Childhood white matter disorders: Research at the interface of MRI, clinical phenotype and genetics

promotiedatum: 4-4-2015 � prom-id: 1180

Novel hypomyelinating leukoencephalopathy affecting early myelinating structures.

Item does not contain fulltextOBJECTIVE: To describe 4 children with a novel hypomyelinating leukoencephalopathy, defined by a distinct pattern of magnetic resonance imaging (MRI) abnormalities. DESIGN: In our ongoing study on leukoencephalopathies of unknown origin, MRIs of patients are rated in a standardized manner. Patients are grouped according to their MRI abnormalities. The clinical and laboratory data are retrospectively reviewed. SUBJECTS: The MRIs of approximately 3000 patients with a leukoencephalopathy of unknown origin were initially evaluated. Four unrelated patients (all male, aged 1.8-7.4 years) displayed similar MRI alterations. RESULTS: Patients displayed mild T2 hyperintensity of the medulla oblongata, caudal part of the pons, hilus of the dentate nucleus, peridentate white matter, subcortical cerebellar white matter, optic radiation, and frontoparietal periventricular white matter. The posterior limb of the internal capsule showed alternating T2 hyperintense-hypointense-hyperintense stripes in 3 patients. The T1-weighted images showed hyperintensity, isointensity, or mild hypointensity of T2 hyperintense structures. The thalamus had a neonatal appearance with a mildly hyperintense signal except for a darker lateral part. Clinically, patients presented with nystagmus between ages 6 and 20 months. Over time, cerebellar ataxia and mild spasticity developed. All achieved unsupported walking. Cognition and language were normal. Known causes of hypomyelination were excluded. CONCLUSIONS: The patients share a striking pattern of MRI abnormalities and have a similar clinical picture, suggesting that they have the same disorder. The hypomyelination in this disorder specifically occurs in structures that normally myelinate early. We hypothesize that the disease is caused by a defect in a gene involved in early myelination.1 januari 201

Characteristics of Early MRI in Children and Adolescents with Vanishing White Matter

Objective MRI in vanishing white matter typically shows diffuse abnormality of the cerebral white matter, which becomes increasingly rarefied and cystic. We investigated the MRI characteristics preceding this stage. Design In a retrospective observational study, we evaluated all available MRIs in our database of DNA-confirmed VWM patients and selected MRIs without diffuse cerebral white matter abnormalities and without signs of rarefaction or cystic degeneration in patients below 20 years of age. A previously established scoring list was used to evaluate the MRIs. Results An MRI of seven patients fulfilled the criteria. All had confluent and symmetrical abnormalities in the periventricular and bordering deep white matter. In young patients, myelination was delayed. The inner rim of the corpus callosum was affected in all patients. Conclusions In early stages of VWM, MRI does not necessarily display diffuse cerebral white matter involvement and rarefaction or cystic degeneration. If the MRI abnormalities do not meet the criteria for VWM, it helps to look at the corpus callosum. If the inner rim (the callosal-septal interface) is affected, VWM should be considered. Copyright © 2012 by Thieme Medical Publishers, Inc

Magnetic resonance imaging pattern recognition in hypomyelinating disorders

Hypomyelination is observed in the context of a growing number of genetic disorders that share clinical characteristics. The aim of this study was to determine the possible role of magnetic resonance imaging pattern recognition in distinguishing different hypomyelinating disorders, which would facilitate the diagnostic process. Only patients with hypomyelination of known cause were included in this retrospective study. A total of 112 patients with Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus-Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis, Salla disease and fucosidosis were included. The brain scans were rated using a standard scoring list; the raters were blinded to the diagnoses. Grouping of the patients was based on cluster analysis. Ten clusters of patients with similar magnetic resonance imaging abnormalities were identified. The most important discriminating items were early cerebellar atrophy, homogeneity of the white matter signal on T2-weighted images, abnormal signal intensity of the basal ganglia, signal abnormalities in the pons and additional T2 lesions in the deep white matter. Eight clusters each represented mainly a single disorder (i.e. Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, infantile GM1 and GM2 gangliosidosis, Pelizaeus-Merzbacher-like disease and fucosidosis); only two clusters contained multiple diseases. Pelizaeus-Merzbacher-like disease was divided between two clusters and Salla disease did not cluster at all. This study shows that it is possible to separate patients with hypomyelination disorders of known cause in clusters based on magnetic resonance imaging abnormalities alone. In most cases of Pelizaeus-Merzbacher disease, hypomyelination with congenital cataract, hypomyelination with hypogonadotropic hypogonadism and hypodontia, Pelizaeus-Merzbacher-like disease, infantile GM1 and GM2 gangliosidosis and fucosidosis, the imaging pattern gives clues for the diagnosis. © 2010 The Author

Novel infantile-onset leukoencephalopathy with high lactate level and slow improvement.

