Aicardi syndrome, an unsolved mystery: Review of diagnostic features, previous attempts, and future opportunities for genetic examination

Hyaline protoplasmic astrocytopathy in epilepsy

Hyaline protoplasmic astrocytopathy (HPA) describes a rare histologic finding of eosinophilic, hyaline cytoplasmic inclusions in astrocytes, predominantly in the cerebral cortex. It has mainly been observed in children and adults with a history of developmental delay and epilepsy, frequently with focal cortical dysplasia (FCD), but the nature and significance of these inclusions are unclear. In this study, we review the clinical and pathologic features of HPA and characterize the inclusions and brain tissue in which they are seen in surgical resection specimens from five patients with intractable epilepsy and HPA compared to five patients with intractable epilepsy without HPA using immunohistochemistry for filamin A, previously shown to label these inclusions, and a variety of astrocytic markers including aldehyde dehydrogenase 1 family member L1 (ALDH1L1), SRY-Box Transcription Factor 9 (SOX9), and glutamate transporter 1/excitatory amino acid transporter 2 (GLT-1/EAAT2) proteins. The inclusions were positive for ALDH1L1 with increased ALDH1L1 expression in areas of gliosis. SOX9 was also positive in the inclusions, although to a lesser intensity than the astrocyte nuclei. Filamin A labeled the inclusions but also labeled reactive astrocytes in a subset of patients. The immunoreactivity of the inclusions for various astrocytic markers and filamin A as well as the positivity of filamin A in reactive astrocytes raise the possibility that these astrocytic inclusions may be the result of an uncommon reactive or degenerative phenomenon.

A case of Aicardi syndrome associated with duplication event of Xp22 including SHOX

BACKGROUND

Aicardi syndrome is a neurodevelopmental disorder characterized by a triad of partial or complete agenesis of the corpus callosum, infantile spasms, and pathognomonic chorioretinal lacunae.

METHODS

Examination, multimodal imaging, and genetic testing were used to guide diagnosis.

RESULTS

We report a case of a pediatric patient who was initially diagnosed with refractory infantile spasms. The patient was unresponsive to conventional antiepileptic therapy, and genetic testing with whole exome and mitochondrial genome sequencing could not identify the underlying cause, so vigabatrin was initiated. The ophthalmic examination under anesthesia for vigabatrin toxicity screening revealed chorioretinal atrophy in the retinal periphery of both eyes, with two 3-disc diameter chorioretinal lacunae superotemporal and inferonasal to the optic nerve in the left eye. Given the neuroimaging findings of corpus callosum hypoplasia with polymicrogyria and ocular findings, the patient was diagnosed with Aicardi syndrome. Genetic testing revealed a novel duplication event at the Xp22 locus.

CONCLUSIONS

Aicardi syndrome, albeit a rare condition, should always be considered in the differential diagnosis when investigating a female child with refractory seizures in early childhood. Genetic testing may help further our understanding of AIS and the search for a genetic etiology.

Clinical characterization of epilepsy in children with chromosomal aberration 47, XXY

OBJECTIVE

The phenotype of the chromosomal aberration 47, XXY exhibits considerable heterogenicity. In addition, epilepsy is extremely uncommon in individuals with this chromosomal disorder. As a result, the clinical characteristics of epilepsy in these patients remain poorly understood.

METHODS

Clinical data and the evolution of epilepsy in a boy diagnosed with chromosomal aberration 47, XXY were collected and analyzed. Furthermore, a systematic literature review was conducted to examine the relationship between chromosomal aberration 47, XXY and epilepsy in children.

