Microlissencephaly: A Heterogeneous Malformation of Cortical Development

Barkovich, A. James; Ferriero, Donna M.; Barr, Robert M.; Gressèns, Pierre; Dobyns, William B.; Truwit, Ch. L.; Evrard, P.

doi:10.1055/s-2007-973545

Cited by 94 publications

(62 citation statements)

References 4 publications

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“…This term, encompassed in a classification system of the lissencephalies published by Barkovich [1995], was proposed by Evrard et al [1982Evrard et al [ , 1989] to classify infants with severe micrencephaly who die within the first months of life, two traits not present in our study children. However, the microcephaly, simplified gyral pattern, and normal cortical thickness found in our affected subjects are compatible with criteria described in a new classification that encompasses the term microlissencephaly and that uses neonatal course and neuroradiological findings to determine clinical outcome in microcephalic patients [Barkovich et al, 1996[Barkovich et al, , 1998]. Microlissencephaly comprises a heterogenous group of disorders with a strong genetic component (usually autosomal recessive) that are thought to be caused by arrested gyral development at various times during the proliferative phase of cortical development.…”

Section: Discussionsupporting

confidence: 81%

Microcephaly with simplified gyral pattern in six related children

et al. 1999

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We describe clinical and neurophysiological findings in six related children with congenital microcephaly, seizures that began within the first 2-4 months of life, and severe mental retardation (MR). These affected children (five girls and one boy), born to two women who are half-sisters, inherited the disease as an autosomal recessive trait. Physical examination of these children did not show any of the anomalies in the known cortical malformation syndromes such as lissencephaly types I and II. Neuroradiological studies in these children documented microcephaly and a simplified gyral pattern with no pachygyria. Chromosomal analysis showed neither karyotypic abnormalities nor a microdeletion at 17p13.3, site of the lissencephaly type I gene locus (LIS1). Genetic studies failed to show linkage of this family to LIS1, LIS2 (a region on chromosome 2p homologous to LIS1), or MCPH1 (a locus for primary autosomal recessive microcephaly). The unique clinical and genetic findings in this family suggest that these children may be affected by an as-of-yet unmapped neuronal proliferation disorder.

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Section: Discussionsupporting

confidence: 81%

Microcephaly with simplified gyral pattern in six related children

et al. 1999

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“…Primary microcephaly and MSG might hence represent a phenotypic continuum. Five types of MSG have however been delineated on the basis of MRI and neurodevelopmental findings [Barkovich et al, 1998], and the clinical phenotype may be more severe than for MCPH. Mental retardation ranges from mild to moderate (MSG type 1) to severe (types 2-5), and pyramidal signs may be observed.…”

Section: Introductionmentioning

confidence: 99%

Primary microcephaly with ASPM mutation shows simplified cortical gyration with antero‐posterior gradient pre‐ and post‐natally

Désir

Cassart

David

et al. 2008

American J of Med Genetics Pt A

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Primary microcephaly is a disorder of brain development characterized by a congenitally small but normally formed brain, and non-progressive mild-to-moderate mental retardation. Most cases are inherited in an autosomal recessive pattern, with genetic heterogeneity, the ASPM locus being most common. Postnatal imaging data are scarce and prenatal imaging unreported. Microcephaly with simplified gyral pattern shares features with primary microcephaly, but it is not clear whether these disorders are part of a phenotypic continuum. We examined a consanguineous family with a daughter affected with primary microcephaly and an ongoing pregnancy. We performed prenatal and postnatal brain magnetic resonance imaging and genetic analyses in the course of genetic evaluation. The affected daughter and the fetus were homozygous for polymorphic markers linked to the ASPM locus, and we identified a novel, truncating ASPM mutation by direct sequencing of the gene. Imaging at 30 and 35 gestational weeks showed microcephaly with simplified gyration, more severe anteriorly. The antero-posterior gradient of gyration persisted 1 week after birth. Brain imaging in the affected sister also showed some degree of a predominantly anterior simplification of gyration. Our data suggest that one form of autosomal recessive microcephaly is allelic to at least a subset of microcephaly with simplified gyral pattern, and that the neuronal depletion associated with the ASPM defect predominantly affects the anterior cortex.

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“…2,3 Some academics have advocated for defining severe microcephaly as an HC more than 3 SDs below the mean. [4][5][6][7] Other than where specified, this parameter uses the usual definition of microcephaly. Recommended methods for HC measurement are described in appendix 2.…”

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confidence: 99%

Practice Parameter: Evaluation of the child with microcephaly (an evidence-based review) [RETIRED]

et al. 2009

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Objective: To make evidence-based recommendations concerning the evaluation of the child with microcephaly. Methods:Relevant literature was reviewed, abstracted, and classified. Recommendations were based on a 4-tiered scheme of evidence classification. Results:Microcephaly is an important neurologic sign but there is nonuniformity in its definition and evaluation. Microcephaly may result from any insult that disturbs early brain growth and can be seen in association with hundreds of genetic syndromes. Annually, approximately 25,000 infants in the United States will be diagnosed with microcephaly (head circumference ϽϪ2 SD). Few data are available to inform evidence-based recommendations regarding diagnostic testing. The yield of neuroimaging ranges from 43% to 80%. Genetic etiologies have been reported in 15.5% to 53.3%. The prevalence of metabolic disorders is unknown but is estimated to be 1%. Children with severe microcephaly (head circumference ϽϪ3 SD) are more likely (ϳ80%) to have imaging abnormalities and more severe developmental impairments than those with milder microcephaly (Ϫ2 to Ϫ3 SD; ϳ40%). Coexistent conditions include epilepsy (ϳ40%), cerebral palsy (ϳ20%), mental retardation (ϳ50%), and ophthalmologic disorders (ϳ20% to ϳ50%).Recommendations: Neuroimaging may be considered useful in identifying structural causes in the evaluation of the child with microcephaly (Level C). Targeted and specific genetic testing may be considered in the evaluation of the child with microcephaly who has clinical or imaging abnormalities that suggest a specific diagnosis or who shows no evidence of an acquired or environmental etiology (Level C). Screening for coexistent conditions such as cerebral palsy, epilepsy, and sensory deficits may also be considered (Level C). Further study is needed regarding the yield of diagnostic testing in children with microcephaly. Neurology Microcephaly is an important neurologic sign but there is nonuniformity in the definition of microcephaly and inconsistency in the evaluation of affected children.1,2 Microcephaly is usually defined as a head circumference (HC) more than 2 SDs below the mean for age and gender.2,3 Some academics have advocated for defining severe microcephaly as an HC more than 3 SDs below the mean.4-7 Other than where specified, this parameter uses the usual definition of microcephaly. Recommended methods for HC measurement are described in appendix 2.If HC is normally distributed, 2.3% of children should by definition be microcephalic. However, published estimates for HC ϽϪ2 SD at birth are far lower, at 0.56% 8 and 0.54%. 9 The difference may be accounted for by a non-normal distribution, postnatal development of microcephaly, or incomplete ascertainment. Severe microcephaly would be expected Appendices e-1 through e-6 and references e1-e12 are available on the Neurology Web site at www.neurology.org.

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Microlissencephaly: A Heterogeneous Malformation of Cortical Development

Cited by 94 publications

References 4 publications

Microcephaly with simplified gyral pattern in six related children

Microcephaly with simplified gyral pattern in six related children

Primary microcephaly with ASPM mutation shows simplified cortical gyration with antero‐posterior gradient pre‐ and post‐natally

Practice Parameter: Evaluation of the child with microcephaly (an evidence-based review) [RETIRED]

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