Fabio Torres

A new candidate locus for bilateral perisylvian polymicrogyria mapped on chromosome Xq27

Polymicrogyria (PMG) is characterized by an excessive number of small and prominent brain gyri, separated by shallow sulci. Bilateral perisylvian polymicrogyria (BPP) is the most common form of PMG. Clinical signs include pseudobulbar paresis, mental retardation, and epilepsy. Familial forms of BPP have been described and a candidate locus was previously mapped to chromosome Xq28, distal do marker DXS8103. The objective of this study was to perform linkage analysis in one family segregating BPP. A total of 15 individuals, including 8 affected patients with BPP were evaluated. Family members were examined by a neurologist and subjected to magnetic resonance imaging scans. Individuals were genotyped for 18 microsatellite markers, flanking a 42.3 cM interval on ch Xq27‐q28. Two‐point and multipoint linkage analysis was performed using the LINKAGE package and haplotype reconstruction was performed by GENEHUNTER software. Our results showed a wide spectrum of clinical manifestations in affected individuals with BPP, ranging from normal to mild neurological abnormalities. Two‐point linkage analysis yield a Zmax = 2.06 at θ = 0.00 for markers DXS1205 and DXS1227. Multipoint lod‐scores indicate a candidate interval of 13 cM between markers DSXS1205 and DXS8043, on ch Xq27.2‐Xq27.3. These results point to a new locus for BPP in a more centromeric location than previously reported.

Epileptic Features of Patients With Unilateral and Bilateral Schizencephaly

The extent of cortical maldevelopment might correlate with the severity of the clinical manifestation, such as cognitive delay or motor dysfunction. The objective of this study was to investigate the clinical features of epilepsy in patients with unilateral and bilateral schizencephaly. We studied 44 consecutive patients with schizencephaly diagnosed by magnetic resonance imaging (MRI). The epileptic features were analyzed in detail: frequency of epilepsy, median age at onset of epilepsy, semiology of seizures, characteristic features of electroencephalographic (EEG) abnormalities, epileptic syndromes, and antiepileptic drug treatment. We also verified the presence of motor disabilities. Data were analyzed according to the presence of unilateral or bilateral clefts and to the presence of open-lip versus closed-lip schizencephaly. We used the chi-square test and Fisher exact test for statistical analysis. Twenty-four patients had a unilateral cleft (group 1) and 20 patients had bilateral clefts (group 2). Ages ranged from 1 to 37 years (mean 10.6 years). Epilepsy was present in 15 (63%) patients in group 1 and in 11 (55%) patients of group 2; a history of status epilepticus occurred in 13% of group 1 and in 27% in group 2; and a history of clusters of seizures occurred in 40% of group 1 and in 45% of group 2. Eight (53%) patients in group 1 and 6 (54%) patients in group 2 were in monotherapy. Ten (67%) patients in group 1 and 7 (64%) patients in group 2 had seizures controlled with antiepileptic drugs. The frequency of EEG abnormalities was similar between groups (75% and 85%, groups 1 and 2, respectively). Statistical analysis showed no difference between the two groups in the variables mentioned above. However, motor disability was significantly more frequent and more severe in group 2. Regarding the type of schizencephaly (open lip versus closed lip), there was no difference in the frequency of patients with epilepsy, and severe motor deficit was more frequently found in bilateral and open-lip schizencephaly. The extent of the cortical maldevelopment in patients with schizencephaly does not correlate with the severity of the clinical and EEG features of epilepsy, unlike the cognitive and motor manifestations. In addition, the type of schizencephaly (open lip versus closed lip) does not correlate with the presence of epilepsy or seizure control, unlike motor deficit. (J Child Neurol 2006;21:757—760; DOI 10.2310/7010.2006.00173).