RESULTS

We identified a novel phenotype associated with the chromosomal anomaly 47, XXY in a 2-year-2-month-old boy who presented with self-limited epilepsy with autonomic seizures at onset, followed by developmental and/or epileptic encephalopathy with spike-wave activation in sleep (D/EE-SWAS), which was responsive to corticosteroid treatment. Including the present case, we analyzed 21 cases of children diagnosed with epilepsy due to the presence of the 47, XXY chromosomal anomaly. The most common types of epilepsy were focal combined generalized epilepsy (n = 9), epileptic spasms (n = 6), and generalized epilepsy (n = 4). There were six cases of infantile epileptic spasm syndrome (IESS) (n = 5) and developmental and epileptic encephalopathy (n = 1), one case of Lennox-Gastaut syndrome, and one case of D/EE-SWAS. Apart from corticosteroids in IESS, 15 antiseizure medications (ASMs) were prescribed to eight children in this cohort, with valproate (n = 5) being the most frequently used.

CONCLUSIONS

The epilepsy types and syndromes associated with the chromosomal anomaly 47, XXY demonstrated considerable heterogeneity. Among the observed phenotypes, IESS and focal epilepsy, which displayed partial responsiveness to multiple ASMs, were the most prevalent.

Genetic heterogeneity in corpus callosum agenesis

The corpus callosum is the largest white matter structure connecting the two cerebral hemispheres. Agenesis of the corpus callosum (ACC), complete or partial, is one of the most common cerebral malformations in humans with a reported incidence ranging between 1.8 per 10,000 livebirths to 230–600 per 10,000 in children and its presence is associated with neurodevelopmental disability. ACC may occur as an isolated anomaly or as a component of a complex disorder, caused by genetic changes, teratogenic exposures or vascular factors. Genetic causes are complex and include complete or partial chromosomal anomalies, autosomal dominant, autosomal recessive or X-linked monogenic disorders, which can be either de novo or inherited. The extreme genetic heterogeneity, illustrated by the large number of syndromes associated with ACC, highlight the underlying complexity of corpus callosum development. ACC is associated with a wide spectrum of clinical manifestations ranging from asymptomatic to neonatal death. The most common features are epilepsy, motor impairment and intellectual disability. The understanding of the genetic heterogeneity of ACC may be essential for the diagnosis, developing early intervention strategies, and informed family planning. This review summarizes our current understanding of the genetic heterogeneity in ACC and discusses latest discoveries.

Fetal Brain Development: Regulating Processes and Related Malformations

This paper describes the contemporary state of knowledge regarding processes that regulate normal development of the embryonic–fetal central nervous system (CNS). The processes are described according to the developmental timetable: dorsal induction, ventral induction, neurogenesis, neuronal migration, post-migration neuronal development, and cortical organization. We review the current literature on CNS malformations associated with these regulating processes. We specifically address neural tube defects, holoprosencephaly, malformations of cortical development (including microcephaly, megalencephaly, lissencephaly, cobblestone malformations, gray matter heterotopia, and polymicrogyria), disorders of the corpus callosum, and posterior fossa malformations. Fetal ventriculomegaly, which frequently accompanies these disorders, is also reviewed. Each malformation is described with reference to the etiology, genetic causes, prenatal sonographic imaging, associated anomalies, differential diagnosis, complimentary diagnostic studies, clinical interventions, neurodevelopmental outcome, and life quality.

A rare case of bilateral vitreoretinopathy of Aicardi syndrome

Purpose

To report a rare case of Aicardi syndrome presenting with concurrent peripheral retina nonperfusion with 360-degree neovascularization in the right eye and stalk tissue with a peripapillary fibrovascular membrane and tractional retinal detachment (TRD) in the left eye.

Observations

A one-month-old girl was referred for an ophthalmic evaluation to confirm the diagnosis of Aicardi syndrome due to abnormal brain magnetic resonance imaging. A 360-degree circumferential peripheral avascular retina with extensive neovascularization was present in the right eye. Stalk tissue with fibrovascular proliferation causing TRD was found in the left fundus. The retina of the right eye became quiescent after completing peripheral laser photocoagulation. The detached retina in the left eye was flattened, and the peripapillary chorioretinal lacunae became visible one year after surgical removal of the traction. In addition, the axial length growth of the left eye regained.

