Lethal familial fetal akinesia sequence (FAS) with distinct neuropathological pattern: type III lissencephaly syndrome

Prenatal sonographic diagnosis of Dandy-Walker malformation and type III lissencephaly: A novel association

Dandy-Walker malformation (DWM) may occur as part of Mendelian disorders such as Walker-Warburg and Meckel-Gruber syndromes. We report a novel association with type III lissencephaly in a 22-week male fetus. Ultrasound showed fetal akinesia deformation sequence, single umbilical artery, microlissencephaly, hydranencephaly with cerebral lamination, DWM, and pontocerebellar hypoplasia. These abnormalities were confirmed by magnetic resonance imaging and autopsy, which also revealed pulmonary and adrenal hypoplasia, common mesentery and bilateral uretero-pyelo-calyceal dilatation. Neuropathological examination showed brain calcifications and diffuse neuronal degeneration. We conclude that DWM may be a feature of type III lissencephaly and that this association can be easily diagnosed by ultrasound.

Role of cytoskeletal abnormalities in the neuropathology and pathophysiology of type I lissencephaly

Type I lissencephaly or agyria-pachygyria is a rare developmental disorder which results from a defect of neuronal migration. It is characterized by the absence of gyri and a thickening of the cerebral cortex and can be associated with other brain and visceral anomalies. Since the discovery of the first genetic cause (deletion of chromosome 17p13.3), six additional genes have been found to be responsible for agyria–pachygyria. In this review, we summarize the current knowledge concerning these genetic disorders including clinical, neuropathological and molecular results. Genetic alterations of LIS1, DCX, ARX, TUBA1A, VLDLR, RELN and more recently WDR62 genes cause migrational abnormalities along with more complex and subtle anomalies affecting cell proliferation and differentiation, i.e., neurite outgrowth, axonal pathfinding, axonal transport, connectivity and even myelination. The number and heterogeneity of clinical, neuropathological and radiological defects suggest that type I lissencephaly now includes several forms of cerebral malformations. In vitro experiments and mutant animal studies, along with neuropathological abnormalities in humans are of invaluable interest for the understanding of pathophysiological mechanisms, highlighting the central role of cytoskeletal dynamics required for a proper achievement of cell proliferation, neuronal migration and differentiation.

Fetal akinesia deformation sequence with delayed skeletal muscle maturation and polymicrogyria: evidence for a hypoxic/ischemic pathogenesis

Multiple congenital contractures, also known as fetal akinesia deformation sequence (FADS) and related terms, result from decreased fetal movement. The underlying etiologies are diverse and include central nervous system (CNS) dysgeneses and primary myopathies. Persistent central nuclei or the presence of myotubes is often regarded as evidence of a primary myopathic etiology; however, these findings are also associated with impaired fetal innervation. We report 7 fetuses, estimated gestational age 20 to 23 weeks, with persistent myotubular morphology, a change that could be (mis)interpreted as a primary myopathy. In 4 of the patients, CNS histology showed hypoxic/ischemic injury, polymicrogyria, mineralized neurons, and microinfarcts with or without loss of anterior horn neurons. FADS cases with polymicrogyria have frequently been interpreted as a consequence of a primary brain malformation. Only a few descriptions of FADS associate polymicrogyria with CNS hypoxic/ischemic injury, however, and do not describe skeletal muscle maturation delay. We hypothesize that this combination of neural and muscular pathology is an under-recognized pattern in FADS, which results from diffuse hypoxic/ischemic injury involving the brain and spinal cord during early to middle gestation.

Pena-Shokeir phenotype (fetal akinesia deformation sequence) revisited

BACKGROUND

Pena and Shokeir described the phenotype of two sisters in 1974, and subsequently their features have become recognized as a sequence of deformational changes related to decreased or absent fetal movement (fetal akinesia deformation sequence [FADS]), because of the work of Moessinger (1983).

METHODS

Identification of reported cases by searching Online Mendelian Inheritance in Man, Medlines, the London Dysmorphology Database, and the references found in these articles. These case reports were reviewed, tabulated, and summarized.

