Argentinian clinical genomics in a leukodystrophies and genetic leukoencephalopathies cohort: Diagnostic yield in our first 9 years.

INTRODUCTION AND OBJECTIVES: Leukodystrophies and genetic leukoencephalopathies constitute a vast group of pathologies of the cerebral white matter. The large number of etiopathogenic genes and the frequent unspecificity on the clinical-radiological presentation generate remarkable difficulties in the diagnosis approach. Despite recent and significant developments, molecular diagnostic yield is still less than 50%. Our objective was to develop and explore the usefulness of a new diagnostic procedure using standardized molecular diagnostic tools, and next-generation sequencing techniques. MATERIALS AND METHODS: A prospective, observational, analytical study was conducted in a cohort of 46 patients, evaluated between May 2008 and December 2016, with a suspected genetic leukoencephalopathy or leukodystrophy. A diagnostic procedure was set up using classical monogenic tools in patients with characteristic phenotypes, and next-generation techniques in nonspecific ones. RESULTS: Global diagnostic procedure yield was 57.9%, identifying the etiological pathogenesis in 22 of the 38 studied subjects. Analysis by subgroups, Sanger method, and next-generation sequencing showed a yield of 64%, and 46.1% respectively. The most common pathologies were adrenoleukodystrophy, cerebral autosomal-dominant arteriopathy with subcortical infarcts (CADASIL), and vanishing white matter disease. CONCLUSIONS: Our results confirm the usefulness of the proposed diagnostic procedure expressed in a high diagnostic yield and suggest a more optimal cost-effectiveness in an etiological analysis phase.

Neurodevelopmental Outcomes in Preterm Infants with White Matter Injury Using a New MRI Classification.

OBJECTIVE: The aim of this study was to evaluate whether a new MRI scoring system for preterm non-haemorrhagic white matter injury (WMI), derived from the analysis of the natural evolution of WMI throughout the neonatal period until term-equivalent age, can be used for outcome prediction. METHODS: Eighty-two infants <36 weeks gestation with WMI diagnosed from sequential cranial ultrasound and confirmed on neonatal MRI were retrospectively included. WMI was classified in four grades of severity. Neurodevelopmental data at a median age of 24 months were analysed. RESULTS: In 74 surviving children WMI severity was strongly associated with the presence and severity of cerebral palsy (CP) and other neurodevelopmental impairments (Spearman's rank correlation 0.88, p < 0.001). Only 3 children with grade I WMI (9%) developed CP (all ambulant) and their developmental scores were not different to those from the controls, although they started walking significantly later (p = 0.036). Of the 6 children with grade II, 83% developed CP (mild in most), whereas 91% of the 34 children with grade III had CP (moderate-severe in 76%) and all had some degree of neurodevelopmental impairment. Three children with grade III WMI did not develop CP; their imaging showed, in contrast to children who developed CP, that the cysts did not affect the corticospinal tracts; also, myelin in the posterior limb of the internal capsule appeared normal in 2 children and suboptimal in 1. CONCLUSIONS: This MRI scoring system for preterm WMI can be used to predict neurodevelopmental outcomes. Individualized assessment of the site of lesions and the progression of myelination improves prognostic accuracy.

Case definition and classification of leukodystrophies and leukoencephalopathies.

OBJECTIVE: An approved definition of the term leukodystrophy does not currently exist. The lack of a precise case definition hampers efforts to study the epidemiology and the relevance of genetic white matter disorders to public health. METHOD: Thirteen experts at multiple institutions participated in iterative consensus building surveys to achieve definition and classification of disorders as leukodystrophies using a modified Delphi approach. RESULTS: A case definition for the leukodystrophies was achieved, and a total of 30 disorders were classified under this definition. In addition, a separate set of disorders with heritable white matter abnormalities but not meeting criteria for leukodystrophy, due to presumed primary neuronal involvement and prominent systemic manifestations, was classified as genetic leukoencephalopathies (gLE). INTERPRETATION: A case definition of leukodystrophies and classification of heritable white matter disorders will permit more detailed epidemiologic studies of these disorders.

Update on several/certain adult-onset genetic leukoencephalopathies: clinical signs and molecular confirmation.

