MRI-based thalamic volumetry in multiple sclerosis using FSL-FIRST: Systematic assessment of common error modes.

BACKGROUND AND PURPOSE: FSL's FMRIB's Integrated Registration and Segmentation Tool (FSL-FIRST) is a widely used and well-validated tool. Automated thalamic segmentation is a common application and an important longitudinal measure for multiple sclerosis (MS). However, FSL-FIRST's algorithm is based on shape models derived from non-MS groups. As such, the present study sought to systematically assess common thalamic segmentation errors made by FSL-FIRST on MRIs from people with multiple sclerosis (PwMS). METHODS: FSL-FIRST was applied to generate thalamic segmentation masks for 890 MR images in PwMS. Images and masks were reviewed systematically to classify and quantify errors, as well as associated anatomical variations and MRI abnormalities. For cases with overt errors (n = 362), thalamic masks were corrected and quantitative volumetric differences were calculated. RESULTS: In the entire quantitative volumetric group, the mean volumetric error of FSL-FIRST was 2.74% (0.360 ml): among only corrected cases, the mean volumetric error was 6.79% (0.894 ml). The average percent volumetric error associated with seven error types, two anatomical variants, and motions artifacts are reported. Additional analyses showed that the presence of motion artifacts or anatomical variations significantly increased the probability of error (χ2  = 18.14, p < .01 and χ2  = 64.89, p < .001, respectively). Finally, thalamus volume error was negatively associated with degree of atrophy, such that smaller thalami were systematically overestimated (r = -.28, p < .001). CONCLUSIONS: In PwMS, FSL-FIRST thalamic segmentation miscalculates thalamic volumetry in a predictable fashion, and may be biased to overestimate highly atrophic thalami. As such, it is recommended that segmentations be reviewed and corrected manually when appropriate for specific studies.

Decreasing brain iron in multiple sclerosis: The difference between concentration and content in iron MRI.

Increased brain iron concentration is often reported concurrently with disease development in multiple sclerosis (MS) and other neurodegenerative diseases. However, it is unclear whether the higher iron concentration in patients stems from an influx of iron into the tissue or a relative reduction in tissue compartments without much iron. By taking into account structural volume, we investigated tissue iron content in the deep gray matter (DGM) over 2 years, and compared findings to previously reported changes in iron concentration. 120 MS patients and 40 age- and sex-matched healthy controls were included. Clinical testing and MRI were performed both at baseline and after 2 years. Overall, iron content was calculated from structural MRI and quantitative susceptibility mapping in the thalamus, caudate, putamen, and globus pallidus. MS patients had significantly lower iron content than controls in the thalamus, with progressive MS patients demonstrating lower iron content than relapsing-remitting patients. Over 2 years, iron content decreased in the DGM of patients with MS, while it tended to increase or remain stable among controls. In the thalamus, decreasing iron content over 2 years was associated with disability progression. Our study showed that temporally increasing magnetic susceptibility in MS should not be considered as evidence for iron influx because it may be explained, at least partially, by disease-related atrophy. Declining DGM iron content suggests that, contrary to the current understanding, iron is being removed from the DGM in patients with MS.

Long-standing multiple sclerosis neurodegeneration: volumetric magnetic resonance imaging comparison to Parkinson's disease, mild cognitive impairment, Alzheimer's disease, and elderly healthy controls.

Multiple sclerosis (MS) exhibits neurodegeneration driven disability progression. We compared the extent of neurodegeneration among 112 long-standing MS patients, 37 Parkinson's disease (PD) patients, 34 amnestic mild cognitive impairment (aMCI) patients, 37 Alzheimer's disease (AD) patients, and 184 healthy controls. 3T MRI volumes of whole brain (WBV), white matter (WMV), gray matter (GMV), cortical (CV), deep gray matter (DGM), and nuclei-specific volumes of thalamus, caudate, putamen, globus pallidus, and hippocampus were derived with SIENAX and FIRST software. Аge and sex-adjusted analysis of covariance was used. WBV was not significantly different between diseases. MS had significantly lower WMV compared to other disease groups (p < 0.021). Only AD had smaller GMV and CV when compared to MS (both p < 0.001). MS had smaller DGM volume than PD and aMCI (p < 0.001 and p = 0.026, respectively) and lower thalamic volume when compared to all other neurodegenerative diseases (p < 0.008). Long-standing MS exhibits comparable global atrophy with lower WMV and thalamic volume when compared to other classical neurodegenerative diseases.

