Estimating heritability and its enrichment in tissue-specific gene sets in admixed populations

It is important to study the genetics of complex traits in diverse populations. Here, we introduce covariate-adjusted linkage disequilibrium (LD) score regression (cov-LDSC), a method to estimate SNP-heritability (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\boldsymbol{h}}_{\boldsymbol{g}}^{\mathbf{2}})$\end{document} and its enrichment in homogenous and admixed populations with summary statistics and in-sample LD estimates. In-sample LD can be estimated from a subset of the genome-wide association studies samples, allowing our method to be applied efficiently to very large cohorts. In simulations, we show that unadjusted LDSC underestimates \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\boldsymbol{h}}_{\boldsymbol{g}}^{\mathbf{2}}$\end{document} by 10–60% in admixed populations; in contrast, cov-LDSC is robustly accurate. We apply cov-LDSC to genotyping data from 8124 individuals, mostly of admixed ancestry, from the Slim Initiative in Genomic Medicine for the Americas study, and to approximately 161 000 Latino-ancestry individuals, 47 000 African American-ancestry individuals and 135 000 European-ancestry individuals, as classified by 23andMe. We estimate \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\boldsymbol{h}}_{\boldsymbol{g}}^{\mathbf{2}}$\end{document} and detect heritability enrichment in three quantitative and five dichotomous phenotypes, making this, to our knowledge, the most comprehensive heritability-based analysis of admixed individuals to date. Most traits have high concordance of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\boldsymbol{h}}_{\boldsymbol{g}}^{\mathbf{2}}$\end{document} and consistent tissue-specific heritability enrichment among different populations. However, for age at menarche, we observe population-specific heritability estimates of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\boldsymbol{h}}_{\boldsymbol{g}}^{\mathbf{2}}$\end{document}. We observe consistent patterns of tissue-specific heritability enrichment across populations; for example, in the limbic system for BMI, the per-standardized-annotation effect size \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$ \tau $\end{document}^* is 0.16 ± 0.04, 0.28 ± 0.11 and 0.18 ± 0.03 in the Latino-, African American- and European-ancestry populations, respectively. Our approach is a powerful way to analyze genetic data for complex traits from admixed populations.

Genetic variation at the glycosaminoglycan metabolism pathway contributes to the risk of psoriatic arthritis but not psoriasis

OBJECTIVE

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis affecting up to 30% of patients with psoriasis (Ps). To date, most of the known risk loci for PsA are shared with Ps, and identifying disease-specific variation has proven very challenging. The objective of the present study was to identify genetic variation specific for PsA.

METHODS

We performed a genome-wide association study in a cohort of 835 patients with PsA and 1558 controls from Spain. Genetic association was tested at the single marker level and at the pathway level. Meta-analysis was performed with a case-control cohort of 2847 individuals from North America. To confirm the specificity of the genetic associations with PsA, we tested the associated variation using a purely cutaneous psoriasis cohort (PsC, n=614) and a rheumatoid arthritis cohort (RA, n=1191). Using network and drug-repurposing analyses, we further investigated the potential of the PsA-specific associations to guide the development of new drugs in PsA.

RESULTS

We identified a new PsA risk single-nucleotide polymorphism at B3GNT2 locus (p=1.10e-08). At the pathway level, we found 14 genetic pathways significantly associated with PsA (p_FDR<0.05). From these, the glycosaminoglycan (GAG) metabolism pathway was confirmed to be disease-specific after comparing the PsA cohort with the cohorts of patients with PsC and RA. Finally, we identified candidate drug targets in the GAG metabolism pathway as well as new PsA indications for approved drugs.

CONCLUSION

These findings provide insights into the biological mechanisms that are specific for PsA and could contribute to develop more effective therapies.

Multitrait genome association analysis identifies new susceptibility genes for human anthropometric variation in the GCAT cohort

Background

Heritability estimates have revealed an important contribution of SNP variants for most common traits; however, SNP analysis by single-trait genome-wide association studies (GWAS) has failed to uncover their impact. In this study, we applied a multitrait GWAS approach to discover additional factor of the missing heritability of human anthropometric variation.

Methods

We analysed 205 traits, including diseases identified at baseline in the GCAT cohort (Genomes For Life- Cohort study of the Genomes of Catalonia) (n=4988), a Mediterranean adult population-based cohort study from the south of Europe. We estimated SNP heritability contribution and single-trait GWAS for all traits from 15 million SNP variants. Then, we applied a multitrait-related approach to study genome-wide association to anthropometric measures in a two-stage meta-analysis with the UK Biobank cohort (n=336 107).

Results

Heritability estimates (eg, skin colour, alcohol consumption, smoking habit, body mass index, educational level or height) revealed an important contribution of SNP variants, ranging from 18% to 77%. Single-trait analysis identified 1785 SNPs with genome-wide significance threshold. From these, several previously reported single-trait hits were confirmed in our sample with LINC01432 (p=1.9×10⁻⁹) variants associated with male baldness, LDLR variants with hyperlipidaemia (ICD-9:272) (p=9.4×10⁻¹⁰) and variants in IRF4 (p=2.8×10⁻⁵⁷), SLC45A2 (p=2.2×10⁻¹³⁰), HERC2 (p=2.8×10⁻¹⁷⁶), OCA2 (p=2.4×10⁻¹²¹) and MC1R (p=7.7×10⁻²²) associated with hair, eye and skin colour, freckling, tanning capacity and sun burning sensitivity and the Fitzpatrick phototype score, all highly correlated cross-phenotypes. Multitrait meta-analysis of anthropometric variation validated 27 loci in a two-stage meta-analysis with a large British ancestry cohort, six of which are newly reported here (p value threshold <5×10⁻⁹) at ZRANB2-AS2, PIK3R1, EPHA7, MAD1L1, CACUL1 and MAP3K9.

Conclusion

Considering multiple-related genetic phenotypes improve associated genome signal detection. These results indicate the potential value of data-driven multivariate phenotyping for genetic studies in large population-based cohorts to contribute to knowledge of complex traits.

Genomic profiling in advanced stage non-small-cell lung cancer patients with platinum-based chemotherapy identifies germline variants with prognostic value in SMYD2

OBJECTIVE

The aim of the study was to investigate the relationship between germline variations as a prognosis biomarker in patients with advanced Non-Small-Cell-Lung-Cancer (NSCLC) subjected to first-line platinum-based treatment.

MATERIALS AND METHODS

We carried out a two-stage genome-wide-association study in non-small-cell lung cancer patients with platinum-based chemotherapy in an exploratory sample of 181 NSCLC patients from Caucasian origin, followed by a validation on 356 NSCLC patients from the same ancestry (Valencia, Spain).