Item does not contain fulltextOBJECTIVE: To describe a novel pattern of magnetic resonance imaging (MRI) abnormalities as well as the associated clinical and laboratory findings. DESIGN: The MRIs of more than 3000 patients with an unclassified leukoencephalopathy were systematically reviewed.Clinical and laboratory data were retrospectively collected.Setting: University hospital. PATIENTS: Seven patients (3 male) shared similar MRI abnormalities and clinical features. MAIN OUTCOME MEASURES: Pattern of MRI abnormalities and clinical and laboratory findings. RESULTS: The MRIs showed signal abnormalities of the deep cerebral white matter, corpus callosum, thalamus, basal ganglia,brainstem, and cerebellar white matter between the ages of 9 months and 2 years. On follow-up, abnormalities gradually improved. Clinical regression occurred in the second half-year of life with spasticity and loss of milestones.From the second year on, clinical improvement occurred.So far, no second episode of regression has happened.Lactate levels were elevated during clinical regression. CONCLUSION: These patients represent a single novel leukoencephalopathy,probably caused by a mitochondrial defect.1 juni 201

Early-onset LBSL: how severe does it get?

Aim?Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is known as a relatively mild leukoencephalopathy. We investigated the occurrence of severe variants of LBSL with extensive brain magnetic resonance imaging (MRI) abnormalities.Method?MRIs of approximately 3,000 patients with an unknown leukoencephalopathy were retrospectively reviewed for extensive signal abnormalities of the cerebral and cerebellar white matter, posterior limb of the internal capsule, cerebellar peduncles, pyramids, and medial lemniscus. Clinical data were retrospectively collected.Results?Eleven patients fulfilled the MRI criteria (six males); six had DARS2 mutations. Clinical and laboratory findings did not distinguish between patients with and without DARS2 mutations, but MRI did. Patients with DARS2 mutations more often had involvement of structures typically affected in LBSL, including decussatio of the medial lemniscus, anterior spinocerebellar tracts, and superior and inferior cerebellar peduncles. Also, involvement of the globus pallidus was associated with DARS2 mutations. Earliest disease onset was neonatal; earliest death at 20 months.Interpretation?This study confirms the occurrence of early infantile, severe LBSL, extending the known phenotypic range of LBSL. Abnormality of specific brainstem tracts and cerebellar peduncles are MRI findings that point to the correct diagnosis

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation: clinical and genetic characterization and target for therapy

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation is a disorder caused by recessive mutations in the gene DARS2, which encodes mitochondrial aspartyl-tRNA synthetase. Recent observations indicate that the phenotypic range of the disease is much wider than initially thought. Currently, no treatment is available. The aims of our study were (i) to explore a possible genotype-phenotype correlation; and (ii) to identify potential therapeutic agents that modulate the splice site mutations in intron 2 of DARS2, present in almost all patients. A cross-sectional observational study was performed in 78 patients with two DARS2 mutations in the Amsterdam and Helsinki databases up to December 2012. Clinical information was collected via questionnaires. An inventory was made of the DARS2 mutations in these patients and those previously published. An assay was developed to assess mitochondrial aspartyl-tRNA synthetase enzyme activity in cells. Using a fluorescence reporter system we screened for drugs that modulate DARS2 splicing. Clinical information of 66 patients was obtained. The clinical severity varied from infantile onset, rapidly fatal disease to adult onset, slow and mild disease. The most common phenotype was characterized by childhood onset and slow neurological deterioration. Full wheelchair dependency was rare and usually began in adulthood. In total, 60 different DARS2 mutations were identified, 13 of which have not been reported before. Except for 4 of 42 cases published by others, all patients were compound heterozygous. Ninety-four per cent of the patients had a splice site mutation in intron 2. The groups of patients sharing the same two mutations were too small for formal assessment of genotype-phenotype correlation. However, some combinations of mutations were consistently associated with a mild phenotype. The mitochondrial aspartyl-tRNA synthetase activity was strongly reduced in patient cells. Among the compounds screened, cantharidin was identified as the most potent modulator of DARS2 splicing. In conclusion, the phenotypic spectrum of leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation is wide, but most often the disease has a relatively slow and mild course. The available evidence suggests that the genotype influences the phenotype, but because of the high number of private mutations, larger numbers of patients are necessary to confirm this. The activity of mitochondrial aspartyl-tRNA synthetase is significantly reduced in patient cells. A compound screen established a 'proof of principle' that the splice site mutation can be influenced. This finding is promising for future therapeutic strategies. © 2013 The Author