Pathological cut-offs of global and regional brain volume loss in multiple sclerosis.

BACKGROUND: Volumetric MRI surrogate markers of disease progression are lacking. OBJECTIVE: To establish cut-off values of brain volume loss able to discriminate between healthy controls and MS patients. METHODS: In total, 386 patients after first demyelinating event suggestive of MS (CIS), 964 relapsing-remitting MS (RRMS) patients, 63 secondary-progressive MS (SPMS) patients and 58 healthy controls were included in this longitudinal study. A total of 11,438 MRI scans performed on the same MRI scanner with the same protocol were analysed. Annualised percentage changes of whole brain, grey matter, thalamus and corpus callosum volumes were estimated. We investigated cut-offs able to discriminate between healthy controls and MS patients. RESULTS: At a predefined specificity of 90%, the annualised percentage change cut-off of corpus callosum volume (-0.57%) was able to distinguish between healthy controls and patients with the highest sensitivity (51% in CIS, 48% in RRMS and 42% in SPMS patients). Lower sensitivities (22%-49%) were found for cut-offs of whole brain, grey matter and thalamic volume loss. Among CIS and RRMS patients, cut-offs were associated with greater accumulation of disability. CONCLUSION: We identified cut-offs of annualised global and regional brain volume loss rates able to discriminate between healthy controls and MS patients.

Brain Iron at Quantitative MRI Is Associated with Disability in Multiple Sclerosis.

Purpose To study deep gray matter susceptibility in multiple sclerosis (MS) by using quantitative susceptibility mapping (QSM) and to assess the relationship between susceptibility and clinical disability. Materials and Methods For this prospective study between March 2009 and November 2013, 600 participants with MS (452 with relapsing-remitting MS and 148 with secondary progressive MS) and 250 age- and sex-matched healthy control participants were imaged with 3.0-T MRI to measure magnetic susceptibility. Deep gray matter susceptibility (in parts per billion) was analyzed by using region of interest and voxelwise methods. QSM and MRI volumetric differences between study groups and associations with clinical outcomes were assessed. Analysis of covariance, multivariable linear regression, and voxelwise analyses, controlling for age and sex, were used to compare study groups and to explore associations between MRI and clinical outcomes. Results Compared with control participants, participants with MS presented with lower thalamic susceptibility (-7.5 ppb vs -1.1 ppb; P < .001) and higher susceptibility of basal ganglia (62 ppb vs 54.8 ppb; P < .001). Lower thalamic susceptibility was associated with longer disease duration (ß = -0.42; P = .002), higher degree of disability (ß = -0.64; P = .03), and secondary-progressive course (ß = -4.3; P = .009). Higher susceptibility of the globus pallidus was associated with higher disability (ß = 2; P = .03). After correcting for each individual structural volume in voxelwise analysis, lower thalamic susceptibility and higher susceptibility of the globus pallidus remained associated with clinical disability (P < .05). Conclusion Quantitative susceptibility mapping (QSM) suggests that altered deep gray matter iron is associated with the evolution of multiple sclerosis (MS) and on disability accrual, independent of tissue atrophy. © RSNA, 2018 Online supplemental material is available for this article.

Thalamic white matter in multiple sclerosis: A combined diffusion-tensor imaging and quantitative susceptibility mapping study.