RESULTS

It is now possible to recognize at least 20 familial types of Pena-Shokeir phenotype (PSP), based on the differences found in the reports of the natural history and pathology found at fetal and newborn autopsy. In addition, characteristic changes in the central nervous system seen with embryonic/fetal vascular compromise have been recognized in many reported cases. Most of the reported cases of PSP/FADS related to vascular compromise are sporadic, but familial cases have also been reported.

CONCLUSION

Lack of fetal movement (fetal akinesia) in humans produces a recognizable sequence of deformations. Many developmental processes must be accomplished for fetal movement to be normal, and for extra-uterine life to be sustainable. Prenatal diagnosis is possible through real-time ultrasound studies as early as 12 weeks. Most reported cases die in utero, at birth, or in the newborn period. Advances in embryo/fetus pathology have led to the recognition of the many familial subtypes, allowing improved genetic counseling and early recognition in subsequent pregnancies.

Lissencéphalies : aspects cliniques et génétiques

The term lissencephaly covers a group of rare malformations sharing the common feature of anomalies in the appearance of brain convolutions (characterised by simplification or absence of folding) associated with abnormal organisation of the cortical layers as a result of neuronal migration defects during embryogenesis. Children with lissencephaly have feeding and swallowing problems, muscle tone anomalies (early hypotonia and subsequently limb hypertonia), seizures (in particular, infantile spasms) and severe psychomotor retardation. Multiple forms of lissencephaly have been described and their current classification is based on the associated malformations and underlying aetiology. Two large groups can be distinguished: classical lissencephaly (and its variants) and cobblestone lissencephaly. In classical lissencephaly (or type I), the cortex appears thickened, with four more or less disorganised layers rather than six normal layers. In the variants of classical lissencephaly, extra-cortical anomalies are also present (total or subtotal agenesis of the corpus callosum and/or cerebellar hypoplasia). The classical lissencephalies and the variant forms can be further divided into several subgroups. Four forms can be distinguished on the basis of their genetic aetiology: anomalies in the LIS1 gene (isolated lissencephaly and Miller-Dieker syndrome), anomalies in the TUBA3 and DCX genes, and lissencephalies caused by mutations in the ARX gene (XLAG syndrome, X-linked lissencephaly with agenesis of the corpus callosum). The incidence of all forms of type I lissencephaly is around 1 in 100,000 births. In addition to these four entities, isolated lissencephalies without a known genetic defect, lissencephalies with severe microcephaly (microlissencephaly) and lissencephalies associated with polymalformative syndromes are also included in the group of classical lissencephalies. Cobblestone lissencephaly (formally referred to as type II) is present in three entities: the Walker-Warburg, Fukuyama and MEB (Muscle-Eye-Brain) syndromes. It is characterised by global disorganisation of cerebral organogenesis with an uneven cortical surface (with a pebbled or cobblestone appearance). Microscopic examination reveals total disorganisation of the cortex and the absence of any distinguishable layers. Management is symptomatic only (swallowing problems require adapted feeding to prevent food aspiration, articular and respiratory physiotherapy to prevent orthopaedic problems resulting from hyptonia and treatment of gastrooesophageal reflux). The epilepsy is often resistant to treatment. The encephalopathy associated with lissencephaly is often very severe and affected children are completely dependent on the carer.

Human disorders of cortical development: from past to present

Epilepsy and mental retardation, originally of unknown cause, are now known to result from many defects including cortical malformations, neuronal circuitry disorders and perturbations of neuronal communication and synapse function. Genetic approaches in combination with MRI and related imaging techniques continually allow a re-evaluation and better classification of these disorders. Here we review our current understanding of some of the primary defects involved, with insight from recent molecular biology advances, the study of mouse models and the results of neuropathology analyses. Through these studies the molecular determinants involved in the control of neuron number, neuronal migration, generation of cortical laminations and convolutions, integrity of the basement membrane at the pial surface, and the establishment of neuronal circuitry are being elucidated. We have attempted to integrate these results with the available data concerning, in particular, human brain development, and to emphasize the limitations in some cases of extrapolating from rodent models. Taking such species differences into account is clearly critical for understanding the pathophysiological mechanisms associated with these disorders.