Adult-onset leukoencephalopathies are clinically and pathologically heterogeneous diseases, characterized by overlapping clinical and neuroradiological features and a difficult diagnostic process. Nevertheless, knowledge of the metabolic and genetic basis of leukoencephalopathies is constantly increasing. This article provides an overview of currently known leukoencephalopathies in adulthood, emphasizing, in addition to the classical forms, their atypical clinical presentations. In particular, we review the clinical spectrum and the molecular pathogenesis of certain adult-onset leukoencephalopathies, including cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), cerebroretinal microangiopathy with calcifications and cysts (CRMCC), hereditary diffuse leukoencephalopathy with spheroids (HDLS), fragile X-associated tremor/ataxia syndrome (FXTAS), vanishing white matter disease (VWM), autosomal dominant leukodystrophy due to lamin B1 duplication (ADLD), and vascular leukoencephalopathy mapping to chromosome 20q13.

Adult-onset leukodystrophy: review of 3 clinicopathologic phenotypes and a proposed classification.

Adult-onset leukodystrophies are clinically and pathologically heterogeneous diseases, and the overlapping morphologic features among these disorders can lead to confusion in pathologic classification. We report 3 recent autopsy cases that illustrate the clinicopathologic distinction between the 3 entities. The first, autosomal dominant leukodystrophy, is characterized clinically by early autonomic dysfunction and genetically by LMNB1 (lamin B1 gene) duplication. Recently, another clinical subtype emerged without the early autonomic dysfunction but with a similar genetic abnormality documented in 1 family. We reviewed the reported autopsy cases and show that both clinical subtypes share distinctive pathologic features. Other forms of adult-onset leukodystrophy can be classified based on the histologic evidence of the primary pathologic processes. A case of axonopathy with secondary demyelination serves as a prototype for adult-onset leukoencephalopathy/leukodystrophy with axonal spheroids; the genetic mutation of CSF1R (colony stimulating factor 1R) was recently discovered in patients with this disorder. A case of a primary demyelinating disease with no other distinctive pathologic features is designated as orthochromatic leukodystrophy. Pigmented glia can be present in both of the latter two categories and should not be used as a differentiating diagnostic feature. Based on the observations of our cases and literature review, we propose an algorithm for a practical diagnostic approach to adult-onset leukodystrophies.

MRI signatures of brain macrostructural atrophy and microstructural degradation in frontotemporal lobar degeneration subtypes.

Brain magnetic resonance imaging (MRI) studies have demonstrated regional patterns of brain macrostructural atrophy and white matter microstructural alterations separately in the three major subtypes of frontotemporal lobar degeneration (FTLD), which includes behavioral variant frontotemporal dementia (bvFTD), semantic dementia (SD), and progressive nonfluent aphasia (PNFA). This study was to investigate to what extent the pattern of white matter microstructural alterations in FTLD subtypes mirrors the pattern of brain atrophy, and to compare the ability of various diffusion tensor imaging (DTI) indices in characterizing FTLD patients, as well as to determine whether DTI measures provide greater classification power for FTLD than measuring brain atrophy. Twenty-five patients with FTLD (13 with bvFTD, 6 with SD, and 6 with PNFA) and 19 healthy age-matched control subjects underwent both structural MRI and DTI scans. Measurements of regional brain atrophy were based on T1-weighted MRI data and voxel-based morphometry. Measurements of regional white matter degradation were based on voxelwise as well as regions-of-interest tests of DTI variations, expressed as fractional anisotropy, axial diffusivity, and radial diffusivity. Compared to controls, bvFTD, SD, and PNFA patients each exhibited characteristic regional patterns of brain atrophy and white matter damage. DTI overall provided significantly greater accuracy for FTLD classification than brain atrophy. Moreover, radial diffusivity was more sensitive in assessing white matter damage in FTLD than other DTI indices. The findings suggest that DTI in general and radial diffusivity in particular are more powerful measures for the classification of FTLD patients from controls than brain atrophy.

Individual classification of mild cognitive impairment subtypes by support vector machine analysis of white matter DTI.