Thalamic white matter (WM) injury in multiple sclerosis (MS) remains relatively poorly understood. Combining multiple imaging modalities, sensitive to different tissue properties, may aid in further characterizing thalamic damage. Forty-five MS patients and 17 demographically-matched healthy controls (HC) were scanned with 3T MRI to obtain quantitative measures of diffusivity and magnetic susceptibility. Participants underwent cognitive evaluation with the Brief International Cognitive Assessment for Multiple Sclerosis battery. Tract-based spatial statistics identified thalamic WM. Non-parametric combination (NPC) analysis was used to perform joint inference on fractional anisotropy (FA), mean diffusivity (MD) and magnetic susceptibility measures. The association of surrounding WM lesions and thalamic WM pathology was investigated with lesion probability mapping. Compared to HCs, the greatest extent of thalamic WM damage was reflected by the combination of increased MD and decreased magnetic susceptibility (63.0% of thalamic WM, peak p = .001). Controlling for thalamic volume resulted in decreased FA and magnetic susceptibility (34.1%, peak p = .004) as showing the greatest extent. In MS patients, the most widespread association with information processing speed was found with the combination of MD and magnetic susceptibility (67.6%, peak p = .0005), although this was not evident after controlling for thalamic volume. For memory measures, MD alone yielded the most widespread associations (45.9%, peak p = .012 or 76.7%, peak p = .001), even after considering thalamic volume, albeit with smaller percentages. White matter lesions were related to decreased FA (peak p = .0063) and increased MD (peak p = .007), but not magnetic susceptibility, of thalamic WM. Our study highlights the complex nature of thalamic pathology in MS.

Mapping of thalamic magnetic susceptibility in multiple sclerosis indicates decreasing iron with disease duration: A proposed mechanistic relationship between inflammation and oligodendrocyte vitality.

Recent advances in susceptibility MRI have dramatically improved the visualization of deep gray matter brain regions and the quantification of their magnetic properties in vivo, providing a novel tool to study the poorly understood iron homeostasis in the human brain. In this study, we used an advanced combination of the recent quantitative susceptibility mapping technique with dedicated analysis methods to study intra-thalamic tissue alterations in patients with clinically isolated syndrome (CIS) and multiple sclerosis (MS). Thalamic pathology is one of the earliest hallmarks of MS and has been shown to correlate with cognitive dysfunction and fatigue, but the mechanisms underlying the thalamic pathology are poorly understood. We enrolled a total of 120 patients, 40 with CIS, 40 with Relapsing Remitting MS (RRMS), and 40 with Secondary Progressive MS (SPMS). For each of the three patient groups, we recruited 40 controls, group matched for age- and sex (120 total). We acquired quantitative susceptibility maps using a single-echo gradient echo MRI pulse sequence at 3 T. Group differences were studied by voxel-based analysis as well as with a custom thalamus atlas. We used threshold-free cluster enhancement (TFCE) and multiple regression analyses, respectively. We found significantly reduced magnetic susceptibility compared to controls in focal thalamic subregions of patients with RRMS (whole thalamus excluding the pulvinar nucleus) and SPMS (primarily pulvinar nucleus), but not in patients with CIS. Susceptibility reduction was significantly associated with disease duration in the pulvinar, the left lateral nuclear region, and the global thalamus. Susceptibility reduction indicates a decrease in tissue iron concentration suggesting an involvement of chronic microglia activation in the depletion of iron from oligodendrocytes in this central and integrative brain region. Not necessarily specific to MS, inflammation-mediated iron release may lead to a vicious circle that reduces the protection of axons and neuronal repair.

Thalamus volume and ambulation in multiple sclerosis: a cross-sectional study.

