What causes Hydranencephaly?

This is a great and often asked question.  Unfortunately I don’t believe that there is a clear cause. 

Obviously there are a variety of causes. 

I’m including here some summaries of research projects I’ve found on the Internet.

  1. Association of prenatal vascular disruptions with decreased maternal age. (Am J Med Genet 1997 Mar 31;69(3):237-9 Lubinsky MS Department of Pediatrics, Medical College of Wisconsin, Milwaukee, USA.)
Disruptions of fetal structures can create a variety of congenital anomalies. Some apparent prenatal vascular disruptions associate strongly with decreased maternal age, and are rare with older mothers. This is well-documented for gastroschisis, (A birth defect in which there is a separation in the abdominal wall. Through this opening protrudes part of the intestines which are not covered by peritoneum (the membrane that normally lines the inside of the abdomen). Definition from Medicinenet.com) but similar findings with hydranencephaly suggest a general phenomenon that may also involve porencephaly, septo-optic dysplasia, early body stalk disruptions, certain hemifacial anomalies, and other findings. Prenatal vascular disruption may be a common cause of congenital anomalies, but its nature is unknown, and obvious environmental confounders associated with decreased maternal age may have only relatively small contributions. A protective effect for pregnancies of older mothers also remains a possibility.

2. Decreased maternal age with hydranencephaly (Am J Med Genet 1997 Mar 31;69(3):232-4 Lubinsky MS, Adkins W, Kaveggia EG
Department of Pediatrics, Medical College of Wisconsin, Milwaukee, USA.)

We studied parental ages of institutionalized children with hydranencephaly. Mothers under age 20 years and under age 18 years were, respectively, 5 and 10 times as frequent as in the general population, and 3 and 4 times more frequent than for institutionalized control patients. Unwed mothers were also common, but may reflect high rates in younger mothers combined with institutionalization bias. Thus, hydranencephaly appears to show a decreased maternal age effect, similar to that seen with other conditions presumably due to prenatal vascular disruptions. (PMID: 9096748, UI: 97251065 )

  Contrary to what is stated in this study our experience has had different results.  
Our results were:

From the Swiss Society of Neonatology
Hydranencephaly is a rare condition defined as extensive destruction of the brain caused by disruption of brain perfusion. The normal brain tissue is replaced by a membranous sac which is filled with fluid.¹ In a series of 4122 autopsies, 363 cases revealed some congenital CNS malformation (235 liveborn infants and 128 stillborn infants), but hydranencephaly was diagnosed in only two patients.²

Disruptions affect mainly the major vessels of the anterior and middle cerebral arteries. Up to the 20^th week of gestation neuronal migration is still active. The earlier disruptions occur in the second trimester, the more migrational disorganisation may be found. After 20 weeks of gestation, the brain lesions are not accompanied by cytoarchitectural disorders. During this midgestational period, the neural tube is already closed and well developed. Intact skull and scalp are covering the underlying central nervous system structures and the head appears normal.
Fetal cerebral perfusion can be affected by A) maternal conditions (cardiovascular collapse; trauma; gas poisoning; coagulopathy; cocaine abuse), B) fetal conditions (multiple pregnancy; non-immune hydrops fetalis; blood dyscrasia), or C) placenta and cord pathologies (infarct; calcifications; knot of the cord; neoplasm).³

In surviving infants, neuromotor activity is very limited with some patients developing uncoordinated movements. Convulsions are rarely described because of the absence of a motor cortex in most patients*. The sensory capacities are also very limited with some reaction to strong light. In very rare cases, crying and smiling may be seen.

Prolonged survival of up to 19 years can occur with hydranencephaly; it is, however, not associated with any improvements in consciousness or awareness.⁴ Electrophysioogic features cannot be used as predictors of the length of survival, whereas some authors have suggested a functioning hypothalamic-pituitary-adrenal axis to be essential for prolonged survival.

* Please note: according to our survey of 81 children with Hydranencephaly 75% of the children have seizures. However they are usually brain stem seizures (see p. for more information)

Antepartum fetal intracranial hemorrhage, predisposing factors and prenatal sonography: a review. Sherer DM, Anyaegbunam A, Onyeije C

(PMID: 9759911, UI: 98430711)

Here’s an interesting article

  Hemihydranencephaly: case report and literature review.
Greco F, Finocchiaro M, Pavone P, Trifiletti RR, Parano E.
Department of Pediatrics, University of Catania, Italy.

Hydranencephaly is a severe brain condition characterized by complete or almost complete absence of cerebral cortex with preservation of meninges, basal ganglia, pons, medulla, cerebellum, and falx. It has been ascribed to different causes (infections, irradiations, fetal anoxia, medications, twin-twin transfusion), all leading to vascular disruption. Hemihydranencephaly is an extremely rare condition in which the vascular anomaly is unilateral. We report on a patient who was suspected to have hydrocephalus in utero; a brain magnetic resonance imaging scan showed left-sided hydranencephaly with preservation of basal ganglia. The patient developed signs of right hemiparesis but notably has only mild language delay. The available literature on hemihydranencephaly is reviewed.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11305691&dopt=Abstract

Cause of Hydranencephaly: print friendly version