Genotypically defined lissencephalies show distinct pathologies

Lissencephaly is traditionally divided into 2 distinct pathologic forms: classic (type I) and cobblestone (type II). To date, mutations in 4 genes, LIS1, DCX, RELN, and ARX, have been associated with distinct type I lissencephaly syndromes. Each of these genes has been shown to play a role in normal cell migration, consistent with the presumed pathogenesis of type I lissencephaly. Based on these data, we hypothesized that all forms of radiographically defined type I lissencephaly independent of genotype would be pathologically similar. To test this hypothesis, we examined brains from 16 patients, including 15 lissencephalic patients and one patient with subcortical band heterotopia. Of these 16 patients, 6 had LIS1 deletions, 2 had DCX mutations, and 2 had ARX mutations. In addition, 6 patients had no defined genetic defect, although the patient with subcortical band heterotopia exhibited the same pattern of malformation expected with an XLIS mutation. In all cases, the cortex was thickened; however, the topographic distribution of the cortical pathology varied, ranging from frontal- to occipital-biased pathology to diffuse involvement of the neocortex. Although brains with LIS1 deletions exhibited the classic 4-layer lissencephalic architecture, patients with DCX and ARX mutations each had unique cytoarchitectural findings distinct from LIS1. Furthermore, 2 of the 5 patients with no known genetic defect showed a fourth type of histopathology characterized by a 2-layered cortex. Interestingly, the 2 brains with the fourth type of lissencephaly showed profound brainstem and cerebellar abnormalities. In summary, we identified at least 4 distinct histopathologic subtypes of lissencephaly that stratify with the underlying genetic defect. Based on these data, a new classification for lissencephaly is proposed that incorporates both pathologic and genetic findings.

The spectrum of type III lissencephaly: a clinicopathological update

A third type of lissencephaly that does not fufil diagnostic criteria of type I ("classical") and type II ("cobblestone") lissencephaly was described by our group as a new entity identified as OMIM 601160. This lethal familial syndrome comprises micrencephaly/lissencephaly and a spectrum of abnormalities lined to a severe fetal akinesia deformation sequence. Neuropathological findings suggest severe neurodegeneration leading to a marked neuronal dropout of the entire central nervous system and atrophy. Similar neuropathological findings have been described in the Neu-Laxova syndrome (NLS), an apparently different lethal malformation syndrome. Neuropathological similarities between OMIM 601160 and NLS raise the question of clinicopathological variability and genetic heterogeneity of type III lissencephaly. To answer this question, we compared our clinicopathological findings in a series of fetuses with OMIM 601160 to pathological data reported in NLS. In the study, 5 unrelated families with 7 affected fetuses were included. Interestingly, we found striking clinicopathological similarities between OMIM 601160 and NLS, which may represent a variability of a single neurodegenerative disease with early prenatal onset. Molecular studies in multiplex families defined through detailed clinicopathological screening are needed to clarify the distinction, if any, between these two entities.

Neocortical neuronal arrangement in LIS1 and DCX lissencephaly may be different

In type I or classical lissencephaly, two genetic causes, namely the LIS1 gene mapping at 17p13.3 and the DCX (doublecortin on X) gene mapping at Xq22.3 are involved. These are considered to act during corticogenesis on radial migratory pathways. The prevailing view is that heterozygous mutations in the LIS1 gene and hemizygous mutations in the DCX gene produce similar histological pattern. The present detailed neuropathological study in two unrelated fetuses with respectively a mutation in the LIS1 and the DCX genes do not confirm this view. In LIS1 mutation, the cortical ribbon displays a characteristic inverted organization, also called "four layered cortex" while in DCX mutation, the cortex displays a roughly ordered "six layered" lamination. Our hypothesis is that mutations of the LIS1 and DCX genes, may not affect the same neuronal arrangement in the neocortex. Because the pathology of proven XLIS is rarely documented, further detailed neuropathological analysis in other cases identified through molecular study would be of a great help in the recognition of neuronal population involved in these migrational disorders and their underlying molecular mechanism.

