hidranensefal

Prenatal Sonography in HydranencephalyFindings During the Early Stages of Disease

ydranencephaly is a severe, sporadic brain abnormality char-acterized by absence of the cerebral hemispheres, which arereplaced by a large supratentorial fluid-filled saclike struc-

ture surrounding the brain stem.1,2 This condition is thought to bethe result of extensive brain necrosis secondary to a vascular insultinvolving the internal carotid arteries, which occurs after the brainand ventricles have been fully formed.1,2 Prenatal diagnosis of hy-dranencephaly is usually made in the second or third trimester ofpregnancy, at which time the most striking sonographic findings in-clude the detection of a brain cavity filled with anechoic fluid andpreservation of the brain stem and posterior fossa structures.3

Because of the rarity of this disorder, almost all descriptions ofthe prenatal diagnosis of this condition are based on single case re-ports in fetuses presenting remote from the episode of cerebralstroke. In a few cases, serial scans illustrating the prenatal evolutionare available,4–6 all demonstrating different sonographic features atpresentation, including the identification of an admixture of dense

Waldo Sepulveda, MD, Hernan Cortes-Yepes, MD, Amy E. Wong, MD, Victor Dezerega, MD,Edgardo Corral, MD, Gustavo Malinger, MD

Received September 19, 2011, from the FetalMedicine Center, Fetal Medicine Interest Group(GIMEF), Santiago, Chile (W.S., A.E.W., V.D.,E.C.); Maternal-Fetal Medicine Unit, HospitalUniversitario San Vicente de Paul, Universidad deAntioquia, Medellin, Colombia (H.C.-Y.); andFetal Neurology Clinic, Department of Obstet-rics and Gynecology, Wolfson Medical Center,Holon, Israel (G.M.). Revision requested October10, 2011. Revised manuscript accepted for publi-cation November 30, 2011.

This work was supported by an unrestrictedresearch grant from the Sociedad Profesional deMedicina Fetal “Fetalmed” Limitada, Chile.

Address correspondence to Waldo Sepul-veda, MD, Fetal Medicine Center, Casilla 208,Santiago 20, Chile.

E-mail [email protected]

H

©2012 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2012; 31:799–804 | 0278-4297 | www.aium.org

CASE SERIES

The purpose of this report is to describe the prenatal sonographic findings in fetuseswith hydranencephaly diagnosed during the early stages of disease. Four cases withcharacteristics of hydranencephaly were retrospectively identified from 2 Latin Amer-ican fetal medicine referral centers. Information on maternal demographics, sonographicfindings, antenatal courses, and pregnancy outcomes was retrieved from the ultrasoundreports and medical records. Cases were diagnosed between 21 and 23 weeks’ gestation.The sonographic findings were similar in all cases and included absent cerebral hemi-spheres, which were replaced by homogeneous echogenic material filling the supra-tentorial space, and preservation of the thalami, brain stem, and cerebellum. The headcircumference measurement was within the normal range, but the transverse cerebel-lar diameter was below the fifth percentile in 3 of the 4 cases. A follow-up scan in 1 ofthese cases demonstrated the classic anechoic fluid-filled appearance of hydranen-cephaly 2 weeks after diagnosis. Confirmation of the diagnosis was available in 2 cases,by postmortem examination in 1 and by fetal magnetic resonance imaging in the other.No further investigations were performed in the 2 women who opted for terminationof pregnancy. In conclusion, during the early stages of disease, hydranencephaly is char-acterized by the presence of a large intracranial saclike structure containing homoge-neous echogenic material, representing blood and necrotic debris secondary to massiveliquefaction of the developing cerebral hemispheres.

Key Words—cerebral ischemia; fetal sonography; fetus; hydranencephaly; intracranialhemorrhage; prenatal diagnosis

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hemorrhagic and necrotic tissue,4 organized blood clotsreplacing the cerebral hemispheres,5 and an echoic intra -cranial cyst in the early second trimester.6 The aim of thisreport was to present our experience with the clinical andprenatal sonographic findings in cases of hydranencephalydiagnosed during the early stages of disease.

