Hereditary subependymal heterotopia associated with mega cisterna magna: antenatal diagnosis with magnetic resonance imaging

A practical approach to prenatal diagnosis of malformations of cortical development

Malformations of cortical development (MCD) can frequently be diagnosed at multi-disciplinary Fetal Neurology clinics with the aid of multiplanar neurosonography and MRI. The patients are usually referred following prenatal sonographic screening that raises the suspicion of a possible underlying MCD. These indirect findings include, but are not limited to, ventriculomegaly (lateral ventricles larger than 10 mm), asymmetric ventricles, commissural anomalies, absent cavum septum pellucidum, cerebellar vermian and/or hemispheric anomalies, abnormal head circumference (microcephaly or macrocephaly), multiple CNS malformations, and associated systemic defects. The aim of this paper is to suggest a practical approach to prenatal diagnosis of malformations of cortical development utilizing dedicated neurosonography and MRI, based on the current literature and our own experience. We suggest that an MCD should be suspected in utero when the following intracranial imaging signs are present: abnormal development of the Sylvian fissure; delayed achievement of cortical milestones, premature appearance of sulcation; irregular ventricular borders, abnormal cortical thickness (thick, thin); abnormal shape and orientation of the sulci and gyri; irregular, abnormal, asymmetric, and enlarged hemisphere; simplified cortex; non continuous cortex or cleft; and intraparenchymal echogenic nodules. Following the putative diagnosis of fetal MCD by neurosonography and MRI, when appropriate and possible (depending on gestational age), the imaging diagnosis is supplemented by genetic studies (CMA and trio whole exome sequencing). In some instances, no further studies are required during pregnancy due to the clear dire prognosis and then the genetic evaluation can be deferred after delivery or termination of pregnancy (in countries where allowed).

Prenatally diagnosed periventricular nodular heterotopia: Further delineation of the imaging phenotype and outcome

OBJECTIVES

Periventricular nodular heterotopia (PNH) is a malformation of cortical development which presents with heterogeneous imaging, neurological phenotype and outcome. There is a paucity of comprehensive description detailing the prenatal diagnosis of PNH. The aim of this study is to report neuroimaging features and correlated outcomes in order to delineate the spectrum of prenatally diagnosed PNH.

METHODS

It was a retrospective study over 15 years in five tertiary centers. All fetuses with prenatally diagnosed PNH were collected. Fetal ultrasound and MRI were reviewed and genetic screening collected. Prenatal findings were analyzed in correlation to fetopathological analyses and post-natal follow up.

RESULTS

Thirty fetuses (22 females and 8 males) with PNH were identified. The two major ultrasound signs were ventriculomegaly associated with dysmorphic frontal horns (60%) and posterior fossa anomalies (73.3%). On MRI, two groups of PNH were identified: the contiguous and diffuse PNH (n = 15, 50%), often associated with megacisterna magna, and the non-diffuse, either anterior, posterior or unilateral PNH. FLNA mutations were found in 6/11 cases with diffuse PNH. Additional cortical malformations were exclusively observed in non diffuse PNH (9/15; 60%). Twenty-four pregnancies (80%) were terminated. Six children aged 6 months to 5 years are alive. Five have normal neurodevelopment (all had diffuse PNH) whereas one case with non diffuse PNH has developmental delay and epilepsy.

CONCLUSION

PNH is heterogeneous but patients with diffuse PNH are a common subgroup with specific findings on prenatal imaging and implications for prenatal counseling.

Prenatal diagnosis of periventricular nodular heterotopia in borderline ventriculomegaly using sonography and magnetic resonance imaging

Periventricular nodular heterotopia (PNH) is usually missed on prenatal sonographic examinations, even on targeted scans. Irregular ventricular walls on axial view and irregular square-shaped lateral ventricles on coronal view are suggestive of PNH in the early third trimester. To achieve an early prenatal diagnosis, it is important to keep in mind the possible coexistence of PNH with brain malformations such as ventriculomegaly, posterior fossa anomalies, or agenesis of corpus callosum. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:510-513, 2016.

