Fetal type II lissencephaly: a case report

Seizures and EEG characteristics in a cohort of pediatric patients with dystroglycanopathies

PURPOSE

To delineate the seizure type, phenotype and V-EEG patterns of dystroglycanopathy (DGP) and correlate them with the neuroradiological and genetic results.

METHODS

Patients with seizures were screened from our dystroglycanopathy database from January 2010 to March 2021. Detailed clinical information, including seizure type, brain magnetic resonance imaging (MRI), EEG and genetic analysis, was collected.

RESULTS

Thirteen patients (15.1%, 13/86) had seizures. Most patients had a severe phenotype. The mean age at first seizure onset was 2 years and 8 months. The most common seizure type was generalized tonic-clonic seizure (GTCS), with 92.3% (12/13) induced by fever. Three patients were diagnosed with epilepsy. Most patients did not take any medicine. A few patients had irregular use of antiseizure medications (ASMs). Of the 13 patients, seven patients were diagnosed with MEB, four patients with POMGNT1 mutations, two with ISPD mutations, and one with POMT1 mutation. Three patients were diagnosed with FCMD with FKTN mutations. Two patients were diagnosed with CMD-MR, one patient with ISPD mutation, and one with POMT1 mutation. One patient was diagnosed with LGMD with FKRP mutation. Nine patients underwent EEG examination, and eight patients had abnormal EEG results, including abnormal background activities in three patients, abnormal background activities combined with paroxysmal discharges in three patients, pure paroxysmal discharges in one patient and positive phase sharp waves in the occipital region in one patient. For radiology, brain MRI was available for 12 patients. The brain MRI of nine patients showed type II lissencephaly. Two patients showed cerebellar hypoplasia and brainstem hypoplasia. One patient had a normal brain MRI result. Patients with type II lissencephaly usually had abnormal background activities and paroxysmal discharges.

CONCLUSION

The seizure phenotype of dystroglycanopathy (DGP) is characterized by GTCS, which was the most common seizure type, while focal seizures and epileptic spasms could also occur in DGP patients. Most seizures were induced by fever. Seizures were relatively more frequent in severe phenotypes of DGP, such as FCMD and MEB. Abnormal background activities were the most common EEG patterns, which were closely related to type II lissencephaly.

Neuronal migration disorders

Neuronal migration disorders are a category of developmental brain disorders leading to cortical dysplasia. This group of disorders is characterized by defective movement of neurons from the place of origin along the lining of the lateral ventricle, to the eventual place of residence in the correct laminar position within the cerebral cortex. As a result of defective migration, affected individuals typically display mental retardation and epilepsy. Although patients with the more severe forms of these disorders often present during infancy, patients may present at any age from newborn to adulthood. The migration defect may be generalized or focal, and may be disturbed at any of several stages, leading to several distinct radiographical and clinical presentations. The human phenotypes suggests that there are at least four distinct and clinically-important steps in cortical neuronal migration, and the identification of the responsible genes suggests that multiple cellular processes are critical for correct neuronal positioning.

Neuronal migration, cerebral cortical development, and cerebral cortical anomalies

Cerebral cortical malformations are relatively common anomalies identified by neuroimaging and pathologically in patients with epilepsy and mental retardation. A disruption in neuronal migration during central nervous system development has been postulated as the pathogenesis for many of these disorders. Recently, the cell migration hypothesis has been proven accurate for lissencephaly, subcortical band heterotopia, and periventricular nodular heterotopia. Furthermore, advances in cellular and molecular biology have begun elucidating the fundamental mechanisms underlying these migration disorders. These data have resulted in redefining and recategorizing specific malformations based on their molecular genetic abnormality. In this review we shall discuss the current understanding of neuronal migration in the developing cerebral cortex, the evaluation of these patients, and attempt to describe the pathogenesis for several well-characterized human disorders of cell migration.

The role of Glial-Pial barrier lesions and impaired vascularization in anomalous formation of cortical convolutions

The abnormal patterns of cerebral convolutions range from severe to small anomalies restricted to tertiary gyri and sulci. Lesions within Glial-Pial barrier were found in examined cases with cortical developmental abnormalities. Anomalies and impaired function of vessels penetrating the cortex from meningeal plexus coexisted often with Glial-Pial barrier lesions. We are able to say that our cases constitute a group of graded changes demonstrating that both observed developmental lesions vascular and/or Glial-Pial barrier damage may result in cortical anomalies. Their formation and character depend on the stage of cortical maturation when analyzed lesions occur.