Materials and Methods

The protocol for this retrospective study was approved bythe corresponding Institutional Review Boards. We iden-tified 4 cases with similar appearances thought to repre-sent hydranencephaly, all diagnosed during the secondtrimester of pregnancy at 2 Latin American fetal medicinereferral centers. Information on maternal demographics,prenatal sonographic findings, antenatal courses, and preg-nancy outcomes was obtained from the medical records,ultrasound reports, and referring obstetricians.

Results

The most relevant clinical and sonographic findings in ourcases are presented in Table 1. The gestational age at thetime of the diagnosis varied from 21 to 23 weeks. Twowomen were referred after their routine second-trimesterscan showed a fetal brain abnormality in otherwise unre-markable pregnancies, although 1 of these patients had a

history of drug abuse. The other 2 cases were diagnosed atthe time of emergency obstetric consultation (late miscar-riage in 1 and failed abortion with misoprostol and a sub-sequent suicide attempt with carbamate pesticide in theother). Two women were primigravidas, and 2 were mul-tiparous with prior uncomplicated term pregnancies. Noneof patients had a previous early second-trimester scan inthe current pregnancy.

Representative images from our cases are presentedin Figures 1–3. Invariably, the most striking finding at pres-entation was the absence of cerebral hemispheres, whichwere replaced by homogeneous echogenic material fillingalmost all of the supratentorial space. In addition, it waspossible to identify the cerebellum, thalami, brain stem,and portions of the choroid plexuses and the cerebral falxin all cases. The size of the fetal head, as determined byhead circumference measurement, was within the normalrange in all cases, whereas the transverse cerebellar diam-eter was below the fifth percentile for gestational age in 3 ofthe 4 cases.7 Color flow imaging revealed the presence ofthe circle of Willis in only 1 case. No associated extracranialabnormalities were detected by prenatal sonography in anyof the cases.

Regarding pregnancy outcomes, 2 women underwenttermination of pregnancy; 1 miscarried a stillborn neonateshortly after the scan; and 1 delivered at term with subse-quent early neonatal death. In the ongoing pregnancy, a

Sepulveda et al—Prenatal Sonography in Hydranencephaly

J Ultrasound Med 2012; 31:799–804800

Table 1. Fetal Hydranencephaly: Clinical Cases

Case MA, y Parity Reason for Referral GA, wk HC, mm TCD, mm Sonographic Findings Remarks

1 17 0 Abnormal fetal brain 23 212 18a Absent cerebral hemispheres; Drug abuse, TOP

at second-trimester homogeneous material filling

scan the supratentorial space, normal

appearance of the cerebellum

and brain stem, portions of the

choroid plexuses and the cerebral

falx identified

2 19 0 Abnormal fetal brain 21 173 18a Same as in case 1 plus posterior Term delivery, early

at second-trimester aspect of the occipital cortex neonatal death

scan visible

3 28 2 Threatened miscarriage, 21 196 21 Same as in case 1 plus remnants Miscarriage, post-

suspicion of holoprosen- of lateral ventricles, circle of Willis mortem exam-

cephaly present ination confirmed

prenatal findings

4 25 2 Suicide attempt 23 218 20a Same as in case 1 plus remnants Abortion attempt at

of lateral ventricles 20 wk, suicide

attempt at 23 wk,

TOP

GA indicates gestational age; HC; head circumference; MA, maternal age; TCD, transverse cerebellar diameter; and TOP; termination of pregnancy.aValues below the fifth percentile according to gestational age.7


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Figure 1. Case 2. A and B, Axial and sagittal views of the fetal head at 21 weeks’ gestation. There is homogeneous echogenic material replacing the

cerebral hemispheres. Note preservation of the thalami and cerebellum. C, Axial view of the fetal head at 23 weeks’ gestation shows anechoic fluid

filling the supratentorial space. Part of the posterior aspect of the occipital lobe is visualized. D, Sonographic view of the posterior fossa shows preser-

vation of the cerebellum and cisterna magna. Both choroid plexuses and the cerebral falx are identified. E, Magnetic resonance imaging at 32 weeks.

