Elsevier

Pediatric Neurology

Volume 48, Issue 2, February 2013, Pages 152-158
Pediatric Neurology

Case Report
Looking at the Missing Brain: Hydranencephaly Case Series and Literature Review

https://doi.org/10.1016/j.pediatrneurol.2012.10.009Get rights and content

Abstract

Hydranencephaly is a severe congenital condition where most of the cerebral hemispheres are replaced by a membranous sac. Despite the growing amount of case reports, most pathogenic, phenotypic, and prognostic aspects of hydranencephaly remain controversial. By matching the recent literature data with the findings of our own series (four cases: two fetuses at the twelfth gestational week, a 32-year-old man, and a 14-year-old female), we attempted to date back the insult leading to hydranencephaly to understand its pathogenesis and to explain the basis of its protean phenotype. The variable detection of cerebral remnants seems to mirror the developmental pathway of cerebral arteries. Moreover, fetal and postnatal neuroimaging data and histopathologic findings point toward an early bilateral internal carotid artery occlusion, mostly occurring between the eighth and twelfth gestational weeks, as the main pathogenic mechanism of hydranencephaly.

Introduction

Hydranencephaly is an uncommon disorder of the central nervous system characterized by a massive hemispheric necrosis and extreme ventricular dilation, with most of the hemispheres replaced by a membranous sac, and relative preservation of the diencephalic and posterior cranial fossa brain structures [1]. Despite the increasing evidence from ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and histopathologic and clinical data, several aspects of hydranencephaly remain controversial in terms of pathogenesis, time of onset, spectrum of phenotypic presentation, and prognosis.

Whatever the cause (infectious, toxic, iatrogenic, genetic, etc.), brain damage is believed to result from early severe bilateral internal carotid artery compromise [2]. Indeed, postnatal angiographic studies often disclosed internal carotid artery abnormalities ranging from hypoplasia to aplasia [3], [4] with brain involvement usually reflecting internal carotid artery supply distribution.

The putative time of internal carotid artery involvement during fetal life is unclear because of the wide variability of prenatal or postnatal age at which hydranencephaly is diagnosed. Histologic studies provided interesting though contradictory hints to understand the timing of internal carotid artery involvement by showing at which level brain maturation had been interrupted [5], [6]. The introduction of routine ultrasound fetal investigation in the first trimester has determined an earlier detection of hydranencephaly, thus challenging previous hypotheses situating the onset in the second trimester of gestation.

Regarding gross pathologic study, the extensive replacement of brain matter with cerebrospinal fluid and the preservation of diencephalic/posterior cranial fossa structures are the hallmarks of hydranencephaly. However, many reports demonstrated the frequent persistence of occipital, temporal, or frontal cerebral remnants. The variability of brain involvement further challenges the idea of a common pathogenic mechanism and highlights the need to understand better early intracranial vascular development. Most newborns with hydranencephaly have reduced life expectancy and die within a few weeks or months after birth; however, the survival length range is extremely wide [7], with exceptional cases surviving until the third decade.

We report on two fetuses and two young patients with prenatally acquired hydranencephaly and review the recent literature in English. The radiologic and neuropathologic data are presented, and the likely underlying pathogenesis, including the timing of the noxious event, is discussed.

Section snippets

Patient 1

A 27-year-old healthy Caucasian woman was referred for routine prenatal diagnosis at the twelfth week of gestation. She had a previous miscarriage in the eleventh week of gestation. Test results for toxoplasma, rubella, cytomegalovirus, and herpes simplex (TORCH) infections were negative. The patient had no family history of genetic disorders and had not been not exposed to teratogenic or radioactive agents during the first weeks of pregnancy. Ultrasound examination revealed a single live fetus

Review of the literature

A research of the literature published in English from January 2000 to May 2012 was conducted by use of the Medline database (PubMed.gov; U.S. National Library of Medicine–National Institutes of Health) with “hydranencephaly” used as a key word. All articles on human beings were analyzed, and further studies were identified by reviewing reference lists from selected studies and reviews. Studies on subjects affected with conditions different from hydranencephaly (e.g., holoprosencephaly or

Discussion

We reported on four cases of hydranencephaly: two of them, with triploidy, were diagnosed in the first trimester of gestation and underwent termination of pregnancy; one patient died during abdominal surgery at the age of 13 and had histopathologic brain evaluation; the last patient is a long-term survivor of 32 years of age. Since its first description by Cruveilhier in 1835, much debate has arisen about the pathogenesis of hydranencephaly. Several predisposing conditions have been identified,

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    Both authors contributed equally to this work and should be considered fist authors.

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