Aicardi syndrome

Early-onset ataxia with ocular motor apraxia and hypoalbuminemia/ataxia with oculomotor apraxia 1

DNA single-strand breaks (SSBs) are non-overlapping discontinuities in strands ofa DNA duplex. Significant attention has been given on the DNA SSB repair (SSBR) system in neurons, because the impairment of the SSBR causes human neurodegenerative disorders, including early-onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH), also known as ataxia-oculomotor apraxia Type 1 (AOA1). EAOH/AOA1 is characterized by early-onset slowly progressive ataxia, ocular motor apraxia, peripheral neuropathy and hypoalbuminemia. Neuropathological examination reveals severe loss of Purkinje cells and moderate neuronal loss in the anterior horn and dorsal root ganglia. EAOH/AOA1 is caused by the mutation in the APTX gene encoding the aprataxin (APTX) protein. APTX interacts with X-ray repair cross-complementing group 1 protein, which is a scaffold protein in SSBR. In addition, APTX-defective cells show increased sensitivity to genotoxic agents, which result in SSBs. These results indicate an important role ofAPTX in SSBR. SSBs are usually accompanied by modified or damaged 5'- and 3'-ends at the break site. Because these modified or damaged ends are not suitable for DNA ligation, they need to be restored to conventional ends prior to subsequent repair processes. APTX restores the 5'-adenylate monophosphate, 3'-phosphates and 3'-phosphoglycolate ends. The loss of function of APTX results in the accumulation of SSBs, consequently leading to neuronal cell dysfunction and death.

A developmental and genetic classification for midbrain-hindbrain malformations

Advances in neuroimaging, developmental biology and molecular genetics have increased the understanding of developmental disorders affecting the midbrain and hindbrain, both as isolated anomalies and as part of larger malformation syndromes. However, the understanding of these malformations and their relationships with other malformations, within the central nervous system and in the rest of the body, remains limited. A new classification system is proposed, based wherever possible, upon embryology and genetics. Proposed categories include: (i) malformations secondary to early anteroposterior and dorsoventral patterning defects, or to misspecification of mid-hindbrain germinal zones; (ii) malformations associated with later generalized developmental disorders that significantly affect the brainstem and cerebellum (and have a pathogenesis that is at least partly understood); (iii) localized brain malformations that significantly affect the brain stem and cerebellum (pathogenesis partly or largely understood, includes local proliferation, cell specification, migration and axonal guidance); and (iv) combined hypoplasia and atrophy of putative prenatal onset degenerative disorders. Pertinent embryology is discussed and the classification is justified. This classification will prove useful for both physicians who diagnose and treat patients with these disorders and for clinical scientists who wish to understand better the perturbations of developmental processes that produce them. Importantly, both the classification and its framework remain flexible enough to be easily modified when new embryologic processes are described or new malformations discovered.

A genome-wide screen for copy number alterations in Aicardi syndrome

Aicardi syndrome is a severe neurodevelopmental disorder that affects females or rarely males with a 47,XXY karyotype. Therefore, it is thought to be caused by heterozygous defects in an essential X-linked gene or by defects in an autosomal gene with sex-limited expression. Because all reported cases are sporadic with one exception, traditional linkage analysis to identify the mutant gene is not possible, and the de novo mutation rate must be high. As an alternative approach to localize the mutant gene, we screened the DNA of 38 girls with Aicardi syndrome by high-resolution, genome-wide array comparative genomic hybridization for copy number gains and losses. We found 110 copy number variants (CNVs), 97 of which are known, presumably polymorphic, CNVs; 8 have been seen before in unrelated studies in unaffected individuals. Four previously unseen CNVs on autosomes were each inherited from a healthy parent. One subject with Aicardi syndrome had a de novo loss of X-linked copy number in a region without known genes. Detailed analysis of this and flanking regions did not reveal CNVs or mutations in annotated genes in other affected subjects. We conclude that, in this study population of 38 subjects, Aicardi syndrome is not caused by CNVs detectable with the high-resolution array platform that was used.

Aicardi syndrome mimicking intrauterine hydrocephalus

Congenital enlargement of the cerebral ventricles is now commonly recognized in utero due to the availability of high resolution prenatal ultrasonography. It is important to distinguish between congenital hydrocephalus and ventricular enlargement due to malformations, infections or other destructive processes because these disorders can have markedly different prognoses. We report an infant diagnosed with Aicardi syndrome in the newborn period based on brain MRI and ophthalmological findings after she was referred for evaluation of hydrocephalus seen on fetal ultrasound. Aicardi syndrome most commonly comes to medical attention because of seizures later in infancy.