RESULTS

We identified germline variants in SMYD2 as a prognostic factor for survival in patients with advanced NSCLC receiving chemotherapy. SMYD2 alleles are associated to a decreased overall survival and with a reduced Time to Progression. In addition, enrichment pathway analysis identified 361 variants in 40 genes to be involved in poorer outcome in advanced-stage NSCLC patients.

CONCLUSION

Germline SMYD2 alleles are associated with bad clinical outcome of first-line platinum-based treatment in advanced NSCLC patients. This result supports the role of SMYD2 in the carcinogenic process, and might be used as prognostic signature directing patient stratification and the choice of therapy.

MICROABSTRACT

A two-Stage Genome wide association study in Caucasian population reveals germline genetic variation in SMYD2 associated to progression disease in first-line platinum-based treatment in advanced NSCLC patients. SMYD2 profiling might have prognostic / predictive value directing choice of therapy and enlighten current knowledge on pathways involved in human carcinogenesis as well in resistance to chemotherapy.

Decreased lipid metabolism but increased FA biosynthesis are coupled with changes in liver microRNAs in obese subjects with NAFLD

BACKGROUND/OBJECTIVE

Many controversies regarding the association of liver miRNAs with obesity and nonalcoholic fatty liver diseases (NAFLD) call for additional validations. This study sought to investigate variations in genes and hepatic miRNAs in a sample of obese patients with or without NAFLD and human hepatocytes (HH).

SUBJECTS/METHODS

A total of 60 non-consecutive obese women following bariatric surgery were recruited. Subjects were classified as NAFLD (n=17), borderline (n=24) and controls (n=19) with normal enzymatic profile, liver histology and ultrasound assessments. Profiling of 744 miRNAs was performed in 8 obese women with no sign of hepatic disease and 11 NAFLD patients. Additional validation and expression of genes related to de novo fatty acid (FA) biosynthesis, uptake, transport and β-oxidation; glucose metabolism, and inflammation was tested in the extended sample. Induction of NAFLD-related genes and miRNAs was examined in HepG2 cells and primary HH treated with palmitic acid (PA), a combination of palmitate and oleic acid, or high glucose, and insulin (HG) mimicking insulin resistance in NAFLD.

RESULTS

In the discovery sample, 14 miRNAs were associated with NAFLD. Analyses in the extended sample confirmed decreased miR-139-5p, miR-30b-5p, miR-122-5p and miR-422a, and increased miR-146b-5p in obese subjects with NAFLD. Multiple linear regression analyses disclosed that NAFLD contributed independently to explain miR-139-5p (P=0.005), miR-30b-5p (P=0.005), miR-122-5p (P=0.021), miR-422a (P=0.007) and miR-146a (P=0.033) expression variance after controlling for confounders. Decreased miR-122-5p in liver was associated with impaired FA usage. Expression of inflammatory and macrophage-related genes was opposite to decreased miR-30b-5p, miR-139-5p and miR-422a, whereas increased miR-146b-5p was associated with FABP4 and decreased glucose metabolism and FA mobilization. In partial agreement, PA (but not HG) led to decreased miR-139-5p, miR-30b-5p, miR-422a and miR-146a in vitro, in parallel with increased lipogenesis and FA transport, decreased glucose metabolism and diminished FA oxidation.

CONCLUSION

This study confirms decreased liver glucose and lipid metabolism but increased FA biosynthesis coupled with changes in five unique miRNAs in obese patients with NAFLD.

miRNAs in cerebrospinal fluid identify patients with MS and specifically those with lipid-specific oligoclonal IgM bands

BACKGROUND

MicroRNAs (miRNAs) are non-coding RNAs that regulate cellular processes by controlling protein translation and mRNA degradation.

OBJECTIVE

We aimed to explore the miRNA signature of multiple sclerosis (MS) patients versus controls and the possibility that patients with lipid-specific oligolconal IgM bands (LS_OCMB), a predictor of a more severe disease course, may have a distinct profile.

METHODS

An extensive profile of 754 miRNAs was evaluated in the cerebrospinal fluid (CSF) of 14 women using TaqMan low-density arrays. Differentially expressed miRNAs together with others previously identified in the literature were validated in an extended sample of 86 MS patients (39 LS_OCMB+) and 55 controls.

RESULTS

We detected higher levels of miR-150 in MS patients and especially in those with LS_OCMB+. Other miRNAs (miR-328, miR-30a-5p and miR-645) were up-regulated in MS patients compared to controls while miR-21, miR-199a-3p, miR-191, miR-365, miR-106a and miR-146a showed down-regulated expression. Considering only patients with LS_OCMB+, we also detected up-regulation of miR-30a-5p, miR-150 and miR-645 and down-regulation of miR-191 compared to controls.

CONCLUSION

Our study confirms the recent findings regarding the deregulated expression of miR-150 not only with MS but also with the presence of LS_OCMB. This study highlights the potential utility of miRNAs in CSF as biomarkers for MS.

Unravelling the hidden DNA structural/physical code provides novel insights on promoter location

Although protein recognition of DNA motifs in promoter regions has been traditionally considered as a critical regulatory element in transcription, the location of promoters, and in particular transcription start sites (TSSs), still remains a challenge. Here we perform a comprehensive analysis of putative core promoter sequences relative to non-annotated predicted TSSs along the human genome, which were defined by distinct DNA physical properties implemented in our ProStar computational algorithm. A representative sampling of predicted regions was subjected to extensive experimental validation and analyses. Interestingly, the vast majority proved to be transcriptionally active despite the lack of specific sequence motifs, indicating that physical signaling is indeed able to detect promoter activity beyond conventional TSS prediction methods. Furthermore, highly active regions displayed typical chromatin features associated to promoters of housekeeping genes. Our results enable to redefine the promoter signatures and analyze the diversity, evolutionary conservation and dynamic regulation of human core promoters at large-scale. Moreover, the present study strongly supports the hypothesis of an ancient regulatory mechanism encoded by the intrinsic physical properties of the DNA that may contribute to the complexity of transcription regulation in the human genome.

Transferrin receptor-1 gene polymorphisms are associated with type 2 diabetes

BACKGROUND

Iron is involved in oxidative stress and type 2 diabetes (T2D). Transferrin receptor (TFRC) constitutes the major receptor by which most cells take up iron. The aim of this study was to evaluate whether TFRC gene polymorphisms are associated with T2D.

MATERIALS AND METHODS

We evaluated TFRC gene polymorphism (rs3817672, 210AG, S142G) in a sample of T2D patients and nondiabetic controls (n = 722), and 39 SNPs within the TFRC genomic region analysed by the Welcome Trust Case Control Consortium (WTCCC) (1921 T2D subjects and 3000 controls). In a subset of subjects, glucose tolerance and insulin sensitivity were also studied.