New syndrome of simplified gyral pattern, micromelia, dysmorphic features and early death

We report two sisters with a new syndrome of simplified gyral pattern, normal head circumference at birth but with subsequent development of microcephaly, intractable seizures, and early death. Dysmorphic features included coarse face, hypertrichosis, short nose, paranasal widening, long philtrum, short neck, upper limb micromelia, single transverse palmar lines, and clasp thumbs. The proband had repeated convulsions from shortly after birth and she required continuous artificial ventilation. Neurological examination showed absent sucking, rooting, Moro and grasping reflexes. MRI revealed a diffuse simplified gyral pattern with apparent agyria over the frontal lobes. Biochemical screening gave normal results. Her older sister had bilateral renal pelvic dilatation on prenatal ultrasound. She also developed severe convulsions on the first day of life, and she had to be artificially ventilated for 38 days. She had severe developmental retardation and neurological examination showed absence of spontaneous movements and Moro reflex, weak sucking reflex, and hypertonicity. CT scan of the brain showed a simplified gyral pattern. At 3 months, she developed hypocalcemia and hyperphosphatemia with normal levels of vitamin D and alkaline phosphatase, and parathyroid hormone level was low. Other biochemical tests gave normal results. She died at 5 months due to a massive aspiration event. Based on the unique clinical and radiological features found in our patients, we propose that this is a new syndrome.

Pena-Shokier phenotype: case presentation and review

Pena-Shokier phenotype is an early lethal disorder involving multiple joint contractures, facial anomalies, and pulmonary hypoplasia. Alternative terms for this syndrome used in the literature include fetal hypokinesia syndrome, lethal congenital contracture syndrome, and Pena-Shokier syndrome type I. The etiology for the early cases was attributed to neuromuscular disease, with deformations owing to weakness or paralysis of the motor unit. An abnormality of spinal cord motoneurons has been postulated in some cases. Pena-Shokier phenotype can also result from blockade of the neuromuscular junction, as shown by recent observations with women expressing antibodies against the fetal acetylcholine receptor. It has been shown that the Pena-Shokier phenotype may result from intrauterine cerebral dysfunction as well, including acquired brain insults and congenital brain malformations. The ultimate prognosis for children with this disorder is dependent on the underlying etiology and the severity of pulmonary disease. The authors report a fatal case of Pena-Shokier phenotype with congenital polymicrogyria. To our knowledge, the case presented is the first reported Pena-Shokier phenotype associated with this type of brain malformation.

Lissencephaly type III, stippled epiphyses and loose, thick skin: a new recessively inherited syndrome

We report on two new cases of syndromic lissencephaly in two consanguineous sibs, with skeletal abnormality, born to young, healthy, second cousin parents with healthy children. In Case 1, fetal ultrasound screening at 32 weeks of gestation showed microcephaly, skin infiltration and equinovarus feet. MRI disclosed cerebral agyria, hypoplastic cerebral mantle and posterior agenesis of the corpus callosum. The propositus, a boy, died soon after birth at term. In Case 2, fetal ultrasound study performed at 16 weeks of gestation disclosed skin infiltration. MRI at 22 weeks of gestation showed microcephaly with agenesis of corpus callosum and cerebellar hypoplasia. Pregnancy was terminated at 22 weeks of gestation. The fetus had normal 46, XY karyotype and similar anomalies found in the index case, with cranio-facial edema and arthrogryposis. X-ray films showed epiphyseal stippling of cervical vertebrae, feet and sacrum. Metacarpal bones were shortened with hypoplastic distal phalanges. Neuropathological findings were concordant with the pattern described in type III lissencephaly: an agyric brain with hypoplastic brain stem and cerebellum, severe neuronal loss of the cortical plate, matrix zone, basal ganglia, brainstem nuclei and spinal cord with axonal swelling and microcalcification. This entity seems to be a new syndromic lissencephaly type III, because of epiphyseal calcifications and metacarpophalangeal bone dysplasia.

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.