BACKGROUND AND PURPOSE: MCI was recently subdivided into sd-aMCI, sd-fMCI, and md-aMCI. The current investigation aimed to discriminate between MCI subtypes by using DTI. MATERIALS AND METHODS: Sixty-six prospective participants were included: 18 with sd-aMCI, 13 with sd-fMCI, and 35 with md-aMCI. Statistics included group comparisons using TBSS and individual classification using SVMs. RESULTS: The group-level analysis revealed a decrease in FA in md-aMCI versus sd-aMCI in an extensive bilateral, right-dominant network, and a more pronounced reduction of FA in md-aMCI compared with sd-fMCI in right inferior fronto-occipital fasciculus and inferior longitudinal fasciculus. The comparison between sd-fMCI and sd-aMCI, as well as the analysis of the other diffusion parameters, yielded no significant group differences. The individual-level SVM analysis provided discrimination between the MCI subtypes with accuracies around 97%. The major limitation is the relatively small number of cases of MCI. CONCLUSIONS: Our data show that, at the group level, the md-aMCI subgroup has the most pronounced damage in white matter integrity. Individually, SVM analysis of white matter FA provided highly accurate classification of MCI subtypes.

[Adult-onset hereditary leukoencephalopathy: classification and molecular basis of the disorder].

Adult-onset leukoencephalopathy involving the white matter of the brain is a heterogeneous disorder that exhibits a wide range of clinical manifestations. Recent advances in molecular genetics enable gene-based diagnosis of some forms of adult-onset leukoencephalopathy. In this review, the classification of adult-onset leukoencephalopathy based on molecular genetic findings is proposed. The autosomal dominant forms of adult-onset leukoencephalopathy include hereditary diffuse leukoencephalopathy with spheroids (HDLS), autosomal dominant adult-onset leukoencephalopathy (ALDL), cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and Alexander disease. The autosomal recessive forms of adult-onset leukoencephalopathy include cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), vanishing white matter (VWM) with leukoencephalopathy, Nasu-Hakola disease, and metachromatic leukodystrophy (MDL). X-chromosome-linked disorders include fragile X-associated tremor and ataxia syndrome (FXTAS) and adrenoleukodystrophy (ALD). Identification of the genes responsible for adult-onset leukoencephalopathy provides an important clue for elucidation of molecular pathophysiology underlying white matter disorders. One example is the identification of mutations in colony stimulating factor 1 receptor (CSF-1R) in patients with HDLS. Missense and splice site mutations have been found in the tyrosine kinase domain of CSF-1R. CSF-1R is highly expressed in microglia in the brain. It has been demonstrated that mice depleted of CSF-1R exhibit loss of microglia in the brain. In addition, stimulation of IL-34, a ligand of CSF-1R, induces proliferation and activation of microglia. These findings raise an intriguing possibility that dysfunction of microglia may play a role in the pathogenesis of white matter lesions occurring in patients with HDLS.

MRI characteristics and scoring in HDLS due to CSF1R gene mutations.

OBJECTIVE: To describe the brain MRI characteristics of hereditary diffuse leukoencephalopathy with spheroids (HDLS) with known mutations in the colony-stimulating factor 1 receptor gene (CSF1R) on chromosome 5. METHODS: We reviewed 20 brain MRI scans of 15 patients with autopsy- or biopsy-verified HDLS and CSF1R mutations. We assessed sagittal T1-, axial T1-, T2-, proton density-weighted and axial fluid-attenuated inversion recovery images for distribution of white matter lesions (WMLs), gray matter involvement, and atrophy. We calculated a severity score based on a point system (0-57) for each MRI scan. RESULTS: Of the patients, 93% (14 of 15) demonstrated localized WMLs with deep and subcortical involvement, whereas one patient revealed generalized WMLs. All WMLs were bilateral but asymmetric and predominantly frontal. Fourteen patients had a rapidly progressive clinical course with an initial MRI mean total severity score of 16.7 points (range 10-33.5). Gray matter pathology and brainstem atrophy were absent, and the corticospinal tracts were involved late in the disease course. There was no enhancement, and there was minimal cerebellar pathology. CONCLUSION: Recognition of the typical MRI patterns of HDLS and the use of an MRI severity score might help during the diagnostic evaluation to characterize the natural history and to monitor potential future treatments. Indicators of rapid disease progression were symptomatic disease onset before 45 years, female sex, WMLs extending beyond the frontal regions, a MRI severity score greater than 15 points, and mutation type of deletion.

Comprehensive immunohistochemical studies on canine necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME).