Aicardi syndrome: the importance of an ophthalmologist in its diagnosis

Aicardi syndrome is a rare genetic disorder. The salient features of this syndrome include agenesis of corpus callosum, chorioretinal lacunae and infantile spasms. Of these three, chorioretinal lacunae is the most constant feature present. This case highlights the importance of fundus findings by an ophthalmologist in making the diagnosis of this rare syndrome.

Prenatal diagnosed cyst of the quadrigeminal cistern in Aicardi syndrome

Aicardi syndrome is an X-linked dominant disorder characterized by the pathognonomic association of three clinical signs: agenesis of the corpus callosum, infantile spasms, and chorioretinal lacunae. This is a severe syndrome with an estimated survival rate of 76% at 6 years and 40% at 14 years and a maximum developmental level like a 12-month-old baby in 91% of cases. We illustrate a case of Aicardi syndrome with bilateral, small chorioretinal lacunae, infantile spasms with a typical hypsarrhythmia, defects of thoracic vertebra and bilateral absence of the 12th rib associated with an arachnoid cyst of the quadrigeminal cistern, and presence of the corpus callosum with a favorable outcome.

Aicardi syndrome in a 47, XXY male neonate with lissencephaly and holoprosencephaly

Aicardi syndrome (AS) is a rare neuro-ophthalmic disorder first described by Jean Aicardi in 1965 with a characteristic triad of corpus callosal agenesis (CCA), chorioretinal lacunae (CRL), and infantile spasms (IS). All known cases of AS have been sporadic and a responsible gene has not been identified. With 5 exceptional males, potential X-linked dominant genetic mutation characterizes AS occurring almost exclusively in girls. Most of male AS cases were still debatable in diagnosis either for their 46 XY karyotype or too atypical presentations to fit the formerly stricter diagnostic criteria. We report a 47, XXY male neonate presenting some undisputable, but otherwise some regarded as atypical features in AS. We compare his distinctively clinical pictures with previously reported male cases and find CRL is less pathognomonic and lissencephaly appears frequently among male AS. Because of insufficient genetic and biochemical markers for definite diagnosis at this moment, we suggest the experience of a relatively rare male case would help to shed light on the underlying genetic pathogenesis of AS.

Non-random X chromosome inactivation in Aicardi syndrome

Most females have random X-chromosome inactivation (XCI), defined as an equal likelihood for inactivation of the maternally- or paternally-derived X chromosome in each cell. Several X-linked disorders have been associated with a higher prevalence of non-random XCI patterns, but previous studies on XCI patterns in Aicardi syndrome were limited by small numbers and older methodologies, and have yielded conflicting results. We studied XCI patterns in DNA extracted from peripheral blood leukocytes of 35 girls with typical Aicardi syndrome (AIC) from 0.25 to 16.42 years of age, using the human androgen receptor assay. Data on 33 informative samples showed non-random XCI in 11 (33%), defined as a >80:20% skewed ratio of one versus the other X chromosome being active. In six (18%) of these, there was a >95:5% extremely skewed ratio of one versus the other X chromosome being active. XCI patterns on maternal samples were not excessively skewed. The prevalence of non-random XCI in Aicardi syndrome is significantly different from that in the general population (p < 0.0001) and provides additional support for the hypothesis that Aicardi syndrome is an X-linked disorder. We also investigated the correlation between X-inactivation patterns and clinical severity and found that non-random XCI is associated with a high neurological composite severity score. Conversely, a statistically significant association was found between random XCI and the skeletal composite score. Correlations between X-inactivation patterns and individual features were made and we found a significant association between vertebral anomalies and random XCI.

A male phenotype with Aicardi syndrome

Aicardi syndrome is a rare neurodevelopmental condition that occurs almost exclusively in women. We report a second male phenotype and 47,XXY karyotype with a typical presentation of the Aicardi syndrome including a midline arachnoid cyst.

Cerebellar migration defects in aicardi syndrome: an extension of the neuropathological spectrum

The Aicardi syndrome is characterized by infantile spasms, corpus callosum agenesis, and chorioretinal lacunae and almost exclusively affects females (very rarely, 47, XXY males). The crucial genetic mishap likely occurs in the postzygotic stage, but the variable clinical phenotype among the approximately 450 known cases has not been explained. No consistent mutations or deletions exist among patients. We encountered a baby girl with early onset infantile spasms. She had left-sided cleft lip/palate, costovertebral defects, scoliosis, callosal agenesis, and microphthalmia. She expired at the age of 3 months of respiratory infection. On autopsy she had thoracic hemivertebrae with rib defects, bilateral microphthalmia, microcornea, posterior colobomata, abnormalities of the retinal pigment epithelium, absence of normal ganglion cells in the retina, gross asymmetry of the brain with cerebral polymicrogyria, total callosal agenesis, cerebral subcortical and subependymal nodular heterotopias, cerebellar nodular heterotopias, and tegmental/basal unilateral brainstem hypoplasia. Cerebellar and retinal migration defects have not been described before in Aicardi syndrome and may have had a bearing on this patient's eventual outcome.