Infratentorial gray matter atrophy and excess in primary craniocervical dystonia

BACKGROUND Primary craniocervical dystonia (CCD) is generally attributed to functional abnormalities in the cortico-striato-pallido-thalamocortical loops, but cerebellar pathways have also been implicated in neuroimaging studies. Hence, our purpose was to perform a volumetric evaluation of the infratentorial structures in CCD. METHODS We compared 35 DYT1/DYT6 negative patients with CCD and 35 healthy controls. Cerebellar volume was evaluated using manual volumetry (DISPLAY software) and infratentorial volume by voxel based morphometry of gray matter (GM) segments derived from T1 weighted 3 T MRI using the SUIT tool (SPM8/Dartel). We used t-tests to compare infratentorial volumes between groups. RESULTS Cerebellar volume was (1.14 ± 0.17) × 10(2) cm(3) for controls and (1.13 ± 0.14) × 10(2) cm(3) for patients; p = 0.74. VBM demonstrated GM increase in the left I-IV cerebellar lobules and GM decrease in the left lobules VI and Crus I and in the right lobules VI, Crus I and VIIIb. In a secondary analysis, VBM demonstrated GM increase also in the brainstem, mostly in the pons. CONCLUSION While gray matter increase is observed in the anterior lobe of the cerebellum and in the brainstem, the atrophy is concentrated in the posterior lobe of the cerebellum, demonstrating a differential pattern of infratentorial involvement in CCD. This study shows subtle structural abnormalities of the cerebellum and brainstem in primary CCD.

Diffuse Decreased Gray Matter in Patients with Idiopathic Craniocervical Dystonia: A Voxel-Based Morphometry Study

Background: Recent studies have addressed the role of structures other than the basal ganglia in the pathophysiology of craniocervical dystonia (CCD). Neuroimaging studies have attempted to identify structural abnormalities in CCD but a clear pattern of alteration has not been established. We performed whole-brain evaluation using voxel-based morphometry (VBM) to identify patterns of gray matter (GM) changes in CCD. Methods: We compared 27 patients with CCD matched in age and gender to 54 healthy controls. VBM was used to compare GM volumes. We created a two-sample t-test corrected for subjects’ age, and we tested with a level of significance of p < 0.001 and false discovery rate (FDR) correction (p < 0.05). Results: Voxel-based morphometry demonstrated significant reductions of GM using p < 0.001 in the cerebellar vermis IV/V, bilaterally in the superior frontal gyrus, precuneus, anterior cingulate and paracingulate, insular cortex, lingual gyrus, and calcarine fissure; in the left hemisphere in the supplementary motor area, inferior frontal gyrus, inferior parietal gyrus, temporal pole, supramarginal gyrus, rolandic operculum, hippocampus, middle occipital gyrus, cerebellar lobules IV/V, superior, and middle temporal gyri; in the right hemisphere, the middle cingulate and precentral gyrus. Our study did not report any significant result using the FDR correction. We also detected correlations between GM volume and age, disease duration, duration of botulinum toxin treatment, and the Marsden–Fahn dystonia scale scores. Conclusion: We detected large clusters of GM changes chiefly in structures primarily involved in sensorimotor integration, motor planning, visuospatial function, and emotional processing.

Mutation screening in a cohort of patients with lissencephaly and subcortical band heterotopia

The authors describe clinical, neuroimaging and molecular findings in a group of 15 patients with classic lissencephaly (LIS) and subcortical band heterotopia (SBH). A 1385A→C mutation was found in the LIS1 gene in one patient with LIS more severe than expected for individuals with missense mutations in LIS1. The authors believe that the site of the mutation, present in a functionally critical region of the protein, could explain the unusual severe phenotype found in this patient.

Clinical and Genetic Heterogeneity in Familial Temporal Lobe Epilepsy

Summary:  Purpose: Familial forms of temporal lobe epilepsy have been described recently. A locus on ch 10q has been linked to partial epilepsy with auditory symptoms. We investigated the proportion of families segregating temporal lobe epilepsy (TLE) linked to ch 10q and sought to establish genotype–phenotype correlations.

LINKGEN: a new algorithm to process data in genetic linkage studies.

Genetic linkage studies using whole genome scans are useful approaches for identifying genes related to human diseases. In general, these studies require genotyping of a large number of markers, which are used in statistical analysis. Recent technology has allowed easy genotyping of a large number of markers in less time; therefore, interface programs are required for manipulation of these large data sets. We present a new algorithm, which processes input data in LINKAGE format from data analyzed by automated genotyping systems. The algorithm was implemented in PERL script and R environment. Validation was performed with genotyped data from 127 individuals and 720 microsatellite markers of two whole genome scans. Our results showed a significant decrease in data processing time. In addition, this algorithm provides unbiased allele frequency estimation used for linkage analysis. LINKGEN is a freely available online tool and allows easier, faster, and reliable manipulation of large genotyping data sets.