Malformations of Cortical Development: From Postnatal to Fetal Imaging

Abnormal fetal corticogenesis results in malformations of cortical development (MCD). Abnormal cell proliferation leads to microcephaly or megalencephaly, incomplete neuronal migration results in heterotopia and lissencephaly, neuronal overmigration manifests as cobblestone malformations, and anomalous postmigrational cortical organization is responsible for polymicrogyria and focal cortical dysplasias. MCD comprises various congenital brain disorders, caused by different genetic, infectious, or vascular etiologies and is associated with significant neurological morbidity. Although MCD are rarely diagnosed prenatally, both dedicated multiplanar neurosonography and magnetic resonance imaging enable good demonstration of fetal cortical development. The imaging signs of fetal MCD are: delayed or absent cerebral sulcation; premature abnormal sulci; thin and irregular hemispheric parenchyma; wide abnormal overdeveloped gyri; wide opening of isolated sulci; nodular bulging into the lateral ventricles; cortical clefts; intraparenchymal echogenic nodules; and cortical thickening. The postnatal and prenatal imaging features of four main malformations of cortical development—lissencephaly, cobblestone malformations, periventricular nodular heterotopia, and polymicrogyria—are described.

Prenatal diagnosis of frontonasal dysplasia associated with bilateral periventricular nodular heterotopia

Frontonasal dysplasia is an etiologically heterogeneous development alteration including a set of anomalies affecting the eyes, forehead, and nose as a result of a malformation of the frontonasal elevation. It could occur either in isolation or as part of a syndrome such as frontonasal dysplasia associated with periventricular heterotopia. Our goal is to document the first clinical case of prenatal diagnosis for frontonasal dysplasia associated with periventricular heterotopia by fetal magnetic resonance imaging (MRI) at weeks 19.5 and 29 and postnatal MRI. In conclusion, the presence of frontonasal dysplasia in a prenatal ultrasonography should always be followed by a fetal MRI with routine screening for periventricular nodular heterotopias so as to establish a more adequate prognosis for the family.

Periventricular nodular heterotopia on prenatal ultrasound and magnetic resonance imaging

OBJECTIVES

To describe the prenatal ultrasound and magnetic resonance imaging (MRI) findings suggestive of periventricular nodular heterotopia (PNH).

METHODS

This retrospective case series included fetuses referred to our institution for brain MRI between 2007 and 2012, which were diagnosed with PNH and confirmed by postnatal MRI or autopsy. The type of PNH, associated ventriculomegaly and associated malformations are reported.

RESULTS

We included 11 fetuses (nine female, two male) with a mean gestational age at diagnosis of 31 (range, 23-34) weeks. PNH lesions were small and diffuse (n = 7), large and multiple (n = 1) or single (n = 3). A targeted ultrasound examination performed before fetal MRI missed the diagnosis in four cases (one diffuse and three single); a further ultrasound examination performed after MRI diagnosed PNH in two of these four cases. Ventriculomegaly was present in six cases (four unilateral and two bilateral). PNH appeared in all cases as nodules of intermediate echogenicity protruding into the ventricular lumen. In all cases of diffuse PNH, the frontal horns and bodies of the lateral ventricles appeared square in shape on coronal view, with irregular borders on axial view. Associated cerebral malformations were observed in seven cases and included corpus callosal agenesis (n = 4, with additional malformations in two) and retrocerebellar cyst (n = 3). Extracerebral malformations were also present in two cases. Maternal MRI was performed in five of the six cases of isolated small and diffuse PNH in female fetuses, and demonstrated PNH in two of these.

CONCLUSION

PNH is underdiagnosed at prenatal ultrasound, even on targeted scans. Irregular ventricular borders on axial view and irregular square-shaped lateral ventricles on coronal view are suggestive of PNH at prenatal ultrasound.

