at the start of a new millenium: growth restriction, adrenal hypoplasia, and thymomegaly in human anencephaly. Teratology 2002; 66:105.
  22. Sadovnick AD, Baird PA. Congenital malformations associated with anencephaly in liveborn and stillborn infants. Teratology 1985; 32:355.
  23. Mathew A. Anencephaly-associated aganglionosis. Am J Med Genet 1998; 80:518.
  24. Peabody JL, Emery JR, Ashwal S. Experience with anencephalic infants as prospective organ donors. N Engl J Med 1989; 321:344.