RESULTS

The frequency of the G allele at the position 210 of the TFRC gene was significantly higher in T2D patients. Both GG and GA genotypes had a 69% (P < 0.01) greater risk of developing T2D estimated under a dominant model. The increased prevalence of the G allele run in parallel to increased sex-adjusted log-serum ferritin and slightly increased soluble transferrin receptor among patients with T2D. Furthermore, post-load glucose and insulin sensitivity were significantly associated with circulating soluble transferrin receptor, and insulin sensitivity was significantly associated with serum ferritin among G allele carriers, (r = -0.33, P = 0.001) but not in AA homozygotes. Sixteen other TFRC SNPs were also associated to T2D according to the Welcome Trust Case Control Consortium data.

CONCLUSION

TFRC gene variants are associated with T2D.

ZNRD1 (zinc ribbon domain-containing 1) is a host cellular factor that influences HIV-1 replication and disease progression

BACKGROUND

Human immunodeficiency virus (HIV) takes advantage of multiple host proteins to support its own replication. The gene ZNRD1 (zinc ribbon domain-containing 1) has been identified as encoding a potential host factor that influenced disease progression in HIV-positive individuals in a genomewide association study and also significantly affected HIV replication in a large-scale in vitro short interfering RNA (siRNA) screen. Genes and polymorphisms identified by large-scale analysis need to be followed up by means of functional assays and resequencing efforts to more precisely map causal genes.

METHODS

Genotyping and ZNRD1 gene resequencing for 208 HIV-positive subjects (119 who experienced long-term nonprogression [LTNP] and 89 who experienced normal disease progression) was done by either TaqMan genotyping assays or direct sequencing. Genetic association analysis was performed with the SNPassoc package and Haploview software. siRNA and short hairpin RNA (shRNA) specifically targeting ZNRD1 were used to transiently or stably down-regulate ZNRD1 expression in both lymphoid and nonlymphoid cells. Cells were infected with X4 and R5 HIV strains, and efficiency of infection was assessed by reporter gene assay or p24 assay.

RESULTS

Genetic association analysis found a strong statistically significant correlation with the LTNP phenotype (single-nucleotide polymorphism rs1048412; P = .0004), independently of HLA-A10 influence. siRNA-based functional analysis showed that ZNRD1 down-regulation by siRNA or shRNA impaired HIV-1 replication at the transcription level in both lymphoid and nonlymphoid cells.

CONCLUSION

Genetic association analysis unequivocally identified ZNRD1 as an independent marker of LTNP to AIDS. Moreover, in vitro experiments pointed to viral transcription as the inhibited step. Thus, our data strongly suggest that ZNRD1 is a host cellular factor that influences HIV-1 replication and disease progression in HIV-positive individuals.

Nucleotide, cytogenetic and expression impact of the human chromosome 8p23.1 inversion polymorphism

Background

The human chromosome 8p23.1 region contains a 3.8–4.5 Mb segment which can be found in different orientations (defined as genomic inversion) among individuals. The identification of single nucleotide polymorphisms (SNPs) tightly linked to the genomic orientation of a given region should be useful to indirectly evaluate the genotypes of large genomic orientations in the individuals.

Results

We have identified 16 SNPs, which are in linkage disequilibrium (LD) with the 8p23.1 inversion as detected by fluorescent in situ hybridization (FISH). The variability of the 8p23.1 orientation in 150 HapMap samples was predicted using this set of SNPs and was verified by FISH in a subset of samples. Four genes (NEIL2, MSRA, CTSB and BLK) were found differentially expressed (p<0.0005) according to the orientation of the 8p23.1 region. Finally, we have found variable levels of mosaicism for the orientation of the 8p23.1 as determined by FISH.

Conclusion

By means of dense SNP genotyping of the region, haplotype-based computational analyses and FISH experiments we could infer and verify the orientation status of alleles in the 8p23.1 region by detecting two short haplotype stretches at both ends of the inverted region, which are likely the relic of the chromosome in which the original inversion occurred. Moreover, an impact of 8p23.1 inversion on gene expression levels cannot be ruled out, since four genes from this region have statistically significant different expression levels depending on the inversion status. FISH results in lymphoblastoid cell lines suggest the presence of mosaicism regarding the 8p23.1 inversion.

Decreased regional brain volume and cognitive impairment in preterm children at low risk

OBJECTIVE

To investigate whether preterm children with low risk for neurodevelopmental deficits show long-term changes in gray matter (GM) and white matter (WM) volumes compared with term children and to relate these changes to cognitive outcome.

METHODS

MRI was used to evaluate 20 preterm children who were determined to be at low risk for neurodevelopmental deficits and were born between 30 and 34 weeks' gestational age without major neonatal morbidity or cerebral pathology in the neonatal period and 22 matched, term control subjects. Volumetric images were analyzed by means of voxel-based morphometry to identify regional cerebral alterations. Children also underwent cognitive and behavioral/emotional assessments.

RESULTS

Preterm children showed global and regional GM volume reductions in several brain areas, including temporal and parietal lobes and concomitant WM volume reductions in the same areas, although only the left temporal regions achieved statistical significance. Global intellectual performance in the preterm group was significantly decreased compared with control subjects. Neither behavioral nor emotional problems were found in the preterm group. In the whole sample, we found a positive correlation between GM volume bilaterally in the middle temporal and in the postcentral gyri with IQ. Positive correlations were observed between GM and gestational age at birth in parietal and temporal cerebral regions and with WM in parietal regions.

CONCLUSION

Preterm birth has an important impact on the neurodevelopmental and cognitive outcome of children at 9 years of age, being a risk factor for decreased regional cortical GM and WM even in preterm children with low risk for neurodevelopmental deficits.

Hypothalamus transcriptome profile suggests an anorexia-cachexia syndrome in the anx/anx mouse model

The anx/anx mouse displays poor appetite and lean appearance and is considered a good model for the study of anorexia nervosa. To identify new genes involved in feeding behavior and body weight regulation we performed an expression profiling in the hypothalamus of the anx/anx mice. Using commercial microarrays we detected 156 differentially expressed genes and validated 92 of those using TaqMan low-density arrays. The expression of a set of 87 candidate genes selected based on literature evidences was also quantified by TaqMan low-density arrays. Our results showed enrichment in deregulated genes involved in cell death, cell morphology, and cancer, as well as an alteration of several signaling circuits involved in energy balance including neuropeptide Y and melanocortin signaling. The expression profile along with the phenotype led us to conclude that anx/anx mice resemble the anorexia-cachexia syndrome typically observed in cancer, infection with human immunodeficiency virus or chronic diseases, rather than starvation, and that anx/anx mice could be considered a good model for the treatment and investigation of this condition.

