Males with epilepsy,complete subcortical band heterotopia,and somatic mosaicism for DCX

Subcortical band heterotopia (SBH) is seen predominantly in females, resulting from mutations in the X-linked doublecortin (DCX) gene, and can present with mild mental retardation and epilepsy. Males carrying DCX mutations usually demonstrate lissencephaly and are clinically much more severely affected. This article reports two cases of males with SBH indistinguishable from the female phenotype, both resulting from somatic mosaicism for DCX mutation.     

Subcortical laminar heterotopia and lissencephaly in two families: a single X linked dominant gene.

Neuronal migration disorders can now be recognised by MRI. This paper reports two families in which the mothers had subcortical laminar heterotopia and four of their children had either similar heterotopia (two girls) or severe pachygyria or lissencephaly (two boys). Laminar heterotopia was more evident on MRI T2 weighted images. The patients had mild to severe epilepsy and mental retardation depending on the extent of cortical abnormalities. In these families, subcortical laminar heterotopia, pachygyria, and lissencephaly seem to share the same X linked or autosomal dominant gene. No chromosomal abnormalities, especially of chromosome 17, could be identified. For appropriate genetic counselling of the family of a child with lissencephaly or subcortical laminar heterotopia, MRI should be performed in parents or siblings with mental retardation or epilepsy.     

Familial periventricular heterotopia: missense and distal truncating mutations of the FLN1 gene

OBJECTIVE: To examine the clinical and MRI associations in bilateral periventricular nodular heterotopia (BPNH) (MIM # 300049) in two families segregating a missense mutation and a C-terminal deletion of the filamin 1(FLN1) gene. BACKGROUND: Classical familial BPNH, an X-linked dominant disorder, has been associated with protein truncations or splicing mutations, which tend to cluster at the N-terminal of the FLN1 protein, causing severe predicted loss of the protein function. The clinical syndrome includes symmetrical contiguous nodular heterotopia lining the lateral ventricles, epilepsy, mild retardation to normal cognitive level in affected females, and prenatal lethality in hemizygous boys. METHODS: Clinical examination, cognitive testing, MRI, mutation analysis (direct sequencing, single-strand conformation polymorphism) in seven patients from two families with BPNH. RESULTS: In Family 1, harboring an A > T change in exon 2 (E82V), heterotopic nodules were few, asymmetric, and noncontiguous. Five boys born from affected females had died unexpectedly early in life. In Family 2, harboring an 8 base pair deletion in exon 47 (7627_7634del TGTGCCCC), heterotopic nodules were thick and contiguous. Affected females in both families showed normal to borderline IQ and epilepsy. CONCLUSION: Missense mutations and distal truncations consistent with partial loss of FLN1 function cause familial BPNH with the classical clinical phenotype including epilepsy and mild mental retardation, if any. However, missense mutations have milder anatomic consequences in affected females and are possibly compatible with live birth but short survival of boys.     

Epileptogenic brain malformations: clinical presentation, malformative patterns and indications for genetic testing.