Aicardi syndrome in a genotypic male

Aicardi syndrome was originally described as a triad of partial or complete agenesis of the corpus callosum, infantile spasms, and pathognomic chorioretinal lacunae. Of approximately 200 cases reported since it was originally described in 1965, there have been no undisputed reports of Aicardi syndrome in a 46 XY male. Thus a dominant X-linked inheritance, presumed lethal in males, has been proposed. Herein we report a 5 year-old 46 XY male with the classic clinical triad of Aicardi syndrome.

Neuroimaging aspects of Aicardi syndrome

Aicardi syndrome is a rare neurodevelopmental disorder characterized by congenital chorioretinal lacunae, corpus callosum dysgenesis, seizures, polymicrogyria, cerebral heterotopias, intracranial cysts, and costovertebral defects. Cerebellar abnormalities have been described occasionally. Aicardi syndrome is sporadic and has been observed only in females and 47,XXY males. Therefore, it is thought to result from a mutation in an X-linked gene. Improved definition of the clinical phenotype should focus the selection of functional candidate genes for mutation analysis. Because central nervous system abnormalities are the most prominent component of the phenotype, we performed a detailed characterization of abnormalities identified on magnetic resonance neuroimaging studies from 23 girls with Aicardi syndrome, the largest cohort to undergo such review by a single group of investigators. All patients had polymicrogyria that was predominantly frontal and perisylvian and often associated with underopercularization. Periventricular nodular heterotopias, present in all patients, were more frequent than previously reported; 10 had single and 11 had multiple intracranial cysts. Posterior fossa abnormalities were also more frequent than previously described. Cerebellar abnormalities were noted in 95% of studies where they could be evaluated. As a novel finding, we noted tectal enlargement in 10 patients. Since mildly affected girls with variable callosal dysgenesis have now been reported, the constellation of frontal-dominant and perisylvian polymicrogyria, periventricular nodular heterotopias, intracranial cysts, and posterior fossa abnormalities, including tectal enlargement, should prompt consideration of the diagnosis of Aicardi syndrome. We further propose that improved characterization of the neurological phenotype will benefit the selection of candidate genes for mutation analysis.

New incidence, prevalence, and survival of Aicardi syndrome from 408 cases

We sought to determine the incidence, prevalence, and life expectancy of Aicardi syndrome from 408 cases compiled from multiple international sources. Last known age ranged from less than 1 month to 42 years. The incidence rates per live births for the United States and The Netherlands were 1 per 105 000 and 1 per 93 000, respectively. The prevalence in the United States is greater than 853 cases, and the worldwide estimate is several thousand. Forty-five cases were deceased (age range, 1 month to 33 years), and the risk of death peaked at age 16. The probability of survival at 27 years of age was 0.62 (95% CI, 0.47-0.77). The risk of death by age follows other congenital neurological disorders with a wide range in severity of functional disability. The longer life expectancy found in our study hints at a higher functioning capacity in Aicardi syndrome and may inform counseling to families.

Facial and physical features of Aicardi syndrome: infants to teenagers

Aicardi syndrome is a sporadic disorder that affects primarily females and is hypothesized to be caused by heterozygous mutations in an X-linked gene. Its main features include of a triad of infantile spasms, agenesis of the corpus callosum, and distinctive chorioretinal lacunae. Additional common findings include moderate to profound mental retardation, gray matter heterotopia, gyral anomalies, and vertebral and rib defects. To date, no consistent facial dysmorphisms have been described. We examined 40 girls with Aicardi syndrome and determined that consistent facial features appeared in over half the study participants and included a prominent premaxilla, upturned nasal tip, decreased angle of the nasal bridge, and sparse lateral eyebrows. Externally apparent microphthalmia was seen in 10/40 (25%). Various skin lesions (including multiple nevi, skin tags, hemangiomas, one giant melanotic nevus, and a history of a previously removed angiosarcoma) were present in 8/40 (20%). Hand abnormalities were seen in 3/40 (7.5%) and included camptodactyly, proximal placement of the thumb and hypoplasia of the fifth finger. This study clearly delineates the existence of a distinctive facial phenotype of Aicardi syndrome not previously described. We recommend that features of a prominent premaxilla with upturned nasal tip and vascular malformations/vascular tumors be added to the modified diagnostic criteria in order to improve the ability of geneticists to diagnose Aicardi syndrome.