Proton magnetic resonance spectroscopy reveals medial temporal metabolic abnormalities in adolescents with history of preterm birth

Prematurity is associated with volumetric reductions in specific brain areas such as the hippocampus and with metabolic changes that can be detected by spectroscopy. Short echo time (35 ms) Proton magnetic resonance spectroscopy (1H MRS) was performed to assess possible medial temporal lobe metabolic abnormalities in 21 adolescents with preterm birth (mean age: 14.8, SD: 1.3) compared with an age-matched control sample (mean age: 14.8, SD: 1.6). 1H MRS spectra were analyzed with linear combination model fitting, obtaining the absolute metabolite concentrations for Creatine (Cr), and myo-inositol (Ins). In addition, the following metabolite sums were measured: total Cho (glycerophospho-choline + phosphocholine), total N-acetyl-aspartate + N-acetyl-aspartylglutamate (NA), and total Glx (glutamate + glutamine). A stereological analysis was performed to calculate hippocampal volume. Absolute Cr, and total NA values were decreased in the preterm group (p = 0.016; p = 0.002, respectively). The preterm also showed a hippocampal reduction (p < 0.0001). Significant relationships were found between gestational age and different metabolites and the hippocampal volume. Moreover, hippocampal volume correlated with brain metabolites in the whole sample. Results demonstrate that prematurity affects medial temporal lobe metabolites, and that the alteration is related to structural changes, suggesting that the cerebral changes persist until adolescence.

Association of NTRK3 and its interaction with NGF suggest an altered cross-regulation of the neurotrophin signaling pathway in eating disorders

Eating disorders (EDs) are complex psychiatric diseases that include anorexia nervosa and bulimia nervosa, and have higher than 50% heritability. Previous studies have found association of BDNF and NTRK2 to ED, while animal models suggest that other neurotrophin genes might also be involved in eating behavior. We have performed a family-based association study with 151 TagSNPs covering 10 neurotrophin signaling genes: NGFB, BDNF, NTRK1, NGFR/p75, NTF4/5, NTRK2, NTF3, NTRK3, CNTF and CNTFR in 371 ED trios of Spanish, French and German origin. Besides several nominal associations, we found a strong significant association after correcting for multiple testing (P = 1.04 x 10(-4)) between ED and rs7180942, located in the NTRK3 gene, which followed an overdominant model of inheritance. Interestingly, HapMap unrelated individuals carrying the rs7180942 risk genotypes for ED showed higher levels of expression of NTRK3 in lymphoblastoid cell lines. Furthermore, higher expression of the orthologous murine Ntrk3 gene was also detected in the hypothalamus of the anx/anx mouse model of anorexia. Finally, variants in NGFB gene appear to modify the risk conferred by the NTRK3 rs7180942 risk genotypes (P = 4.0 x 10(-5)) showing a synergistic epistatic interaction. The reported data, in addition to the previous reported findings for BDNF and NTRK2, point neurotrophin signaling genes as key regulators of eating behavior and their altered cross-regulation as susceptibility factors for EDs.

MRPS18CP2 alleles and DEFA3 absence as putative chromosome 8p23.1 modifiers of hearing loss due to mtDNA mutation A1555G in the 12S rRNA gene

Background

Mitochondrial DNA (mtDNA) mutations account for at least 5% of cases of postlingual, nonsyndromic hearing impairment. Among them, mutation A1555G is frequently found associated with aminoglycoside-induced and/or nonsyndromic hearing loss in families presenting with extremely variable clinical phenotypes. Biochemical and genetic data have suggested that nuclear background is the main factor involved in modulating the phenotypic expression of mutation A1555G. However, although a major nuclear modifying locus was located on chromosome 8p23.1 and regardless intensive screening of the region, the gene involved has not been identified.

Methods

With the aim to gain insights into the factors that determine the phenotypic expression of A1555G mutation, we have analysed in detail different genetic and genomic elements on 8p23.1 region (DEFA3 gene absence, CLDN23 gene and MRPS18CP2 pseudogene) in a group of 213 A1555G carriers.

Results

Family based association studies identified a positive association for a polymorphism on MRPS18CP2 and an overrepresentation of DEFA3 gene absence in the deaf group of A1555G carriers.

Conclusion

Although none of the factors analysed seem to have a major contribution to the phenotype, our findings provide further evidences of the involvement of 8p23.1 region as a modifying locus for A1555G 12S rRNA gene mutation.

Altered brain-derived neurotrophic factor blood levels and gene variability are associated with anorexia and bulimia

Murine models and association studies in eating disorder (ED) patients have shown a role for the brain-derived neurotrophic factor (BDNF) in eating behavior. Some studies have shown association of BDNF -270C/T single-nucleotide polymorphism (SNP) with bulimia nervosa (BN), while BDNF Val66Met variant has been shown to be associated with both BN and anorexia nervosa (AN). To further test the role of this neurotrophin in humans, we screened 36 SNPs in the BDNF gene and tested for their association with ED and plasma BDNF levels as a quantitative trait. We performed a family-based association study in 106 ED nuclear families and analyzed BDNF blood levels in 110 ED patients and in 50 sib pairs discordant for ED. The rs7124442T/rs11030102C/rs11030119G haplotype was found associated with high BDNF levels (mean BDNF TCG haplotype carriers = 43.6 ng/ml vs. mean others 23.0 ng/ml, P = 0.016) and BN (Z = 2.64; P recessive = 0.008), and the rs7934165A/270T haplotype was associated with AN (Z =-2.64; P additive = 0.008). The comparison of BDNF levels in 50 ED discordant sib pairs showed elevated plasma BDNF levels for the ED group (mean controls = 41.0 vs. mean ED = 52.7; P = 0.004). Our data strongly suggest that altered BDNF levels modulated by BDNF gene variability are associated with the susceptibility to ED, providing physiological evidence that BDNF plays a role in the development of AN and BN, and strongly arguing for its involvement in eating behavior and body weight regulation.

Increased cerebral activity in Parkinson?s disease patients carrying the DRD2 TaqIA A1 allele during a demanding motor task: a compensatory mechanism?

Previous studies suggest that neuroimaging techniques are useful for detecting the effects of functional genetic polymorphisms on brain function in healthy subjects or in patients presenting with psychiatric or neurodegenerative conditions. Former evidence showed that individuals carrying risk alleles displayed broader patterns of brain activity during behavioural and cognitive tasks, despite being clinically comparable to non-carriers. This suggests the presence of compensatory brain mechanisms. In the present study, we investigated this effect in Parkinson's disease (PD) patients carrying the DRD2 TaqIA A1 allelic variant. This variant may confer an increased risk of developing the disease and/or influence the clinical presentation. During a complex sequential motor task, we evidenced by functional magnetic resonance imaging that A1 allele carriers activated a larger network of bilateral cerebral areas than non-carriers, including cerebellar and premotor regions. Both groups had similar clinical and demographic measures. In addition, their motor performance during the functional magnetic resonance experiment was comparable. Therefore, our conclusions, pending replication in a larger sample, seem to reflect the recruitment of compensatory cerebral resources during motor processing in PD patients carrying the A1 allele.