Sagittal and coronal views confirm the diagnosis of hydranencephaly.

A B

C D

E



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A

D

B

E

C

Figure 2. Case 3. A and B, Coronal views of the fetal head at 21 weeks

show dense, homogeneous material filling the supratentorial space.

Portions of the cerebral falx and choroid plexuses are identified. C, Color

flow imaging shows the patent basilar vessels feeding structures of the

posterior fossa. D, The circle of Willis is visualized. E, Postmortem spec-

imen shows absent cerebral hemispheres and preservation of the

cerebellum and portions of the occipital cortex. The cerebral falx is also

identified.


follow-up scan revealed the characteristic finding of an ane-choic fluid-filled intracranial cavity 2 weeks after the diag-nosis was made. Confirmation of the diagnosis wasavailable in 2 cases, by magnetic resonance imaging at 32weeks in 1 case and by postmortem examination in theother. No further investigations were performed in the 2women who opted for termination of pregnancy.

Discussion

Hydranencephaly represents the most severe form of cor-tical destruction. It usually occurs in the fetal period buthas also been reported in young children.8 The exact eti-ology is unclear, although the most accepted hypothesis isacute bilateral occlusion of the internal carotid arteries,with abrupt lack of a blood supply to the brain, leading tomassive tissue necrosis and hemorrhage of the developingcerebral cortex.1–3 A similar pattern of anomalies was re-produced in animal models following ligation of bothcarotid arteries and jugular veins.9,10 The traditional pre-natal sonographic findings include absence of the cerebralhemispheres and their replacement by a large anechoicfluid-filled intracranial space.3 In early stages of disease,however, the intracranial contents show uniform low-levelechogenicity likely due to liquefied cerebral structures andblood, with a similar appearance to that of endometriomafluid. This particular feature, noted in all of our cases, hasbeen described only once previously in a report publishedmore than 25 years ago.4 Another pathognomonic featureof hydranencephaly is the preservation of brain stem andposterior fossa structures,1–3 as seen in all of our cases. This finding is also explained by the perfusion of this areaof the brain by the vertebral-basilar arterial system, whichpartially protects these lower midline structures from thevascular insult affecting the territory of the internal carotidarteries.1,2 Nevertheless, the visualization of the circle ofWillis in 1 of our cases demonstrates that, at least in somecases, the internal carotid arteries could remain patent, andocclusion of the cerebral branches distal to the circle ofWillis can occasionally lead to similar pathophysiologicevents ending in massive brain destruction. Of note, thefetal head circumference was normal in all cases, but thecerebellum was noted to be hypoplastic in all but the casein which the circle of Willis was patent.

Main differential diagnoses that should be consideredinclude severe hydrocephaly, alobar holoprosencephaly,and extreme forms of porencephaly and schizencephaly.3In severe hydrocephaly, however, an intact rim of cortexsurrounding the enlarged cerebral ventricles is always vi-sualized. Distinguishing features of holoprosencephaly in-

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Figure 3. Case 4. A, Axial view of the head shows dense, homogeneous

material in the brain cavity. The cerebral falx is also identified in this view.

B, In a lower transverse section, portions of the lateral ventricles and

choroid plexuses are identified. C, Section through the posterior fossa

shows a small cerebellum.