AIM: This cross-sectional study examined if subcortical gray matter (SGM) structures accounted for differences in timed 25-foot walk (T25FW) speed between multiple sclerosis (MS) patients and controls. METHODS: Subjects underwent brain MRI and completed the T25FW. Volumes of the thalamus, caudate, putamen and pallidum were calculated from 3D T1-weighted structural brain images. T2 lesion volume (T2LV) was determined by using a semiautomated edge detection contouring-thresholding technique. RESULTS: There were differences in T25FW speed, SGM volumes and T2LV between MS and controls. T25FW speed was associated with SGM volumes and T2LV in MS and controls. Thalamic volume partially accounted for the difference in T25FW speed between the MS and controls. CONCLUSION: The reduction of thalamus volume is associated with compromised ambulation in MS patients.

Localized atrophy of the thalamus and slowed cognitive processing speed in MS patients.

BACKGROUND: Deep gray matter (DGM) atrophy is common in multiple sclerosis (MS), but no studies have investigated surface-based structure changes over time with respect to healthy controls (HCs). Moreover, the relationship between cognition and the spatio-temporal evolution of DGM atrophy is poorly understood. OBJECTIVES: To explore DGM structural differences between MS and HCs over time in relation to neuropsychological (NP) outcomes. METHODS: The participants were 44 relapsing-remitting and 20 secondary progressive MS patients and 22 HCs. All were scanned using 3T magnetic resonance imaging (MRI) at baseline and 3-year follow-up. NP examination emphasized consensus standard tests of processing speed and memory. We performed both volumetric and shape analysis of DGM structures and assessed their relationships with cognition. RESULTS: Compared to HCs, MS patients presented with significantly smaller DGM volumes. For the thalamus and caudate, differences in shape were mostly localized along the lateral ventricles. NP outcomes were related to both volume and shape of the DGM structures. Over 3 years, decreased cognitive processing speed was related to localized atrophy on the anterior and superior surface of the left thalamus. CONCLUSIONS: These findings highlight the role of atrophy in the anterior nucleus of the thalamus and its relation to cognitive decline in MS.

Humoral responses to herpesviruses are associated with neurodegeneration after a demyelinating event: results from the multi-center set study.

OBJECTIVES: To investigate the associations between antibody responses to herpesviruses and the development of thalamic, total deep gray matter, cortical and central atrophy in high-risk clinically isolated syndromes (CIS) after the first demyelinating event. METHODS: We analyzed volumetric brain outcomes in 193 CIS patients enrolled in a multi-center study of high-risk CIS. All patients had 2 or more MRI brain lesions and two or more oligoclonal bands in cerebrospinal fluid. Serum samples obtained at the screening visit prior to any treatment were analyzed for IgG antibodies against cytomegalovirus (anti-CMV) and Epstein-Barr virus (EBV) viral capsid antigen (VCA). All patients were treated with interferon-beta. Clinical and MRI assessments were obtained at baseline, 6, 12, and 24 months. RESULTS: Anti-EBV VCA highest quartile status was associated with regional atrophy measures for percent decrease in thalamus. Anti-CMV positivity was associated with greater total deep gray matter atrophy and whole brain atrophy. Anti-EBV VCA highest quartile status was associated as trends with greater whole brain, gray matter atrophy and central atrophy. The associations of anti-EBV VCA antibodies with thalamic atrophy were mediated by its associations with T2 lesions whereas the associations of anti-CMV positivity with deep gray matter atrophy were relatively independent of T2 lesions. CONCLUSIONS: Antibody responses to EBV and CMV are associated with global and regional brain atrophy in CIS patients treated with interferon-beta.

Lipid profiles are associated with lesion formation over 24 months in interferon-ß treated patients following the first demyelinating event.