We review here those malformations of the cerebral cortex which are most often observed in epilepsy patients, for which a genetic basis has been elucidated or is suspected and give indications for genetic testing. There are three forms of lissencephaly (agyria-pachygyria) resulting from mutations of known genes, which can be distinguished because of their distinctive imaging features. They account for about 85% of all lissencephalies. Lissencephaly with posteriorly predominant gyral abnormality is caused by mutations of the LIS1 gene on chromosome 17. Anteriorly predominant lissencephaly in hemizygous males and subcortical band heterotopia (SBH) in heterozygous females are caused by mutations of the XLIS(or DCX) gene. Mutations of the coding region of XLIS were found in all reported pedigrees, and in most sporadic female patients with SBH. Missense mutations of both LIS1 and XLIS genes have been observed in some of the rare male patients with SBH. Autosomal recessive lissencephaly with cerebellar hypoplasia has been associated with mutations of the reelin gene. With few exceptions, children with lissencephaly have severe developmental delay and infantile spasms early in life. Patients with SBH have a mild to severe mental retardation with epilepsy of variable severity and type. X-linked bilateral periventricular nodular heterotopia (BPNH) consists of typical BPNH with focal epilepsy in females and prenatal lethality in males. About 88% of patients have focal epilepsy. Filamin A (FLNA) mutations have been reported in some families and in sporadic patients. Additional, possibly autosomal recessive gene(s) are likely to be involved in causing BPNH non-linked to FLN1. Tuberous sclerosis (TS) is a dominant disorder caused by mutations in at lest two genes, TSC1 and TSC2. 75% of cases are sporadic. Most patients with TS have epilepsy. Infantile spasms are a frequent early manifestation of TS. Schizencephaly (cleft brain) has a wide anatomo-clinical spectrum, including focal epilepsy in most patients. Familial occurrence is rare. Heterozygous mutations in the EMX2 gene have been reported in some patients. However, at present, there is no clear indication on the possible pattern of inheritance and on the practical usefulness that mutation detection in an individual with schizencephaly would carry in terms of genetic counselling. Amongst several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria had familial occurrence on several occasions. Genetic heterogeneity is likely, including autosomal recessive, X-linked dominant, X-linked recessive inheritance and association to 22q11.2 deletions. FISH analysis for 22q11.2 is advisable in all patients with perisylvian polymicrogyria. Parents of an affected child with normal karyotype should be given up to a 25% recurrence risk.     

Incomplete penetrance with normal MRI in a woman with germline mutation of the DCX gene

X-linked isolated lissencephaly sequence (ILS) and subcortical band heterotopia are allelic human disorders associated with mutations of the DCX gene in both familial and sporadic forms. The authors describe a large Sardinian family in which three brothers with ILS have a missense mutation of the DCX gene. Their mother, a nonmosaic carrier, has a normal phenotype and cranial MRI. Skewed X-inactivation in the lymphocytes was also ruled out. This is the first report of an asymptomatic carrier of a DCX mutation likely due to apparent nonpenetrance.     

Somatic mosaicism and variable penetrance in doublecortin-associated migration disorders

X-linked isolated lissencephaly sequence (XLIS) and subcortical band heterotopia (SBH) are allelic disorders caused by mutations in the doublecortin (DCX) gene. This genetic analysis of seven families revealed four novel mutations in the DCX gene. The authors detected a high rate of somatic mosaicism in male and female patients with variable penetrance of bilateral SBH including nonpenetrance in a heterozygous woman. In addition, the authors implemented prenatal diagnosis in a family with SBH/XLIS.     

Epileptogenic brain malformations: radiological and clinical presentation and indications for genetic testing

Malformations of cortical development (MCD) represent a major cause of developmental disabilities and severe epilepsy. Advances in imaging and genetics have improved the diagnosis and classification of these conditions. Up to now, eight genes have been involved in different types of MCD. Lissencephaly-pachygyria and subcortical band heterotopia (SBH) represent a malformative spectrum resulting from mutations of either LIS1 or DCX genes. LIS1 mutations cause a more severe malformation in the posterior brain regions. DCX mutations usually cause anteriorly predominant lissencephaly in males and SBH in female patients. Additional forms are X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia associated with mutations of the ARX gene. Lissencephaly with cerebellar hypoplasia (LCH) encompass heterogeneous disorders named LCH type a to d. LCHa are related with mutation in LIS1 or DCX, LCHb with mutation of RELN gene, and LCHd could be related with TUBA1A gene. Polymicrogyria encompass a wide range of clinical, aetiological and histological findings. Among several syndromes, recessive bilateral fronto-parietal polymicrogyria has been associated with mutations of the GPR56 gene. Bilateral perisylvian polymicrogyria showed a linkage to chromosome Xq28 in some pedigrees, and mutations in SRPX2 gene in others conditions. X-linked bilateral periventricular nodular heterotopia (BPNH) consists of BPNH with focal epilepsy in females and prenatal lethality in males. Filamin A (FLNA) mutations have been reported in some families and in sporadic patients. It is possible to infer the most likely causative gene by brain imaging studies and other clinical findings. Based on this experience, a detailed phenotype analysis is needed to develop the most efficient research on MCD in the future.     