Cell migration and cerebral cortical development

This annotation describes the clinical and pathological features of several conditions believed to result from a primary defect in cell migration which include the lissencephalies, pachygria, polymicrogyrias, and focal cortical dysplasia. A variety of factors must be considered in pathogeneses, including cellular proliferation, cell death, post-migrational intracortical growth and development, axonogenesis and dendritogenesis. At least two distinct types of lissencephaly exist. Classic (also known as Type I) lissencephaly is the prototypic pattern being seen in autosomal dominant Miller-Dieker syndrome, in addition to autosomal recessive and X-linked forms. The Miller-Dieker syndrome locus (LIS-1) encodes the platelet activating factor acetylhydrolase-1, beta1 subunit. The gene for an X-linked form of lissencephaly (XLIS) encodes a protein called doublecortin. Cobblestone (type II) lissencephaly is most commonly seen in patients with the Walker-Warburg syndrome, and also occurs in a group of disorders associated with congenital muscular dystrophy, including Finnish 'muscle-eye-brain' disease and Fukuyama muscular dystrophy. Controversy exits as to whether polymicrogyria is a malformation or a disruption of development. The answer is likely both. Polymicrogyria is believed to arise from defects occurring between 17 and 25 or 26 weeks gestation. Heterotopia can be sporadic, inherited as a simple Mendelian trait, or may be part of a more complex syndrome being characterized by collections of disorganized grey matter in inappropriate places. X-linked periventricular heterotopia syndrome is caused by mutations in filamin-1. In addition to those described above, many other syndromes show lissencephaly, pachygyria and polymicrogyria and many cases are not easily classified into any particular syndrome.

Neuronal migration defects of the cerebral cortex: a destination debacle

Disruptions in neuronal migration have been postulated as the basis for many cerebral malformations including lissencephaly, cortical heterotopia, and double cortex. Recently, the genetic basis for some of these disorders has been identified. In this review, we highlight recent advances in our understanding of the molecular mechanisms of neuronal migration and its relationship to cerebral cortical development and neuronal migration disorders. This has allowed us to begin categorizing specific malformations based on their molecular etiology.

Congenital muscular dystrophies: 1997 update

The congenital muscular dystrophies (CMDs) comprise a heterogeneous group of muscle disorders with onset in utero or during the first year of life. Several forms of CMD show various types of brain involvement in addition to a muscular dystrophy. Two forms are defined at the molecular level: merosin deficient-CMD caused by mutations in the LAMA2-gene on chromosome 6q2. Fukuyama congenital muscular dystrophy (FCMD) is prevalent in Japan and caused by an as yet unidentified gene on chromosome 9q31. At least two further forms of CMD with brain involvement are nosologically well defined: Walker--Warburg-CMD is characterized by lissencephaly type 11, eye dysgenesis and muscular dystrophy. This autosomal recessive disorder is fatal or results in complete lack of development. A similar but much milder phenotype with pachygyria of the brain, various degrees of eye changes and milder muscular dystrophy that is compatible with achievement of simple motor milestones has been described under the name of muscle-eye-brain disease (MEB) in Finland. A number of nosologically less distinct forms of muscular dystrophy have been outlined such as 'pure' CMD without brain involvement, CMD with cerebellar hypoplasia or CMD type Ullrich with hyperelasticity of the distal joints. Several other CMD phenotypes are known, some of which are suggestive of more distinctly separate nosological entities due to their occurrence in siblings or due to a characteristic pattern of clinical, histopathological and imaging features, and await further clarification.

Widespread neuronal ectopia associated with secondary defects in cerebrocortical chondroitin sulfate proteoglycans and basal lamina in MARCKS-deficient mice

Mice deficient in MARCKS, a prominent neural substrate for protein kinase C (PKC), die before or shortly after birth. They exhibit high frequencies of exencephaly, universal agenesis of forebrain commissures, and abnormalities of cerebral cortical and retinal lamination. We show here that these mice have wide-spread and severe neuronal ectopia in the outer layers of the developing forebrain, manifested by the migration of clusters of developing neuroblasts through the basal lamina and often through the pial membrane and into the subarachnoid space. This abnormality became apparent by Embryonic Day (E) 13 or 14, shortly after the formation of the early marginal zone. MARCKS deficiency was associated with decreased staining for marginal zone chondroitin sulfate proteoglycans; this decrease was detectable earlier in development than the neuronal ectopia. Later in development, there was also marked disruption of the basal lamina at the pial-glial interface, as evidenced by gross abnormalities in laminin and reticulin staining; however, the basal lamina appeared normal at E9.5. These data indicate that MARCKS is required for the prevention of neuronal ectopia during development. Potential mechanisms responsible for the neuronal ectopia in the MARCKS-deficient mice include decreased expression or increased proteolytic destruction of basal lamina proteins and marginal zone chondroitin sulfate proteoglycans in the developing brain.

Fetal type II lissencephaly: a case report

Type II lissencephaly is a rare cortical malformation associated with a number of clinical syndromes, including Walker-Warburg syndrome and some forms of congenital muscular dystrophy. The neuropathology of a 20-week fetus is described showing the pathogenesis of the malformation, which appears to result from abnormal migration of neurons through the pial-glial barrier into the leptomeninges.

Development of the cortical dysplasia of type II lissencephaly

A detailed neuropathological study of five immature brains with type II lissencephaly is reported. The cases described include two pairs of siblings. One infant survived for 2 months after birth, the others died at 18, 20, 20 and 32 weeks of gestation. This series of cases demonstrates the sequence in which the malformation develops from mid-gestation to post-natal life and shows that type II lissencephaly is not an intracortical malformation but is the result of massive glial and neuronal ectopia in the leptomeninges. This results from a failure of arrest of neuronal migration due to defects in the integrity of the pial/glial barrier.