OBJECTIVES: To investigate the associations of serum lipid profile with disease progression in high-risk clinically isolated syndromes (CIS) after the first demyelinating event. METHODS: High density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) were obtained in pretreatment serum from 135 high risk patients with CIS (≥ 2 brain MRI lesions and ≥ 2 oligoclonal bands) enrolled in the Observational Study of Early Interferon ß-1a Treatment in High Risk Subjects after CIS study (SET study), which prospectively evaluated the effect of intramuscular interferon ß-1a treatment following the first demyelinating event. Thyroid stimulating hormone, free thyroxine, 25-hydroxy vitamin D3, active smoking status and body mass index were also obtained. Clinical and MRI assessments were obtained within 4 months of the initial demyelinating event and at 6, 12 and 24 months. RESULTS: The time to first relapse and number of relapses were not associated with any of the lipid profile variables. Higher LDL-C (p=0.006) and TC (p=0.001) levels were associated with increased cumulative number of new T2 lesions over 2 years. Higher free thyroxine levels were associated with lower cumulative number of contrast-enhancing lesions (p=0.008). Higher TC was associated as a trend with lower baseline whole brain volume (p=0.020). Higher high density lipoprotein was associated with higher deseasonalised 1,25-dihydroxy vitamin D3 (p=0.003) levels and a trend was found for deseasonalised 25-hydroxy vitamin D3 (p=0.014). CONCLUSIONS: In early multiple sclerosis, lipid profile variables particularly LDL-C and TC levels are associated with inflammatory MRI activity measures.

Thalamic atrophy is associated with development of clinically definite multiple sclerosis.

PURPOSE: To investigate the association between the development of thalamic and cortical atrophy and the conversion to clinically definite multiple sclerosis (CDMS) in patients with clinically isolated syndrome (CIS). MATERIALS AND METHODS: This prospective study was approved by the institutional review board. Informed consent was given by 216 CIS patients, and patients were treated with 30 µg of intramuscular interferon ß1a once a week. They were assessed with a magnetic resonance (MR) imaging examination at baseline, 6 months, 1 year, and 2 years. Patients were evaluated within 4 months of an initial demyelinating event, had two or more brain lesions on MR images, and had two or more oligoclonal bands in cerebrospinal fluid. MR imaging measures of progression included cumulative number and volume of contrast agent-enhanced (CE) new and enlarged T2 lesions, and changes in whole-brain, tissue-specific global, and regional gray matter volumes. Regression and mixed-effect model analyses were used. RESULTS: Over 2 years, 92 of 216 patients (42.6%) converted to CDMS; 122 (56.5%) CIS patients fulfilled McDonald 2005 criteria and 153 (70.8%) fulfilled McDonald 2010 criteria for MR imaging dissemination in time and space. The mean time to first relapse was 3.1 months, and mean annual relapse rate was 0.46. In mixed-effect model analysis, the lateral ventricle volume (P = .005), accumulation of CE (P = .007), new total T2 (P = .009) and new enlarging T2 lesions (P = .01) increase, and thalamic (P = .009) and whole-brain (P = .019) volume decrease were associated with development of CDMS. In multivariate regression analysis, decrease in thalamic volumes and increase in lateral ventricle volumes (P = .009) were MR imaging variables associated with the development of CDMS. CONCLUSION: Measurement of thalamic atrophy and increase in ventricular size in CIS is associated with CDMS development and should be used in addition to the assessment of new T2 and CE lesions.

Clinical significance of atrophy and white matter mean diffusivity within the thalamus of multiple sclerosis patients.

BACKGROUND: Gray-matter (GM) atrophy is strongly predictive of cognitive impairment in multiple sclerosis (MS) patients. The thalamus is the region where the atrophy/cognition correlation is most robust. However, few studies have assessed diffusion tensor imaging (DTI) metrics within the thalamus. OBJECTIVE: This study was designed to determine if thalamus white matter DTI predicts cognitive impairment after accounting for the effects of volume loss. METHODS: We enrolled 75 MS patients and 18 healthy controls undergoing 3T brain magnetic resonance imaging (MRI). Thalamus volumes were calculated on 3D T1 images. Voxelwise analyses of DTI metrics were performed within the thalamic white matter tracts. Neuropsychological (NP) testing, acquired using consensus standard methods, contributed measures of memory, cognitive processing speed and executive function. RESULTS: All cognitive tests were significantly predicted (R (2) =0.31, p<0.001) by thalamus volume after accounting for influence of demographics. Mean diffusivity was retained in regression models predicting all cognitive tests, adding from 7-13% of additional explained variance (p<0.02) after accounting for thalamus volume. CONCLUSIONS: We confirm the significant role of thalamus atrophy in MS-associated cognitive disorder, and further report that subtle thalamus pathology as detected by DTI adds incremental explained variance in predicting cognitive impairment.