Periventricular heterotopia: new insights into Ehlers-Danlos syndrome

Nature often employs similar mechanisms to complete similar tasks, thus the evolution of homologous proteins across various organ systems to perform similar but slightly different functions. In this respect, disorders attributed to specific genetic mutations, while initially thought to be restricted in function and purpose, may provide broad insight into general cellular and molecular mechanisms of development and maintenance. One such example can be seen in the brain malformation, periventricular heterotopia (PH), which is characterized by very specific nodules of neurons that line the lateral ventricles beneath the cerebral cortex. PH is seen as a disorder of neuronal migration and can be caused by mutations in filamin A (FLNA), which encodes an actin-binding protein that regulates the cytoskeleton and cell motility. Recent advances in our understanding of the genetic causes of PH suggest that mutations in this gene, however, are also associated with the connective tissue disorder, Ehlers-Danlos syndrome (EDS), in which affected individuals present with joint and skin hyperextensibility and vascular problems including aortic dissection, excessive bleeding and bruisability. While much still remains unknown regarding the mechanistic role of FLNA in giving rise to PH and EDS, a common cellular and molecular basis likely gives rise to these two seemingly unrelated clinical disorders.

Prenatal diagnosis of herniated Dandy-Walker cysts

OBJECTIVE

The purpose of this series is to describe the prenatal diagnosis and pregnancy outcome of fetuses affected with Dandy-Walker malformation in which a posterior cyst herniated through a bony defect of the occipital skull, foramen magnum, or both.

METHODS

Two- and 3-dimensional sonography were used to examine 2 fetuses with poorly delineated cerebellar structures and a large posterior cystic neck mass. Fetal magnetic resonance imaging (MRI) was added to this evaluation as a complementary diagnostic modality.

RESULTS

Three-dimensional sonography helped characterize the precise site of cyst herniation through the occipital skull or foramen magnum. Fetal MRI confirmed the sonographic findings. Neonatal MRI studies identified heterotopic gray matter as evidence of a neuronal migration disorder in both fetuses. The second fetus also had agenesis of the corpus callosum. Retrospective review of the fetal MRI (25.9 weeks' menstrual age) and 3-dimensional sonographic (18.7 weeks' menstrual age) studies confirmed ventricular wall nodularity involving the occipital horns of the second fetus.

CONCLUSIONS

The antenatal detection of a large posterior cystic neck mass and a poorly defined or nonvisualized cerebellar vermis suggest Dandy-Walker malformation with a herniated cyst. Three-dimensional sonography and fetal MRI are important adjunctive methods that can be used to evaluate the herniation site and a possible neuronal migrational disorder.

Clinical features and long term outcome of epilepsy in periventricular nodular heterotopia. Simple compared with plus forms

OBJECTIVES

Little is known about the long term outcome of patients with periventricular nodular heterotopia (PNH) and epilepsy, particularly the course of seizures. This study investigated the electroclinical and prognostic features of 16 patients with PNH.

METHODS

Of 120 patients with epilepsy and malformations of cortical development, 16 had PNH. Of these, eight patients had periventricular nodules only (simple PNH) and eight also presented with other cortical or cerebral malformations (subcortical heterotopia; polymicrogyria; focal dysplasia; schizencephaly; cortical infolding; agenesis of the corpus callosum; mega cisterna magna and cerebellar atrophy) (PNH plus). All patients underwent clinical, neurophysiological, and MRI investigation. The mean follow up was 17.3 years (2-40 years).

RESULTS

Two electroclinical patterns emerged: (1) The first pattern, associated with simple PNH, was characterised by normal intelligence and seizures, usually partial, which began during the second decade of life. The seizures never became frequent and tended to disappear or become very rare. The EEG showed focal abnormalities. (2) The second pattern, associated with PNH plus, was characterised by mental retardation and seizures that began during the first decade of life. The seizures were very frequent in most cases and sudden drops were observed in six patients. Seizures were medically refractory in four patients. The EEG showed focal and bisynchronous abnormalities.

CONCLUSIONS

Two groups of PNH patients with different electroclinical and neuroradiological features can be identified after a long term follow up. The presence of other types of cortical or cerebral malformations, in addition to periventricular nodules, determines a poor prognosis.