Pure and syndromic optic atrophy explained by deep intronic OPA1 mutations and an intralocus modifier.

The genetic diagnosis in inherited optic neuropathies often remains challenging, and the emergence of complex neurological phenotypes that involve optic neuropathy is puzzling. Here we unravel two novel principles of genetic mechanisms in optic neuropathies: deep intronic OPA1 mutations, which explain the disease in several so far unsolved cases; and an intralocus OPA1 modifier, which explains the emergence of syndromic 'optic atrophy plus' phenotypes in several families. First, we unravelled a deep intronic mutation 364 base pairs 3' of exon 4b in OPA1 by in-depth investigation of a family with severe optic atrophy plus syndrome in which conventional OPA1 diagnostics including gene dosage analyses were normal. The mutation creates a new splice acceptor site resulting in aberrant OPA1 transcripts with retained intronic sequence and subsequent translational frameshift as shown by complementary DNA analysis. In patient fibroblasts we demonstrate nonsense mediated messenger RNA decay, reduced levels of OPA1 protein, and impairment of mitochondrial dynamics. Subsequent site-specific screening of >360 subjects with unexplained inherited optic neuropathy revealed three additional families carrying this deep intronic mutation and a base exchange four nucleotides upstream, respectively, thus confirming the clinical significance of this mutational mechanism. Second, in all severely affected patients of the index family, the deep intronic mutation occurred in compound heterozygous state with an exonic OPA1 missense variant (p.I382M; NM_015560.2). The variant alone did not cause a phenotype, even in homozygous state indicating that this long debated OPA1 variant is not pathogenic per se, but acts as a phenotypic modifier if it encounters in trans with an OPA1 mutation. Subsequent screening of whole exomes from >600 index patients identified a second family with severe optic atrophy plus syndrome due to compound heterozygous p.I382M, thus confirming this mechanism. In summary, we provide genetic and functional evidence that deep intronic mutations in OPA1 can cause optic atrophy and explain disease in a substantial share of families with unsolved inherited optic neuropathies. Moreover, we show that an OPA1 modifier variant explains the emergence of optic atrophy plus phenotypes if combined in trans with another OPA1 mutation. Both mutational mechanisms identified in this study-deep intronic mutations and intragenic modifiers-might represent more generalizable mechanisms that could be found also in a wide range of other neurodegenerative and optic neuropathy diseases.

Improved localization of language areas using single voxel signal analysis of unprocessed fMRI data.

Activated brain regions can be visualized and localized with the use of fMRI (functional magnetic imaging). This is based on changes in the blood flow in activated regions, or more precisely on the hemodynamic response function (HRF) and the Blood-Oxygen-Level-Dependent (BOLD) effect. This study used a task-based fMRI examination with language paradigms in order to stimulate the language areas. The measured fMRI data are frequently altered by different preprocessing steps for the analysis and the display of activations. These changes can lead to discrepancies between the displayed and the truly measured location of the activations. Simple t-maps were created with unprocessed fMRI data, to provide a more realistic representation of the language areas. HRF-dependent single-voxel fMRI signal analysis was performed to improve the analyzability of these activation maps.

[Magnetic resonance imaging in neuro-ophthalmological diagnostics]. / Magnetresonanztomografie in der neuroophthalmologischen Diagnostik.

Magnetic resonance imaging has become the most important tomographic imaging technique in neuro-ophthalmological diagnostics. A short introduction to the basic physical principles of MRI followed by a glossary summarising the relevant sequences used in neuro-ophthalmologic diagnostics provides an insight into this complex method. Differences and specific diagnostic values of every sequence are demonstrated with the help of sample images.

CNS involvement occurs more frequently in patients with Behçet's disease under cyclosporin A (CSA) than under other medications--results of a retrospective analysis of 117 cases.

The aim of this study was to evaluate the incidence of neurological manifestations of Behçet's disease (BD) in patients on cyclosporin A (CSA) compared with those on other medications. The records of 117 patients with BD who visited our hospital between 1990 and 2003 were reviewed with respect to symptoms and medication. All episodes of constant therapy prior to central nervous system (CNS) involvement were counted, and then the associations were analysed by the exact Fisher-Freeman-Halton test and adjusted for multiple tests by the Bonferroni-Holm method. We observed ten new cases of CNS manifestations in our patients with BD being regularly seen and treated in our tertiary care centre. The overall prevalence of neuro-BD in our patient group was 8.5%. In a retrospective analysis, the incidence of new-onset neurological disease (neuro-BD) in all patients with BD who regularly visited our hospital was significantly higher in patients on CSA than in those on other medications (6 of 21 vs 0 of 175 episodes, P<0.0001). This contrasts the obvious efficacy of CSA on extracerebral manifestations of BD, such as severe ocular disease, mucocutaneous lesions or arthritis. CSA exerts differential efficacy on various manifestations of BD. It is very effective for severe ocular and other moderate to severe manifestations of BD, but its efficacy for the prevention of neuro-BD seems to be inferior to that of other medications used in BD, such as azathioprine or interferon-alpha. The reasons for this are unclear, but the potential toxic effects of CSA on the CNS may be a predisposing factor for CNS vasculitis in BD.

Parameterization of the Age-Dependent Whole Brain Apparent Diffusion Coefficient Histogram.

PURPOSE: The distribution of apparent diffusion coefficient (ADC) values in the brain can be used to characterize age effects and pathological changes of the brain tissue. The aim of this study was the parameterization of the whole brain ADC histogram by an advanced model with influence of age considered. METHODS: Whole brain ADC histograms were calculated for all data and for seven age groups between 10 and 80 years. Modeling of the histograms was performed for two parts of the histogram separately: the brain tissue part was modeled by two Gaussian curves, while the remaining part was fitted by the sum of a Gaussian curve, a biexponential decay, and a straight line. RESULTS: A consistent fitting of the histograms of all age groups was possible with the proposed model. CONCLUSIONS: This study confirms the strong dependence of the whole brain ADC histograms on the age of the examined subjects. The proposed model can be used to characterize changes of the whole brain ADC histogram in certain diseases under consideration of age effects.

Age-dependent changes in the histogram of apparent diffusion coefficients values in magnetic resonance imaging.

The aim of this study was to develop a fast method for estimating whether a brain volume loss is within the normal range for the respective age of the patient. A readout-segmented diffusion-weighted echo-planar imaging sequence was performed as part of the routine examination at a 3-T scanner. Data without (b0-image) and with diffusion weighting (1000 s/mm(2)) from 492 patients were examined (in the age from 3 to 89 years). One hundred and seventy-three data-sets had to be excluded due to brain lesions or to pathological enlarged cerebrospinal fluid spaces. In the remaining 319 data-sets, apparent diffusion coefficients (ADCs) values were calculated for all pixels exceeding a combined threshold in the diffusion-weighted data and in the non-diffusion-weighted data. The first part of the histogram represents pixels containing mostly brain tissue. The percentage of number of pixels in this part of the ADC histograms was evaluated for all patients and was correlated with the age of the patients. In all the areas examined, a monotone change of relative pixel numbers with the age of the patients was found. The reduction of the contribution of pixels containing mostly brain tissue accelerated with age and was found to be 0.18%/year in the age of 20, 0.34%/year in the age of 50, and 0.50%/year in the age of 80. The observed decrease of the relative number of pixels from the brain tissue with increasing age corresponds to previously published results based on more time-consuming 3-D measurements. The presented technique uses a conventional clinical sequence and might be helpful in deciding whether an observed brain volume loss in a patient is within the normal range for the age of the patient.