Abnormal orbitofrontal development due to prematurity

OBJECTIVE

To investigate the effects of prematurity on sulcal formation.

METHODS

We evaluated the depth and volume of the primary olfactory sulcus (developed at 16 weeks' gestation) and the secondary orbital sulci (which start to develop at 28 weeks' gestation) in a sample of 22 adolescents with history of very-preterm birth (VPTB). We compared this preterm sample with a sample of subjects born at term and matched by age, gender, and sociocultural status. The Anatomist/BrainVISA 3.0.1 package was used to identify and quantify the sulci. In addition, voxel-based morphometry (VBM) was used to analyze possible reductions of gray and white matter in the orbitofrontal area.

RESULTS

Compared with controls, we found a significant reduction in the secondary sulci depth but not in the primary sulcus in the VPTB. VBM analysis showed reduced gray-matter volume in VPTB in the orbital region.

CONCLUSIONS

Premature birth affects cerebral gyrification, and this impairment is not reversible during childhood. Identification of the specific factors involved in abnormal brain maturation may lead to effective interventions.

MR imaging of temporomandibular joint dysfunction: a pictorial review

Temporomandibular joint (TMJ) dysfunction is a common condition that is best evaluated with magnetic resonance (MR) imaging. The first step in MR imaging of the TMJ is to evaluate the articular disk, or meniscus, in terms of its morphologic features and its location relative to the condyle in both closed- and open-mouth positions. Disk location is of prime importance because the presence of a displaced disk is a critical sign of TMJ dysfunction. However, disk displacement is also frequently seen in asymptomatic volunteers, so that other findings may be required to help make the diagnosis. These findings include thickening of an attachment of the lateral pterygoid muscle, rupture of retrodiskal layers, and joint effusion and can serve as indirect early signs of TMJ dysfunction. It is important for the radiologist to detect early MR imaging signs of dysfunction, thereby avoiding the evolution of this condition to its final stage, an advanced and irreversible phase that is characterized by osteoarthritic changes such as condylar flattening or osteophytes. Further studies conducted with the latest MR imaging techniques will allow a better understanding of the sources of TMJ pain and of any discrepancy between imaging findings and patient symptoms.

White matter volume and concentration reductions in adolescents with history of very preterm birth: a voxel-based morphometry study

Very preterm birth (VPTB) is an important risk factor for white matter (WM) damage. We used voxel-based morphometry (VBM) to examine regional WM brain abnormalities in 50 adolescents with antecedents of very preterm birth (VPTB) without evidence of WM damage on T2-weighted MRI. This group was compared with a group of 50 subjects born at term and matched for age, handedness and socio-cultural status. We also examined the relationship between WM changes and gestational age (GA) and weight (GW) at birth in VPTB subjects. Both modulated and unmodulated VBM analyses showed significant abnormalities in several WM brain regions in the VPTB group, involving all the cerebral lobes. However, density analyses (unmodulated data) mainly identified periventricular damage and the involvement of the longitudinal fascicles while volume analyses (modulated data) detected WM decreases in regions distant from the ventricular system, located at the origin and end of the long fascicles. A significant correlation was found between WM decreases and both GA and GW in various brain regions: the lower the GA and GW, the lower the WM integrity. This study supports the current view that widespread white matter impairment is associated with immature birth.

Correlations of thalamic reductions with verbal fluency impairment in those born prematurely

Prematurity is associated with reduced brain volume, and the thalamus is among the structures most affected. We used a voxel-based morphometry analysis of gray matter to map regional atrophy in the thalamus in a sample of 30 adolescents with antecedents of very preterm birth. The preterm sample was compared with 30 controls matched by age, sex, handedness and sociocultural status. Individuals with very preterm birth differed from controls in several thalamic nuclei, and semantic and phonetic fluency showed different correlation patterns with brain volume. Semantic fluency achieved significant correlations with more thalamic nuclei than phonetic fluency. These results agree with functional magnetic resonance imaging studies showing that semantic fluency involves more cerebral regions than phonetic fluency.

Hippocampal functional magnetic resonance imaging during a face-name learning task in adolescents with antecedents of prematurity

Functional magnetic resonance imaging (fMRI) was used to map hippocampal activation during a declarative memory task in a sample of 14 adolescents with antecedents of prematurity (AP). The sample with AP was matched by age, sex and handedness with 14 full-term controls with no history of neurological or psychiatric illness. The target task consisted in learning 16 novel face-name pairs, and the control task involved the examination of two repeated face-name pairs. Stereological methods were also used to quantify hippocampal volumes. In both groups, we observed increased activation in the learning condition compared to the control task in the right fusiform gyrus and the left inferior occipital gyrus, but only premature subjects activated the hippocampus. Group comparison of the activation versus control conditions showed that prematures had greater activity in the right hippocampus than controls during the encoding of the word-face association. Volumetric analyses showed a significant left hippocampal volume loss in adolescents with AP. In addition, we found a significant positive correlation in the premature group between right hippocampal activation and face-name recognition. Functional MRI data also correlated with structural MRI data: right hippocampal activation correlated positively with right hippocampal volume. Our findings are consistent with previous studies of brain plasticity after focal lesions. Left hippocampal tissue loss may be related to an increase in contralateral brain activity, probably reflecting a compensatory mechanism. Our data also suggest that this plasticity is not enough to achieve normal performance.

Cerebral correlates of declarative memory dysfunctions in early traumatic brain injury

We investigated residual brain damage in subjects who suffered severe traumatic brain injury (TBI) in childhood, and its relationship with declarative memory impairment. Magnetic resonance imaging (MRI) volumetric data and memory performance were compared between 16 adolescents with antecedents of severe TBI and 16 matched normal controls. Volumes of grey matter, white matter, cerebrospinal fluid (CSF), hippocampus, and caudate nuclei were measured. Verbal memory was assessed by the Rey's Auditory Verbal Learning test and visual memory by the Rey's Complex Figure. TBI patients performed significantly worse than controls in both verbal and visual memory. Patients presented decreased white matter volume and increased CSF. The hippocampus was reduced, but not the caudate nuclei. Memory performance correlated with CSF. Plasticity is incomplete for structural and functional deficits in children with TBI. Hippocampal atrophy, white matter loss, and memory impairment remain until adolescence. Memory sequelae are related more to diffuse brain injury, as reflected by MRI findings of increased CSF, than to hippocampal injury.

Magnetic resonance abnormalities associated with cognitive dysfunction in primary Sjögren Syndrome

OBJECTIVE

The aim of the present study was to examine the relationship between magnetic resonance imaging (MRI) findings and cognitive functioning in a group of patients with primary Sjögren Syndrome (SS).