Fiber tractography assessment in double cortex syndrome

Introduction  

Subcortical band heterotopia (SBH) or double cortex syndrome is a malformation of cortical development that may be related to intractable epilepsy and severe mental retardation or to mild epilepsy and slight mental delay or normal cognitive functions. Several studies have been performed using neuroradiological or neurophysiological techniques, like SPECT, PET, MRS, fMRI, and MEG, in attempt to better characterize this neuronal migration disorder. Recently, also diffusion tensor imaging (DTI) and fiber tracking (FT) have been used to investigate on white matter anomalies in SBH, adding more information about such gray matter anomaly.     

Neuronal migration disorders, genetics, and epileptogenesis

Several malformation syndromes with abnormal cortical development have been recognized. Specific causative gene defects and characteristic electroclinical patterns have been identified for some. X-linked periventricular nodular heterotopia is mainly seen in female patients and is often associated with focal epilepsy. FLN1 mutations have been reported in all familial cases and in about 25% of sporadic patients. A rare recessive form of periventricular nodular heterotopia owing to ARGEF2 gene mutations has also been reported in children with microcephaly, severe delay, and early-onset seizures. Lissencephaly-pachygyria and subcortical band heterotopia represent a malformative spectrum resulting from mutations of either the LIS1 or the DCX (XLIS) gene. LIS1 mutations cause a more severe malformation posteriorly. Most children have severe developmental delay and infantile spasms, but milder phenotypes are on record, including posterior subcortical band heterotopia owing to mosaic mutations of LIS1. DCX mutations usually cause anteriorly predominant lissencephaly in male patients and subcortical band heterotopia in female patients. Mutations of the coding region of DCX were found in all reported pedigrees and in about 50% of sporadic female patients with subcortical band heterotopia. Mutations of XLIS have also been found in male patients with anterior subcortical band heterotopia and in female patients with normal brain magnetic resonance imaging. The thickness of the band and the severity of pachygyria correlate with the likelihood of developing severe epilepsy. Autosomal recessive lissencephaly with cerebellar hypoplasia, accompanied by severe delay, hypotonia, and seizures, has been associated with mutations of the reelin (RELN) gene. X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia in genotypic males is associated with mutations of the ARX gene. Affected boys have severe delay and infantile spasms with suppression-burst electroencephalograms. Early death is frequent. Carrier female patients can have isolated corpus callosum agenesis. Schizencephaly has a wide anatomoclinical spectrum, including focal epilepsy in most patients. Familial occurrence is rare. Initial reports of heterozygous mutations in the EMX2 gene have not been confirmed. Among several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria shows genetic heterogeneity, including linkage to chromosome Xq28 in some pedigrees, autosomal dominant or recessive inheritance in others, and an association with chromosome 22q11.2 deletion in some patients. About 65% of patients have severe epilepsy. Recessive bilateral frontoparietal polymicrogyria has been associated with mutations of the GPR56 gene.     

Novel mental retardation-epilepsy syndrome linked to Xp21.1-p11.4.

We evaluated a kindred with X-linked mental retardation and epilepsy. Seven affected males with mild to moderate mental retardation developed seizures (primarily generalized, tonic-clonic, and atonic) that began on average at 6.8 months of age (range, 4 to 14 months). These patients did not have a history of infantile spasms. There were no dysmorphic features. Other than mental retardation, the neurological examination was unremarkable, with exception of 2 affected subjects who had mild generalized rigidity and ataxia. We identified tight linkage to a group of markers on Xp21.1-p11.4. A maximum two-point LOD score of +3.83 at straight theta = 0 was obtained for markers DXS8090, DXS1069, DXS8102, and DXS8085. This locus spans 7.7cM between DXS1049 and DXS8054 and does not overlap the locus for X-linked West syndrome. The tetraspanin gene, implicated in nonspecific mental retardation, is mapped to this region. We sequenced the tetraspanin coding sequence in subjects with X-linked mental retardation and epilepsy and did not identify disease-specific mutations. The syndrome we describe, designated X-linked mental retardation and epilepsy, is clinically and genetically distinct from X-linked West syndrome and other X-linked mental retardation-epilepsy syndromes.     