In dogs, there are several idiopathic meningoencephalitides, such as necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME). Although they are often assumed to be immune mediated, the etiology of these diseases remains elusive. In this study, the histopathology of the lesions caused by these conditions and the inflammatory cell populations produced in response to them were examined among dogs affected with GME, NME, or NLE to understand their pathogeneses. The brain tissues of dogs with NME (n = 25), NLE (n = 5), or GME (n = 9) were used. The inflammatory cells were identified by immunohistochemistry using antibodies against CD3, IgG, CD20, CD79acy, and CD163. In NME and NLE, malacic changes were located in the cerebral cortex, as well as the cerebral white matter and thalamus, respectively. The distribution of the brain lesions in NME and NLE was breed specific. In GME, granulomatous lesions that were mostly composed of epithelioid macrophages were observed in the cerebral white matter, cerebellum, and brainstem. Although the proportions of IgG-, CD20-, and CD79acy-positive cells (B cells) were not significantly different among the GME, NME, and NLE lesions, that of CD3-positive cells (T cells) was increased in GME. In NME and NLE, CD163-positive cells (macrophages) had diffusely infiltrated the cerebral cortex and white matter, respectively. However, in GME, CD163-positive cells accumulated around the blood vessels in the cerebral and cerebellar white matter. The distributions of these lesions were quite different among GME, NME, and NLE, whereas there were no marked differences in the proportions of inflammatory cells.

Neuropsychiatric systemic lupus erythematosus: lessons learned from magnetic resonance imaging.

OBJECTIVE: The clinical manifestations of nervous system involvement in systemic lupus erythematosus (neuropsychiatric SLE [NPSLE]) are highly diverse, and their etiology is incompletely understood. The aim of this study was to provide an inventory of abnormalities on conventional brain magnetic resonance imaging (MRI) in NPSLE and to interpret the findings in relation to possible underlying pathogenetic mechanisms. METHODS: MR images of the first episode of active NPSLE in 74 patients were retrospectively reviewed. All patients fulfilled the American College of Rheumatology (ACR) 1982 revised criteria for the classification of SLE and were classified according to the 1999 ACR case definitions for NPSLE syndromes. We excluded patients with a history of brain disease and patients in whom other mechanisms unrelated to SLE caused the neuropsychiatric symptoms. RESULTS: The principal findings were: 1) focal hyperintensities in white matter (WM) (49% of all patients) or both WM and gray matter (GM) (5% of all patients), suggestive of vasculopathy or vasculitis; 2) more widespread, confluent hyperintensities in the WM, suggestive of chronic hypoperfusion due to the same mechanisms; 3) diffuse cortical GM lesions (12% of all patients), compatible with an immune response to neuronal components or postseizure changes; and 4) absence of MRI abnormalities, despite signs and symptoms of active disease (42% of all patients). CONCLUSION: Several distinct brain MRI patterns were observed in patients with active NPSLE, suggestive of different pathogenetic mechanisms. To advance our understanding of the various processes leading to NPSLE, the radiographic manifestations may be a good starting point and useful for categorization of patients in further research.

Correlation of quantitative diffusion tensor tractography with clinical grades of subacute sclerosing panencephalitis.

BACKGROUND AND PURPOSE: SSPE is a persistent infection of the central nervous system caused by the measles virus. The correlation between the clinical staging and conventional MR imaging is usually poor. The purpose of this study was to determine whether tract-specific DTI measures in the major white mater tracts correlate with clinical grades as defined by the Jabbour classification for SSPE. MATERIALS AND METHODS: Quantitative DTT was performed on 20 patients with SSPE (mean age, 9 years) and 14 age- and sex-matched controls. All patients were graded on the basis of the Jabbour classification into grade II (n=9), grade III (n=6), and grade IV (n=5) SSPE. The major white matter tracts quantified included the CC, SLF, ILF, CST, CNG, SCP, MCP, ICP, ATR, STR, and PTR. RESULTS: Although a successive decrease in mean FA values was observed in all the fiber tracts except for the SCP and ICP, moving from controls to grade IV, a significant inverse correlation between clinical grade and mean FA values was observed only in the splenium (r=-0.908, P<.001), CST (r=-0.663, P=.013), SLF (r=-0.533, P=.050), ILF (r=-0.776, P=.001), STR (r=-0.538, P=.047), and PTR (r=-0.686, P=.035) fibers. No significant correlation of mean MD values from these white matter tracts was observed with clinical grades of the disease. CONCLUSIONS: We conclude that the grade of encephalopathy correlates inversely with the tract-specific mean FA values. This information may be valuable in studying the disease progression with time and in assessing the therapeutic response in the future.