Interdependence and contributions of sun exposure and vitamin D to MRI measures in multiple sclerosis.

PURPOSE: To assess the relationships of sun exposure history, supplementation and environmental factors to vitamin D levels in multiple sclerosis (MS) patients and to evaluate the associations between sun exposure and MRI measures. METHODS: This study included 264 MS patients (mean age 46.9±10 years, disease duration 14.6±10 years; 67.8% relapsing-remitting, 28% secondary progressive and 4.2% primary progressive MS) and 69 healthy controls. Subjects underwent neurological and 3 T MRI examinations, provided blood samples and answered questions to a structured questionnaire. Information on race, skin and eye colour, supplement use, body mass index (BMI) and sun exposure was obtained by questionnaire. The vitamin D metabolites (25-hydroxy vitamin D3, 1, 25-dihydroxy vitamin D3 and 24, 25-dihydroxy vitamin D3) were measured using mass spectrometry. RESULTS: Multivitamin supplementation (partial correlation r(p)=0.29, p<0.001), BMI (r(p)=-0.24, p=0.001), summer sun exposure (r(p)=0.22, p=0.002) and darker eye colour (r(p)=-0.18, p=0.015) had the strongest associations with vitamin D metabolite levels in the MS group. Increased summer sun exposure was associated with increased grey matter volume (GMV, r(p)=0.16, p=0.019) and whole brain volume (WBV, r(p)=0.20, p=0.004) after correcting for Extended Disability Status Scale in the MS group. Inclusion of 25-hydroxy vitamin D3 levels did not substantially affect the positive associations of sun exposure with WBV (r(p)=0.18, p=0.003) and GMV (r(p)=0.14, p=0.026) in the MS group. CONCLUSIONS: Sun exposure may have direct effects on MRI measures of neurodegeneration in MS, independently of vitamin D.

Basal ganglia, thalamus and neocortical atrophy predicting slowed cognitive processing in multiple sclerosis.

Information-processing speed (IPS) slowing is a primary cognitive deficit in multiple sclerosis (MS). Basal ganglia, thalamus and neocortex are thought to have a key role for efficient information-processing, yet the specific relative contribution of these structures for MS-related IPS impairment is poorly understood. To determine if basal ganglia and thalamus atrophy independently contribute to visual and auditory IPS impairment in MS, after controlling for the influence of neocortical volume, we enrolled 86 consecutive MS patients and 25 normal controls undergoing 3T brain MRI and neuropsychological testing. Using Sienax and FIRST software, neocortical and deep gray matter (DGM) volumes were calculated. Neuropsychological testing contributed measures of auditory and visual IPS using the Paced Auditory Serial Addition Test (PASAT) and the Symbol Digit Modalities Test (SDMT), respectively. MS patients exhibited significantly slower IPS relative to controls and showed reduction in neocortex, caudate, putamen, globus pallidus, thalamus and nucleus accumbens volume. SDMT and PASAT were significantly correlated with all DGM regions. These effects were mitigated by controlling for the effects of neocortical volume, but all DGM volumes remained significantly correlated with SDMT, putamen (r = 0.409, p < 0.001) and thalamus (r = 0.362, p < 0.001) having the strongest effects, whereas for PASAT, the correlation was significant for putamen (r = 0.313, p < 0.01) but not for thalamus. We confirm the significant role of thalamus atrophy in MS-related IPS slowing and find that putamen atrophy is also a significant contributor to this disorder. These DGM structures have independent, significant roles, after controlling for the influence of neocortex atrophy.