METHODS

Fifteen subjects with primary SS and fifteen control subjects diagnosed with migraine were assessed. All subjects received a detailed neuropsychological assessment especially sensitive to fronto-subcortical disorders and a MRI study. Volumetric measures of the ventricular system and intracranial volume and measures of the severity and distribution of signal hyperintensities were obtained.

RESULTS

Patients with SS showed larger ventricular volume than control subjects with migraine. The severity of MRI signal hyperintensities and ventricular volume were related to several cognitive and psychiatric variables.

CONCLUSION

Patients with primary SS have morphological abnormalities that are related to neuropsychological and psychiatric disturbances. These findings provide some support for the organic etiology of cognitive and psychiatric dysfunction and thus for central nervous system involvement in SS.

Basal ganglia N-acetylaspartate correlates with the performance in the procedural task 'Tower of Hanoi' of neuroleptic-naive schizophrenic patients

We tested the hypothesis that basal ganglia dysfunction may be related to procedural learning impairment in schizophrenia. We determined the N-acetylaspartate/choline (NAA/Cho) ratio in the left striatal area in 11 young first-episode antipsychotic-naive patients and matched controls. Procedural learning was assessed by the four-disk version of the Tower of Hanoi. Analysis of variance showed that the number of moves and the execution time had a significant group effect (P=0.02, P<0.0001, respectively). Correlation analysis between procedural learning and the NAA/Cho ratio showed a negative significant correlation only in patients, measured by both time (P=0.006) and by moves (P=0.001). In summary, we found that schizophrenic patients have impaired procedural learning, and that this impairment is related to basal ganglia metabolism.

Apolipoproteins E and C1 and brain morphology in memory impaired elders

Previous research has shown that polymorphisms of the apolipoproteins E ( APOE) and APOC1 represent genetic risk factors for dementia and for cognitive impairment in the elderly. The brain mechanisms by which these genetic variations affect behavior or clinical severity are poorly understood. We studied the effect of APOE and APOC1 genes on magnetic resonance imaging measures in a sample of 50 subjects with age-associated memory impairment. The APOE E4 allele was associated with reduced left hippocampal volumes and APOE*E3 status was associated with greater frontal lobe white matter volumes. However, no APOE effects were observed when analyses accounted for other potential confounding variables. The effects of APOC1 on hippocampal volumes appeared to be more robust than those of the APOE polymorphism. However, no modulatory effects on brain morphology outside the medial temporal lobe region were observed when demographic variables, clinical status, and other anatomical brain measurements were taken into consideration. Our results suggest that the role of the APOC1 polymorphism in brain morphology of the cognitively impaired elderly should be examined in further studies.

Residual hippocampal atrophy in asphyxiated term neonates

BACKGROUND AND PURPOSE

Previous studies have shown the hippocampus and basal ganglia to be highly sensitive to hypoxic-ischemic insult. The authors' aim was to evaluate the long-term effects of perinatal asphyxia (PA) on the hippocampus and caudate nucleus in a group of participants born at term and who met the criteria for hypoxic-ischemic encephalopathy (HIE). Additionally, the authors looked for damage in other brain regions using voxel-based morphometry (VBM).

METHODS

The sample consisted of 13 participants (8 boys and 5 girls) with a mean age at study of 16.23 years (+/- 2.89) with antecedents of perinatal asphyxia, diagnosed as moderate hypoxic-ischemic encephalopathy. A group of 13 healthy adolescents matched for age, sex, educational level, and social background were recruited as a comparison group. MR scans were acquired on a 1.5T Signa (General Electric, Milwaukee, WI) to evaluate hippocampal and caudate volumes and to perform VBM analysis. Finally, Rey's Auditory Verbal Learning Test was administered to evaluate verbal long-term memory.

RESULTS

HIE participants were found to have bilateral hippocampal atrophy (P = .015) and gray matter damage in temporal and frontal lobes. The caudate nucleus showed no atrophic changes in PA participants, and VBM analysis did not reveal other consistent brain abnormalities. Verbal long-term memory was slightly worse in HIE participants.

CONCLUSIONS

These findings indicate that PA produces hippocampal and other nonspecific long-term damage, which cannot be compensated for by plasticity mechanisms. However, this damage does not preclude normal development and scholarship.

(1)H-MR spectroscopy is sensitive to subtle effects of perinatal asphyxia

The authors performed neuropsychological and (1)H-MRS studies in 18 subclinical patients with antecedents of perinatal asphyxia (PA) and in 18 matched control subjects. Patients with PA showed reduced values of N-acetylaspartate (NAA) in both the basal ganglia and the midtemporal region (MTR) and reduced NAA/choline values in the MTR. Neuropsychological testing showed group differences in tasks related to attention and memory. These results indicate persistent dysfunctions in cerebral structures vulnerable to hypoxia and demonstrate the utility of MRS for the long-term evaluation of cerebral sequelae of neonatal asphyxia.

MRI and genetic correlates of cognitive function in elders with memory impairment

The present study investigated the relationship between genetic variation, MRI measurements and neuropsychological function in a sample of 58 elders exhibiting memory decline. In agreement with previous reports, we found that the epsilon4 allele of the apolipoprotein E (APOE) and the D allele of the angiotensin converting enzyme (ACE) polymorphisms negatively modulated the cognitive performance. Further, we found an association between the A allele of the apolipoprotein C1 (APOC1) polymorphism and poorer memory and frontal lobe function. No clear associations emerged between MRI measures of white matter lesions (WML) or hippocampal sulcal cavities (HSC) and the cognitive performance after controlling for age effects. Further, the degree of WML or HSC lesions was in general not predisposed genetically except for the presence of the A allele of the APOC1 polymorphism that was related to a higher severity of HSC scores. Our results suggest that WML or HSC do not represent important brain correlates of genetic influences on cognitive performance in memory impaired subjects.

[Study of the long term sequelae of traumatic brain injury: evaluation of declarative and procedural memory, and its neuroanatomic substrate]

INTRODUCTION AND OBJECTIVES

The hippocampus and the striatum have been proposed as respectively cerebral substrates of declarative and procedural memory. Both structures are vulnerable to traumatic brain injury. Although declarative and procedural memory have been reported to be impaired in traumatic brain injury (TBI), volumetric measures have so far failed to associate this impairment with atrophy of hippocampal and striatal structures. In our study, we investigated the profile of declarative and procedural memory in children who suffered from moderate to severe traumatic brain injury during childhood (injury test interval: 9.42+/-1.98 years).

PATIENTS AND METHODS

Nineteen patients and matched controls were evaluated on tests of declarative memory and motor learning. Results showed that TBI subjects exhibit poorer performance in both tasks. Moreover, structural magnetic resonance images were obtained from TBI subjects. In order to relate neuropsychological performance with hippocampal and neostriatal volumetric data, correlation analyses were performed.