Conclusion and importance

This is a rare case of Aicardi syndrome with concurrent peripapillary fibrovascular traction in one eye and peripheral retina nonperfusion in the other eye. Surgical intervention is vital not only for removing the traction and flattening the retina but also for promoting continual growth of the eyeball.

Prenatal diagnosis of Aicardi syndrome based on a suggestive imaging pattern: A multicenter case-series

Objectives

To characterize a suggestive prenatal imaging pattern of Aicardi syndrome using ultrasound and MR imaging.

Methods

Based on a retrospective international series of Aicardi syndrome cases from tertiary centers encountered over a 20‐year period (2000–2020), we investigated the frequencies of the imaging features in order to characterize an imaging pattern highly suggestive of the diagnosis.

Results

Among 20 cases included, arachnoid cysts associated with a distortion of the interhemispheric fissure were constantly encountered associated with complete or partial agenesis of the corpus callosum (19/20, 95%). This triad in the presence of other CNS disorganization, such as polymicrogyria (16/17, 94%), heterotopias (15/17, 88%), ventriculomegaly (14/20, 70%), cerebral asymmetry [14/20, 70%]) and less frequently extra‐CNS anomaly (ocular anomalies [7/11, 64%], costal/vertebral segmentation defect [4/20, 20%]) represent a highly suggestive pattern of Aicardi syndrome in a female patient.

Conclusion

Despite absence of genetic test to confirm prenatal diagnosis of AS, this combination of CNS and extra‐CNS fetal findings allows delineation of a characteristic imaging pattern of AS, especially when facing dysgenesis of the corpus callosum.

What is already known about this topic?

Aicardi syndrome (AS) is a rare developmental encephalopathy, characterized by the classic triad of infantile spasms, agenesis of the corpus callosum, and chorioretinal lacunae

As the genetic etiology of AS is unknown and its classic triad cannot be extrapolated to prenatal diagnosis, to establish a prenatal imaging pattern is of major interest

What does this study add?

We confirmed and completed a prenatal imaging pattern highly suggestive of AS, based on the most frequent features encountered in a large series: arachnoid cysts associated with a distortion of the interhemispheric fissure, agenesis of the corpus callosum, cortical malformations and heterotopias, and less frequently extra‐CNS anomaly (ocular anomalies, costal/vertebral segmentation defect)

Aicardi syndrome in a 7-month-old girl with tonic seizures and skeletal defects: A case report

Introduction

and importance: Aicardi syndrome (AS) is a rare genetic syndrome characterized by a triad of features: agenesis or hypogenesis of corpus callosum, chorioretinal lacunae, and infantile spasms, along with other neurodevelopmental, ocular, craniofacial, gastrointestinal, and musculoskeletal disorders. The precise etiology of AS is unknown, and establishing a diagnosis is challenging since it is an extremely rare syndrome and may mimic other congenital neurological defects.

Case presentation

A 2-month-old girl was brought to our hospital, she developed multiple episodes of generalized spasticity with hyperflexion of upper and lower extremities on trunk (tonic seizure), with fast jerking movements of the eye, with signs of Psychomotor Development delay.

Clinical discussion

Ophthalmic examination showed bilateral medial strabismus without nystagmus, Retinal examination showed bilateral small peripapillary well-circumscribed chorioretinal lacunae with hyperpigmented borders, thoracic spine x-ray (AP view) showed hemivertebrae and loss of height in the 7th and 8th thoracic vertebral body. Magnetic Resonance Imaging (MRI) revealed grey matter heterotopia, underdevelopment of the left operculum, hypogenesis of the corpus callosum, hypogenesis of inferior vermis, and multiple cysts with peripheral enhancing. Eventually, the diagnosis of AS is confirmed by the results of radiological imaging and ophthalmology exam.