A

B

C


clude microcephaly and fused thalami in association withfacial abnormalities. In extensive forms of destructiveprocesses such as porencephaly and schizencephaly, thereare large areas of the brain in which normal cerebral tissueis identified. Another condition is Fowler syndrome, a rareautosomal recessive condition characterized by severe cor-tical atrophy and progressive destruction of central nervoussystem tissue due to a proliferative vasculopathy, leadingto early fetal akinesia and arthrogryposis.11 As demon-strated by our cases, the sonographic appearances of hy-dranencephaly during the early stages of disease would beconsistent with acute destruction of the cerebral cortex,giving it a characteristic homogeneously echogenic patternwithin the cranial cavity representing blood and necroticdebris. Over time, this content is progressively replaced bymore anechoic fluid as the result of progressive liquefac-tion of blood clots and brain tissue and continued produc-tion of cerebrospinal fluid by the choroid plexuses, leadingto the classic sonographic appearance of hydranencephalyas seen at the end stages of disease.1–3

Regarding the pathophysiologic mechanism, vascularocclusion may be triggered by local phenomena, such asthrombosis, necrotizing vasculitis, and proliferative vascu-lopathy, or acute vasoconstrictive events secondary to in-fection or toxic exposure.11,12 In the 2 of our 4 cases inwhich maternal substances abuse was known, it is possiblethat hydranencephaly occurred after the consumption ofdrugs known to produce encephaloclastic destruction,neurotoxicity, or vascular dysruption.13–15 The other 2women denied the use of any of illicit or toxic substances.Nevertheless, if substance use would be associated with hydranencephaly, the reason why only some fetuses exposed to these teratogenic drugs develop the disease andnot others remains to be elucidated.

References

1. Romero R, Pilu G, Jeanty P, Ghidini A, Hobbins JC. Hydranencephaly. In:Prenatal Diagnosis of Congenital Anomalies. Norwalk, CT: Appleton &Lange; 1998:52–54.

2. Bianchi DW, Crombleholme TM, D’Alton ME, Malone FD. Hydra-nencephaly. In: Fetology: Diagnosis and Management of the Fetal Patient. NewYork NY: McGraw-Hill; 2010:130–133.

3. Kurtz AB, Johnson PT. Diagnosis please. Case 7: hydranencephaly. Radiology 1999; 210:419–422.

4. Greene MF, Benacerraf B, Crawford JM. Hydranencephaly: US appear-ance during in utero evolution. Radiology 1985; 156:779–780.

5. Edmondson SR, Hallak M, Carpenter RJ, Cotton DB. Evolution ofhydranencephaly following intracerebral hemorrhage. Obstet Gynecol1992; 75:870–871.

6. Lam YH, Tang MHY. Serial sonographic features of a fetus with hydra-nencephaly from 11 weeks to term. Ultrasound Obstet Gynecol 2000;16:77–79.

7. Snijders RJM, Nicolaides KH. Fetal biometry at 14–40 weeks’ gestation.Ultrasound Obstet Gynecol 1994; 4:34–48.

8. Lindenberg R, Swanson PD. “Infantile hydranencephaly”: a report of fivecases of infarction of both cerebral hemispheres in infancy. Brain 1967;90:839–850.

9. Myers RE. Brain pathology following fetal vascular occlusion: an experi-mental study. Invest Ophthalmol 1969; 8:41–50.

10. Wintour EM, Lewitt M, McFarlane A, et al. Experimental hydranen-cephaly in the ovine fetus. Acta Neuropathol 1996; 91:537–544.

11. Williams D, Patel C, Fallet-Bianco C, et al. Fowler syndrome: a clinical,radiological, and pathological study of 14 cases. Am J Med Genet 2010;152A:153–160.

12. Govaert P. Prenatal stroke. Semin Fetal Neonatal Med 2009; 14:250–266.13. Rais-Bahrami K, Naqvi M. Hydranencephaly and maternal cocaine use:

a case report. Clin Pediatr 1990; 29:729–730.14. Philip NM, Shannon C, Winikoff B. Misoprostol and teratogenicity:

reviewing the evidence. In: Critical Issues in Reproductive Health. New York,NY: Population Council; 2003.

15. Costa LC, Giordano G, Guizzetti M, Vitalone A. Neurotoxicity of pesti-cides: a brief review. Front Biosci 2008; 13:1240–1249.


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