RESULTS

Significant positive correlations were obtained between hippocampal volume and memory for objects. Striatal volume correlated positively with motor learning and with verbal memory.

CONCLUSIONS

It thus seems that plasticity does not completely compensate for the memory deficits resultant from neural loss in the immature brain.

Correlation of atrophy measures on MRI with neuropsychological sequelae in children and adolescents with traumatic brain injury

To examine the relationship between neuropsychological sequelae and atrophy parameters from magnetic resonance imaging (MRI) following paediatric moderate-to-severe traumatic brain injury (TBI), 19 head injured children and adolescents were studied at least 6 years after injury. Three-dimensional MRI scans were obtained. A semi-automatic computerized method was used to estimate ventricular volumes and the corpus callosum area. Tests of intellectual, memory, visuospatial, frontal lobe, and motor speed functioning were administered to all patients and to 19 matched normal control subjects. Patients' performance significantly differed from controls in general intellectual function, visual memory, visuospatial and frontal lobe tests. The corpus callosum area correlated strongly with several measures involving processing speed and visuospatial function. Ventricular enlargement was less related to neuropsychological outcome. In conclusion, quantitative measurement of the corpus callosum on MRI reflects neuropsychological outcome better than ventricular dilation in paediatric patients.

MRI atrophy parameters related to cognitive and motor impairment in Parkinson's disease

BACKGROUND

Patients with Parkinson's disease (PD) show specific neuropsychological deficits in attention, memory, visuospatial or frontal lobe functions, which can arise from degeneration of different cerebral structures.

OBJECTIVE

The aim of the present study was to analyze the role of focal degeneration (basal ganglia and substantia nigra) and diffuse cerebral atrophy (ventricular enlargement) in motor/cognitive impairment in PD.

PATIENTS AND METHODS

We administered to 14 patients with advanced PD the following tests: Purdue Pegboard, Rey's Auditory-Verbal Learning test (RAVLT), Benton's Line Orientation, Trail Making, phonemic verbal fluency and Stroop test. Ventricular system, caudate and putamen nuclei and pars compacta of the substantia nigra were quantitatively measured by magnetic resonance imaging. Correlation analyses were carried out.

RESULTS

The results showed that ventricular enlargement is negatively correlated with the performance on RAVLT and Stroop test. No relationship was found between caudate atrophy and cognitive deficits. Degeneration of putamen nucleus was found to be associated with motor deficits.

CONCLUSION

Memory and frontal impairment are related to diffuse cerebral degeneration and the motor deficit is related to degeneration of the putamen nucleus.

Neuroradiological and clinical findings in rhombencephalosynapsis

Rhombencephalosynapsis is an unusual disorder characterised by maldevelopment of the rhombencephalon, sometimes with supratentorial midline anomalies. We report MRI findings in a 39-year-old woman, the oldest in the literature. MRI demonstrated hypoplasia of the cerebellar vermis, with fusion of the cerebellar hemispheres and abnormally oriented folia. Supratentorial anomalies were also seen.

Cortical laminar necrosis caused by immunosuppressive therapy and chemotherapy

We report three patients in whom neurologic symptoms and cortical laminar necrosis developed after immunosuppressive treatment (cyclosporin A and FK 506) and polychemotherapy (vincristine and methotrexate). Initial neuroradiologic studies showed cortical and white matter involvement. Follow-up studies showed cortical hyper-intense lesions on T1-weighted MR images, consistent with cortical laminar necrosis. The clinical and radiologic data indicate that a transient hypoxic-ischemic process could have been responsible for the encephalic lesions in these three patients.

[Application of magnetic resonance spectroscopy in the study of brain disease]

INTRODUCTION AND OBJECTIVE

Magnetic resonance spectroscopy (MRS) is a non-invasive technique used for the neurochemical study of the brain in vivo. The aim of this work is to review the main investigations that have focused on the study of cerebral pathology.

DEVELOPMENT

Cerebral MRS studies started in 1983 but the maximum development has been in the 90's. The pathologies more investigated were Alzheimer's disease, multiple sclerosis, schizophrenia, and depression. Although several nuclei can be observed the most investigated are phosphor (P31) and hydrogen (H1). Nowadays proton MRS is the more frequently used technique. The low levels of N-acetyl-aspartate are a good indicator of neuronal loss. Their determination is complementary to the volumetric structural studies from magnetic resonance imaging. The peak of myo-inositol seems to be a neurochemical marker for the Alzheimer's disease.

CONCLUSIONS

MRS have contributed to the increase of knowledge about the physiopathology of normal aging, degenerative processes, demyelinating and psychiatric diseases. Potentially can contribute to differential diagnose in Alzheimer's and Parkinson's diseases. Recently it has also been opened a new research potential in the field of the pharmacological treatment effects in discrete cerebral regions.

Cognitive and behavioral changes after unilateral posteroventral pallidotomy: relationship with lesional data from MRI

We investigated cognitive and behavioral changes after unilateral posteroventral pallidotomy, and their relationship with lesion size and location as identified in magnetic resonance image quantitative analysis. Fifteen consecutive patients with Parkinson's disease were assessed neuropsychologically before and after unilateral posteroventral pallidotomy (five right and 10 left). Immediate postsurgery evaluation (1 week) demonstrated significant worsening of memory, motor learning, motor speed, and verbal fluency. In the 3-month follow up, learning, memory, and speed returned to the presurgical level, but verbal fluency remained below the baseline. Significant improvements were observed in visuospatial functions and obsessive-compulsive behavior. Lesional volume did not correlate with neuropsychologic changes. Left lesions produced more impairment in verbal fluency than right-sided lesions. Regression analysis identified two lesional areas in the pallidum mediale internum. These regions accounted for 68% of the variance in the visuospatial changes.

Magnetic resonance imaging in myelofibrosis and essential thrombocythaemia: contribution to differential diagnosis

To ascertain the value of magnetic resonance (MR) imaging in the differential diagnosis between myelofibrosis (MF) and essential thrombocythaemia (ET), 38 patients were analysed. 20 patients had MF (idiopathic myelofibrosis, 15 cases; post-ET myelofibrosis, four cases; post-polycythaemic MF, one case) and 18 ET. Mean age was 61.5 years (range 30-89) for patients with MF and 60.9 years (range 26-83) for ET patients. MR imaging was performed in the dorsal vertebrae in all cases, and also in both femurs in 2 5 of the patients. In most ET cases the MR signal of the dorsal vertebrae was not modified, whereas it was markedly reduced in MF (P=0.0000001). With regard to femoral marrow, it was usually fatty in ET, with an absent to moderate degree of reconversion seen in the 14 cases analysed, contrasting with the marked degree of reconversion noted in 10/11 patients with MF (P=0.000007). An inverse correlation was demonstrated between the vertebral signal and the degree of femoral reconversion. These differences were due to the fact that in ET the bone marrow adipose tissue is grossly preserved, whereas in MF it is usually markedly decreased or absent. The above results indicate that MR imaging is a useful tool for the differential diagnosis of ET and MF, with the usefulness of this technique increasing when vertebral and femoral bone marrow studies are combined.