X-linked lissencephaly with absent corpus callosum and ambiguous genitalia (XLAG): clinical, magnetic resonance imaging, and neuropathological findings

X-linked lissencephaly with absent corpus callosum and ambiguous genitalia is a newly recognized syndrome responsible for a severe neurological disorder of neonatal onset in boys. Based on the observations of 3 new cases, we confirm the phenotype in affected boys, describe additional MRI findings, report the neuropathological data, and show that carrier females may exhibit neurological and magnetic resonance imaging abnormalities. In affected boys, consistent clinical features of X-linked lissencephaly with absent corpus callosum and ambiguous genitalia are intractable epilepsy of neonatal onset, severe hypotonia, poor responsiveness, genital abnormalities, and early death. On magnetic resonance imaging, a gyration defect consisting of anterior pachygyria and posterior agyria with a moderately thickened brain cortex, dysplastic basal ganglia and complete agenesis of the corpus callosum are consistently found. Neuropathological examination of the brain shows a trilayered cortex containing exclusively pyramidal neurons, a neuronal migration defect, a disorganization of the basal ganglia, and gliotic and spongy white matter. Finally, females related to affected boys may have mental retardation and epilepsy, and they often display agenesis of the corpus callosum. These findings expand the phenotype of X-linked lissencephaly with absent corpus callosum and ambiguous genitalia, may help in the detection of carrier females in affected families, and give arguments for a semidominant X-linked mode of inheritance.     

Genetic Malformations of the Cerebral Cortex and Epilepsy

Summary:  We reviewed the epileptogenic cortical malformations for which a causative gene has been cloned or a linkage obtained. X-linked bilateral periventricular nodular heterotopia (BPNH) consists of typical BPNH with epilepsy in female patients and prenatal lethality in most males. About 90% of patients have focal epilepsy. Filamin A mutations have been reported in all families and in ∼20% of sporadic patients. A rare recessive form of BPNH also has been reported. Most cases of lissencephaly–pachygyria are caused by mutations of LIS1 and XLIS genes. LIS1 mutations cause a more severe malformation posteriorly. Most children have isolated lissencephaly, with severe developmental delay and infantile spasms, but milder phenotypes have been recorded. XLIS usually causes anteriorly predominant lissencephaly in male patients and subcortical band heterotopia (SBH) in female patients. Thickness of the band and severity of pachygyria correlate with the likelihood of developing Lennox–Gastaut syndrome. Mutations of the coding region of XLIS are found in all reported pedigrees and in 50% of sporadic female patients with SBH. Autosomal recessive lissencephaly with cerebellar hypoplasia; accompanied by severe delay, hypotonia, and seizures, has been associated with mutations of the RELN gene. Schizencephaly has a wide anatomoclinical spectrum, including focal epilepsy in most patients. Familial occurrence is rare. Initial reports of heterozygous mutations in the EMX2 gene need confirmation. Among several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria shows genetic heterogeneity, including linkage to Xq28 in some pedigrees, autosomal recessive inheritance in others, and association with 22q11.2 deletion in some patients. About 65% of patients have severe epilepsy, often Lennox–Gastaut syndrome. Recessive bilateral frontal polymicrogyria has been linked to chromosome 16q12.2–21.     