Agenesis of the corpus callosum, optic coloboma, intractable seizures, craniofacial and skeletal dysmorphisms: an autosomal recessive disorder similar to Temtamy syndrome

Agenesis of the corpus callosum (ACC) is a common brain anomaly with a birth incidence of at least 1 in 4,000. ACC can occur as an isolated malformation or as a component of a syndrome. Here, we report on an autosomal recessive syndrome with ACC, optic coloboma, craniofacial dysmorphism, skeletal anomalies, and intractable seizures in a brother and sister from a consanguineous family. Homozygosity mapping excluded three genes, VAX1, ASXL2, and ZNF462, which have previously been implicated in ACC with optic coloboma. This case presents many features similar to Temtamy syndrome and will help in establishing the spectrum of this disorder.

Aicardi syndrome with favorable outcome: case report and review

Aicardi syndrome is a congenital disorder characterized by severe psychomotor retardation, corpus callosum agenesis, chorioretinal lacunae, and early-onset infantile spasms. The prognosis is generally poor for children with the classical form. We report a peculiar case of Aicardi syndrome characterized by corpus callosum hypoplasia, brain malformations with subependymal heterotopias, extensive chorioretinal lacunae, seizures, and normal cognitive functions. Therefore, the clinical picture of the syndrome is broader than originally described. Cognitive disorders should not be considered inevitable and the prognosis not ineludibly poor.

Screening of subtle copy number changes in Aicardi syndrome patients with a high resolution X chromosome array-CGH

Aicardi syndrome (AIC) is an uncommon neurodevelopmental disorder affecting almost exclusively females. Chief features include infantile spasms, corpus callosal agenesis, and chorioretinal abnormalities. AIC is a sporadic disorder and hypothesized to be caused by heterozygous mutations in an X-linked gene but up to now without any defined candidate region on the X chromosome. Array based comparative genomic hybridisation (array-CGH) has become the method of choice for the detection of microdeletions and microduplications at high resolution. In this study, for the first time, 18 AIC patients were analyzed with a full coverage X chromosomal BAC arrays at a theoretical resolution of 82 kb. Copy number changes were validated by real-time quantitation (qPCR). No disease associated aberrations were identified. For such conditions as AIC, in which there are no familial cases, additional patients should be studied in order to identify rare cases with submicroscopic abnormalities, and to pursue a positional candidate gene approach.

Aicardi syndrome associated with anterior cephalocele in a female infant

Aicardi syndrome is a triad of abnormalities that includes total or partial agenesis of the corpus callosum, chorioretinal lacunae, and infantile spasms. This syndrome was first described in 1965. A female infant with Aicardi syndrome associated with a nasoethmoidal cephalocele is described in this report. She presented with a history of unilateral nasal discharge since birth and seizures since age 1 week. She was microcephalic and there was visual impairment. A fleshy mass of the left nostril was noted. Ophthalmological evaluation revealed left exotropia, dysplastic optic discs and retina, 'morning glory' appearance of the left optic disc, and bilateral chorioretinal lacunae. Magnetic resonance imaging of the brain showed absence of the corpus callosum, dysmorphic changes of the lateral ventricles, a superiorly located third ventricle, heterotopic grey matter of the frontal lobes, a left nasoethmoidal cephalocele, and closed lip schizencephaly of the left frontal lobe. This female infant developed asymmetric infantile spasms at age 8 weeks. Surgical correction of the cephalocele was declined. She developed recurrent pneumonias secondary to aspiration of feeds and died at age 8 months during one of these events.

Intractable reflex audiogenic seizures in Aicardi syndrome

Aicardi syndrome (AS) is a rare disorder which includes the triad of total or partial agenesis of the corpus callosum, infantile spasms, and chorioretinal anomalies. Seizures and electroencephalogram findings observed in AS are polymorphic with both focal and generalized seizures. We first report on a patient affected by AS who presented with reflex audiogenic seizures specifically triggered by the starting tune of a popular television news. No other type of stimuli, either simple or complex, were able to precipitate the seizures in the patient. The severe cortical-subcortical lesions commonly observed in AS are associated with hyperexcitability of the cortices and may well account for the broad electroclinical patterns noted in this group of patients. From our report, the context of these patterns should be extended to include reflex audiogenic seizures.