MicroRNA hsa-miR-134 is a circulating biomarker for mesial temporal lobe epilepsy

Epilepsy is misdiagnosed in up to 25% of patients, leading to serious and long-lasting consequences. Recently, circulating microRNAs have emerged as potential biomarkers in a number of clinical scenarios. The purpose of this study was to identify and to validate circulating microRNAs that could be used as biomarkers in the diagnosis of epilepsy. Quantitative real-time PCR was used to measure plasma levels of three candidate microRNAs in two phases of study: an initial discovery phase with 14 patients with mesial temporal lobe epilepsy (MTLE), 13 with focal cortical dysplasia (FCD) and 16 controls; and a validation cohort constituted of an independent cohort of 65 patients with MTLE and 83 controls. We found hsa-miR-134 downregulated in patients with MTLE (p = 0.018) but not in patients with FCD, when compared to controls. Furthermore, hsa-miR-134 expression could be used to discriminate MTLE patients with an area under the curve (AUC) of 0.75. To further assess the robustness of hsa-miR-134 as a biomarker for MTLE, we studied an independent cohort of 65 patients with MTLE, 27 of whom MTLE patients were responsive to pharmacotherapy, and 38 patients were pharmacoresistant and 83 controls. We confirmed that hsa-miR-134 was significantly downregulated in the plasma of patients with MTLE when compared with controls (p < 0.001). In addition, hsa-miR-134 identified patients with MTLE regardless of their response to pharmacotherapy or the presence of MRI signs of hippocampal sclerosis. We revealed that decreased expression of hsa-miR-134 could be a potential non-invasive biomarker to support the diagnosis of patients with MTLE.

17p13.3 Microdeletion: Insights on Genotype-Phenotype Correlation

Microdeletions in the chromosomal region 17p13.3 are associated with neuronal migration disorders, and PAFAB1H1 is the main gene involved. The largest genomic imbalances, including the YWHAE and CRK genes, cause more severe structural abnormalities of the brain and other associated dysmorphic features. Here, we describe a 3-year-old boy with a microdeletion in 17p13.3 presenting with minor facial dysmorphisms, a cleft palate, neurodevelopmental delay, and behavioral disorder with no structural malformation of the brain. The patient was evaluated by a clinician using a standard protocol. Laboratory investigation included GTG-banding, whole-genome AGH, and array-CGH. Whole-genome AGH and array-CGH analysis identified an estimated 2.1-Mb deletion in the 17p13.3 region showing haploinsufficiency of the YWHAE, CRK, H1C1, and OVCA1 genes and no deletion of PAFAH1B1. The complex gene interaction on brain development and function is illustrated in the genotype-phenotype correlation described here. This report reinforces the importance of the 17p13.3 region in developmental abnormalities and highlights the weak implication of the HIC1 and OVCA1 genes in palatogenesis.

Ancestry Informative Marker Panel to Estimate Population Stratification Using Genome-wide Human Array

Case‐control studies are a powerful strategy to identify candidate genes in complex diseases. In admixed populations, association studies can be affected by population stratification, leading to spurious genetic associations. Ancestry informative markers (AIMs) can be used to minimise this effect. The aim of this work was to select a set of AIMs to estimate population stratification in a Brazilian case‐control study performed using a genome‐wide array. A total of 345 single nucleotide polymorphism (SNP) AIMs, selected from the Cytoscan HD array and based on previously reported panels, was used to discriminate between European, African, and Amerindian populations. These SNP‐AIMs were used to infer ancestry in systemic lupus erythematosus (SLE) patients (n  =  23) and in healthy subjects (n  =  110). Moderate population substructure was observed between SLE and control groups (Fst  =  0.0113). Although patients and controls have shown a major European genomic contribution, significant differences in the European (P  =  6.47 × 10−5) and African (P  =  1.14 × 10−3) ancestries were detected between the two groups. We performed a two‐step validation of the 345 SNP‐AIMs panel estimating the ancestral contributions using a panel of 12 AIMs and approximately 70K SNPs from the array. Evaluation of population substructure in case‐control studies, avoiding spurious genetic associations, can be performed using our panel of 345 SNP‐AIMs.