Turner syndrome and schizophrenia: A further hint for the role of the X-chromosome in the pathogenesis of schizophrenic disorders

Abnormalities of sex chromosomes are associated with various forms of neuropsychiatric disorders, such as schizophrenia. Turner syndrome occurs approximately threefold more frequently in female schizophrenics compared to the general female population. A single case is reported. We report on a case of a 41-year-old woman with Turner syndrome, schizophrenia, mental retardation, and hypothyroidism. A polymorphism of the HOPA gene within Xq13 termed HOPA^12bp is associated with schizophrenia, mental retardation, and hypothyroidism. Interestingly, Xq13 is the X-chromosome region that contains the X-inactivation center and a gene escaping X-inactivation whose gene product may be involved in the X-inactivation process as well as in the pathogenesis of sex chromosome anomalies such as Turner syndrome. These genes that escape X-inactivation may produce their gene products in excess, influencing normal brain growth and differentiation. Our case gives a further hint for an involvement of the X-chromosome in the pathogenesis of schizophrenia.     

Voxel-based 3D MRI analysis helps to detect subtle forms of subcortical band heterotopia

PURPOSE: To evaluate the potential diagnostic value of a novel magnetic resonance image (MRI) postprocessing technique in subtle forms of subcortical band heterotopia (SBH). The method was introduced to improve the visualization of blurred gray-white matter junctions associated with focal cortical dysplasia but was found to be applicable also to SBH. METHODS: In the voxel-based MRI analysis presented here, T1-weighted MRI volume data sets are normalized and segmented using standard algorithms of SPM5. The distribution of gray and white matter is analyzed on a voxelwise basis and compared with a normal database of 150 controls. Based on this analysis, a three-dimensional feature map is created that highlights brain areas if their signal intensities fall within the range between normal gray and white matter and differ from the normal database in this respect. The method was applied to the MRI data of 378 patients with focal epilepsy in three different epilepsy centers. RESULTS: SBH was diagnosed in seven patients with five of them showing subtle forms of SBH that had gone unrecognized in conventional visual analysis of MRI and were only detected by MRI postprocessing. In contrast to distinct double cortex syndrome, these patients had partial double cortex with SBH mostly confined to posterior brain regions. CONCLUSIONS: The results of this study suggest that a considerable part of cases with SBH might remain unrecognized by conventional MRI. Voxel-based MRI analysis may help to identify subtle forms and appears to be a valuable additional diagnostic tool in the evaluation of patients with cryptogenic epilepsy.     

Gray matter heterotopia

Gray matter heterotopia are common malformations of cortical development. From a clinical perspective, affected patients are best divided into three groups: subependymal, subcortical, and band heterotopia (also called double cortex). Symptomatic women with subependymal heterotopia typically present with partial epilepsy during the second decade of life; development and neurologic examinations up to that point are typically normal. Symptoms in men with subependymal heterotopia vary, depending on whether they have the X-linked or autosomal form. Men with the X-linked form more commonly have associated CNS and visceral anomalies; their development is typically abnormal. Symptomatic men with the autosomal variety have clinical courses similar to symptomatic women. Both men and women with subcortical heterotopia typically have congenital fixed neurologic deficits and develop partial epilepsy during the second half of the first decade of life. The more extensive the subcortical heterotopia, the greater the deficit; bilateral heterotopia are almost invariably associated with severe developmental delay or mental retardation. In general, band heterotopia are seen exclusively in women; men with a mutation of the related gene (called XLIS or DCX) usually die in utero or have a much more severe brain anomaly. Symptoms in affected women vary from normal to severe developmental delay or mental retardation; the severity of the syndrome is related to the thickness of the band of arrested neurons. Nearly all affected patients that come to medical attention have epilepsy, with partial complex and atypical absence epilepsy being the most common syndromes. Some of the more severely affected patients develop attacks.     