Conclusion

In this paper, we report a case of Aicardi syndrome diagnosed in a 7-month-old girl with frequent tonic seizures. We report this case to highlight that Aicardi syndrome should be considered in the differential diagnosis in cases of frequent tonic seizures with abnormal findings on retinal examination and characteristic findings on MRI.

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Aicardi syndrome (AS) is a rare syndrome characterized by a triad of features.

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AS triad is callosal hypogenesis, chorioretinal lacunae, and infantile spasms.

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Establishing the diagnosis of AS is challenging.

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AS may mimic other congenital neurological defects.

Basal Ganglia Dysmorphism in Patients With Aicardi Syndrome

OBJECTIVE

Aiming to detect associations between neuroradiologic and EEG evaluations and long-term clinical outcome in order to detect possible prognostic factors, a detailed clinical and neuroimaging characterization of 67 cases of Aicardi syndrome (AIC), collected through a multicenter collaboration, was performed.

METHODS

Only patients who satisfied Sutton diagnostic criteria were included. Clinical outcome was assessed using gross motor function, manual ability, and eating and drinking ability classification systems. Brain imaging studies and statistical analysis were reviewed.

RESULTS

Patients presented early-onset epilepsy, which evolved into drug-resistant seizures. AIC has a variable clinical course, leading to permanent disability in most cases; nevertheless, some cases presented residual motor abilities. Chorioretinal lacunae were present in 86.56% of our patients. Statistical analysis revealed correlations between MRI, EEG at onset, and clinical outcome. On brain imaging, 100% of the patients displayed corpus callosum malformations, 98% cortical dysplasia and nodular heterotopias, and 96.36% intracranial cysts (with similar rates of 2b and 2d). As well as demonstrating that posterior fossa abnormalities (found in 63.63% of cases) should also be considered a common feature in AIC, our study highlighted the presence (in 76.36%) of basal ganglia dysmorphisms (never previously reported).

CONCLUSION

The AIC neuroradiologic phenotype consists of a complex brain malformation whose presence should be considered central to the diagnosis. Basal ganglia dysmorphisms are frequently associated. Our work underlines the importance of MRI and EEG, both for correct diagnosis and as a factor for predicting long-term outcome.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for patients with AIC, specific MRI abnormalities and EEG at onset are associated with clinical outcomes.

Unsolved recognizable patterns of human malformation: Challenges and opportunities

Due to the efforts of the clinical and scientific communities and boosted by recent advances in genetic technologies, we now understand the molecular mechanisms underlying most of the frequent and recognizable human malformation syndromes. However, some well-established human malformation syndromes remain without a molecular diagnosis despite intensive investigation. This issue of Seminars mines the phenotypic entries in OMIM and estimates that of the documented 2,034 unsolved entries likely to represent a rare genetic disease, only 160 are well-established and possibly amenable to investigation. This issue also reviews well-characterized and extensively investigated human malformation syndromes and associations that remain unsolved, including the following: Dubowitz syndrome (MIM 223370%), Hallermann-Streiff syndrome (MIM 234100%), PHACE syndrome (MIM 606519), Oculocerebrocutaneous syndrome (MIM 164180), Aicardi syndrome (MIM 304050%), Gomez-Lopez-Hernandez syndrome and Rhombencephalosynapsis (MIM 601853%), VACTERL (MIM 192350%), and Nablus syndrome (MIM #608156). Possible explanations for their intractability to molecular diagnosis are explored, including genetic and phenotypic heterogeneity, mosaicism, epigenetics, gene-environment interactions, and other non-Mendelian contributions. Finally, this issue of Seminars presents a path forward for these unsolved rare conditions and suggests a renewed focus on solving amendable OMIM disorders. It is clear that the way forward will require new technologies, global cooperation, and data sharing; these will also be necessary to help reach the vision of the International Rare Diseases Research Consortium (IRDiRC), that is to enable all people living with a rare disease to receive an accurate diagnosis, care and available therapy within 1 year of coming to medical attention.