[Contribution of magnetic resonance to the differential diagnosis of a collapsed vertebra in a patient with multiple myeloma]

The only safe method to determine whether or not patients diagnosed of smoldering myeloma will progress to symptomatic multiple myeloma (MM) is periodic follow-up. In the last years, several studies have emphasized the efficacy of magnetic resonance imaging (MRI) to detect bone marrow involvement in these patients. However, the detection of a focal spinal lesion in elderly patients raises a diagnostic problem, sometimes difficult to solve, between a benign or malignant origin. We present the case of an elderly women with marked osteoporosis and smoldering myeloma who suddenly complained of pain in dorsal spine. MRI showed focal lesions in two dorsal vertebra consistent with myeloma involvement. However, there were no other signs of progression, the lesions were considered secondary to osteoporosis and calcitonin was administered. This resulted in the disappearance of the pain and the MRI abnormalities, which confirmed its benign etiology. The role and limitations of MRI to detect bone marrow involvement by MM in the evaluation of these patients is reviewed.

Hepatoerythropoietic porphyria: neuroimaging findings

CT and MR findings in two patients with hepatoerythropoietic porphyria are presented. CT scans showed atrophy and cortical mineralization at the same level. MR examination performed in one of the two patients showed mainly frontal cortical atrophy and punctate bright signal on T1- and T2-weighted sequences.

Estimation of bone marrow cellularity by means of vertebral magnetic resonance

BACKGROUND AND OBJECTIVE

A magnetic resonance (MR) signal shows an inverse correlation with bone marrow cellularity. In this study, we investigated the possibility of estimating the degree of bone marrow cellularity by means of this non-invasive technique.

METHODS

In 25 patients with different hematological disorders and homogeneous bone marrow distribution, the percentage of bone marrow cellularity was compared to the MR signal of four middorsal vertebrae in T1 sequence. As internal control, the MR signal of the mid-dorsal spinal cord region was used. The results were expressed as the MR signal ratio (great mean MR signal of four vertebrae/MR signal of the spinal cord).

RESULTS

The correlation coefficient (r) between both parameters was -0.93 (p < 0.0001). All observed values fell within the 90% limits of predicted values. The mean difference between observed and predicted bone marrow cellularity was 5.6 (SD 4.0)%.

INTERPRETATION AND CONCLUSIONS

The measurement of the MR signal is not easy to standardize since it depends to a large degree on the control employed. The spinal cord proved to be a satisfactory internal control of the MR signal. Within defined conditions, MR can be useful for a rough estimate of bone marrow cellularity in several clinical situations, such as analysis of tumor burden for prognosis of some leukemias and the evaluation of response to therapy in both proliferative and hypoplastic disorders.

The "target sign": is it a specific sign of CNS tuberculoma?

In brain lesions, the target sign has been defined as a central nidus of calcification or central enhancement surrounded by a ring of enhancement. It has been considered a pathognomonic finding of central nervous system (CNS) tuberculoma. The purpose of this report is to demonstrate that the target sign related to central enhancement is a nonspecific finding and may lead to erroneous diagnosis of CNS tuberculoma.

[Occult involvement of bone marrow in Hodgkin's disease: detection with magnetic resonance]

Although bone marrow biopsy is considered the best procedure to detect bone marrow involvement by Hodgkin's disease (HD), in recent years several studies have emphasized the value of magnetic resonance imaging (MRI). We present the case of a patient with HD apparently localized in a laterocervical lymph node, who also referred disestasiae at a region corresponding to D10 metamera. Bone marrow biopsy, vertebral TC and 67-Ga scintigraphy were all normal. However, a node of 1 cm in diameter was detected by MRI in the tenth dorsal vertebra. Because of the topographic coincidence between the patient's symptomatology and the MRI findings, the HD was considered to be in advanced stage and CMOPP/ABV chemotherapy was administered, this resulting in a rapid improvement of symptoms and disappearance of the MRI abnormalities. Since in the present case, the MRI determined a change in disease stage and treatment, the role of MRI as a complementary exploration of bone marrow biopsy to detect marrow involvement by HD is reviewed.

[Magnetic resonance of the spinal cord: a densitometric analysis]

BACKGROUND

Images obtained by magnetic resonance can present changes in a variety of haematologic disorders. The vertebral magnetic resonance signal depends chiefly on the relationship between fatty and cellular components of the haemopoietic bone marrow. A quantitative analysis of signal can be performed either during the magnetic resonance examination or on the computer-stored images. In this work, a densitometric grey-scale method is presented allowing to analyze the signal intensity on printed magnetic resonance images for those cases in which the computer-stored information is lacking.

PATIENTS AND METHODS

A comparative study between magnetic resonance signal and the result of the densitometric analysis was carried out in 29 patients with different haematologic disorders. In order to achieve a suitable standardization, an internal control in both measures was used, i.e., the magnetic resonance signal intensity and the grey intensity of an area of spinal cord, respectively, yielding two ratios: magnetic resonance ratio and grey ratio.

RESULTS

The precision analysis of the densitometric method gave the following results: within-batch coefficient of variation was 1.78%, between-batch coefficient of variation was 1.94% and overall reproducibility 6.4%. The correlation between magnetic resonance ratio and grey ratio was very high, i.e., 0.98 (p < 0.001). Moreover, the regression line displayed on ideal location since it originated in the point 0 and showed a slope of 45 degrees.

CONCLUSION

The densitometric method presented in this paper can be useful for the quantitative analysis of the magnetic resonance signal intensity generated by the haemopoietic bone marrow, for those cases in which the computer-stored information is lacking.

[Vertebral hemangioma and quiescent myeloma: association of therapeutic significance]

Smouldering myeloma is a monoclonal gammopathy in which the M component is higher than 30 g/l and the proportion of plasma cells in the bone marrow is higher than 10% with no anemia, renal failure, hypercalcemia, osteolysis or other features due to the monoclonal gammopathy. The recognition of this clinical variant of myeloma resides in the fact that treatment should be deferred until there are clinical or biologic data indicating evident disease progression. Vertebral hemangioma is a relatively frequent benign tumor in the general population which, although usually asymptomatic, may cause local or radicular bone pain. A patient who fulfilled the criteria of myeloma and who complained of localized bone pain in the spinal column is herein presented. Following a study of the dorsolumbar column by computerized tomography and magnetic resonance, bone lesions with radiologic images characteristic of vertebral hemangioma, clearly different from those observed in myelomatous lesions, were identified. This finding conditioned the treatment, which included radiotherapy for the vertebral hemangioma and no treatment for the smouldering myeloma.