Four Caucasian patients with mutations in the fukutin gene and variable clinical phenotype

Fukuyama congenital muscular dystrophy (FCMD) is frequent in Japan, due to a founder mutation of the fukutin gene (FKTN). Outside Japan, FKTN mutations have only been reported in a few patients with a wide spectrum of phenotypes from Walker–Warburg syndrome to limb-girdle muscular dystrophy (LGMD2M). We studied four new Caucasian patients from three unrelated families. All showed raised serum CK initially isolated in one case and muscular dystrophy. Immunohistochemical studies and haplotype analysis led us to search for mutations in FKTN. Two patients (two sisters) presented with congenital muscular dystrophy, mental retardation, and posterior fossa malformation including cysts, and brain atrophy at Brain MRI. The other two patients had normal intelligence and brain MRI. Sequencing of the FKTN gene identified three previously described mutations and two novel missense mutations. Outside Japan, fukutinopathies are associated with a large spectrum of phenotypes from isolated hyperCKaemia to severe CMD, showing a clear overlap with that of FKRP.     

Focal Pachypolymicrogyria in Three Siblings

The malformation of focal pachypolymicrogyria might be the manifestation of an X-linked recessive disorder according to the results of this study. Three siblings revealed focal pachypolymicrogyria on magnetic resonance imaging (MRI) and had a strong family history of epilepsy and mental retardation. All three siblings had the same mother; the father of Patient 1 was not related to the mother, but the father of Patients 2 and 3 was related to her. The MRI of the father of Patients 2 and 3 demonstrated focal pachypolymicrogyria. The mother’s MRI was normal. In this family, epilepsy or mental retardation was found mainly in the males (Patient 3 was an exception), and they were all born to female members of this family, not male. Patient 3 was probably a homozygote with an X-linked recessive inheritance, and therefore, she demonstrated the most severe clinical findings.     

Diffuse subcortical band heterotopia,periodic limb movements during sleep and a novel “de novo” mutation in the DCX gene

Mutations of the DCX gene (Xp22.3) cause X-linked lissencephaly in males and double cortex syndrome (DCS) or subcortical band heterotopia (SBH) in females. SBH is characterized by bilateral bands of grey matter interposed in the white matter between the cortex and the lateral ventricles. The main clinical manifestation in patients with SBH is epilepsy, which may be partial or generalized and is intractable in approximately 65% of the patients. An association of periodic limb movements (PLMs) and SBH has not been documented previously. We describe a 2-year-old girl affected by SBH with epilepsy and periodic limb movements (PLMs), in whom a novel “de novo” missense substitution, Met1Val (M1V), was identified in the DCX gene. Physiopathological links between PLMs and SBH are discussed.     

Aicardi syndrome: follow-up investigation of Swedish children born in 1975-2002

Aicardi syndrome has been defined by the triad of agenesis of the corpus callosum, early seizure onset and lacunar chorioretinopathy. In a nation-wide survey a total of 18 Swedish cases were found. Fourteen girls were re-examined by one of the authors at the ages of 1-27 years. One was seizure free following epilepsy surgery operation, 13 were drug resistant. Two were on ketogenic diet. Most of the girls had multifocal EEG discharges. All except one were severely disabled with severe mental retardation and total dependency on helpers for activities of daily life. Communication, nutrition, and motor function were severely affected areas. Visual function was difficult to evaluate because of mental retardation and lack of co-operation and varied from severely impaired to normal. In one case the appearance of the ocular fundus was documented to have changed with time. One girl was exceptional and seizure free with mild mental retardation. An update by March 2006 showed that 12/18 patients were still alive, at a median age of 13.5 years (range: 3-31 years). Six had died between the ages of 3-10 years. They had all suffered from intractable epilepsy and belonged to the most disabled group. Surprisingly two had died from malignant brain tumours.     

Fixation-off sensitivity and generalized epileptic EEG induced by eyes closed

This report describes a female with eyelid fluttering with absence seizures, infrequent generalized tonic-clonic seizures, and mild mental retardation. Interictal and video-electroencephalography evaluations revealed normal activity while eyes were open but continuous generalized discharges with eyes closed (eyes closed induced abnormality), as well as fixation-off sensitivity. This patient is in the group of a pure and distinct clinical form of fixation-off sensitivity cryptogenic generalized epilepsy.