Choroid plexus papilloma expansion over 7 years in Aicardi syndrome

Choroid plexus papillomas have been reported in Aicardi syndrome. Management of these tumors is controversial because their natural progression in Aicardi syndrome has only been rarely documented. This report describes the progression of such a tumor over 7 years in a girl with Aicardi syndrome. A magnetic resonance imaging study at 2 months of age demonstrated a right ventricular mass that was consistent with a unilateral choroid plexus papilloma. The mass enlarged over the next 7 years without causing any clinically apparent symptoms, ventricular enlargement, hydrocephalus, or mass effect. The tumor was removed without change in behavior or development. The known cases of Aicardi syndrome associated with choroid plexus papillomas are reviewed. The heterogeneous nature of this lesion is highlighted.

Phenotype and management of Aicardi syndrome: new findings from a survey of 69 children

Aicardi syndrome is a rare neurodevelopmental disorder characterized by agenesis of the corpus callosum, other developmental brain abnormalities, chorioretinal lacunae, and severe seizures. Current clinical knowledge is derived from small series that focus on these major defects. The authors performed a health survey on a large number of affected children to expand this knowledge and to uncover previously unrecognized features of Aicardi syndrome. Responses received from caregivers of 69 children with Aicardi syndrome met inclusion criteria for data analysis. Ages ranged from 5 months to 32 years (mean, 88 months). All subjects were girls, except for 1 boy with a 47,XXY karyotype. The authors found that the growth rate in Aicardi syndrome slows at age 10 years to below the 5th percentile and that weight gain slows at age 7 years to below the 25th percentile. The median age of survival was estimated at 18.5 (+/-4) years, more favorable than previously reported. The most common complication aside from seizures was gastrointestinal dysfunction, present in >90%. The results from this survey contribute new information on Aicardi syndrome that will benefit clinical management, and collected data will benefit phenotype-driven research toward its underlying cause.

Aicardi syndrome: an unusual case associated with pineal gland cyst and ventricular septal defect

Aicardi syndrome is a cerebroretinal disorder consisting of a heterogeneous spectrum of clinical findings that includes the triad of infantile spasms, agenesis of the corpus callosum, and chorioretinal lacunae. This report describes a 6-month-old girl who has all of the essential features suggestive of Aicardi syndrome, as well as a pineal gland cyst and ventricular septal defect. Although the characteristic features of Aicardi syndrome have been described, its association with pineal gland cyst and ventricular septal defect has not been reported in the literature.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.

Periventricular nodular heterotopia with overlying polymicrogyria

Polymicrogyria (PMG) and periventricular nodular heterotopia (PNH) are two developmental brain malformations that have been described independently in multiple syndromes. Clinically, they present with epilepsy and developmental handicaps in both children and adults. Here we describe their occurrence together as the two major findings in a group of at least three cortical malformation syndromes. We identified 30 patients as having both PNH and PMG on brain imaging, reviewed clinical data and brain imaging studies (or neuropathology summary) for all, and performed mutation analysis of FLNA in nine patients. The group was divided into three subtypes based on brain imaging findings. The frontal-perisylvian PNH-PMG subtype included eight patients (seven males and one female) between 2 days and 10 years of age. It was characterized by PNH lining the lateral body and frontal horns of the lateral ventricles and by PMG most severe in the posterior frontal and perisylvian areas, occasionally with extension to the parietal lobes beyond the immediate perisylvian cortex. The posterior PNH-PMG subtype consisted of 20 patients (15 male and 5 female) between 5 days and 40 years of age. It was characterized by PNH in the trigones, temporal and posterior horns of the lateral ventricles, and PMG most severe in the temporo-parieto-occipital regions. The third type was found in 2 females aged 7 months and 2 years, and was characterized by severe congenital microcephaly and more diffuse cortical abnormality. The PNH-PMG subtypes described here have distinct imaging and clinical phenotypes that suggest multiple genetic aetiologies involving defects in multiple genes, and a shared pathophysiological mechanism for PNH and PMG. The frontal-perisylvian and posterior subtypes both had skewing of the sex ratio towards males, which suggests the possibility of X-linked inheritance. Delineation of these syndromes will also aid in providing more accurate diagnosis and prognostic information for patients with these malformations.

Genetics of choroid plexus tumors

Choroid plexus tumors consist of papillomas and carcinomas. A variety of germline and somatic genetic changes have been demonstrated for each of these subtypes. In this paper, the authors summarize the current knowledge of the genetic bases of these tumors.