The use of quantitative magnetic-resonance-based techniques to monitor the evolution of multiple sclerosis

A systematic review of repeatability and reproducibility studies of diffusion tensor imaging of cervical spinal cord

OBJECTIVES

Diffusion tensor imaging (DTI) techniques are being studied as a possible diagnostic and predictive tool for the evaluation of cervical spinal cord disease. This systematic review aims to evaluate the previous DTI studies that specifically investigated the repeatability and reproducibility of DTI in the cervical spinal cord.

METHODS AND MATERIALS

A search in the PubMed, Scopus, Web of Science and Ovid electronic databases was conducted for articles published between January 1990 and February 2022 that related to the repeatability and reproducibility of DTI in evaluating the cervical spinal cord using one of the following measurements: the intraclass correlation coefficient (ICC) and/or the coefficient of variation (CV), and/or Bland-Altman (BA) differences analysis methods. DTI studies that presented full statistical analysis of repeatability and/or reproducibility tests of the cervical spinal cord in peer-reviewed full-text publications published in journals were included. Articles that included at least one of the keywords within the titles or abstracts were identified. Additional full-text papers were found by searching the citations and reference lists of related articles. This review has followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance. Risk of bias was evaluated with 13 criteria weighted toward methodological quality of reported studies using the QuADS assessment criteria. This assessment only included full-text articles written in English.

RESULTS

A total of 11 studies were included and assessed for different characteristics, including sample size,(3-34) re-test time interval (<1 h to >3 months), test-retest reproducibility scores and acquisition method. Six studies used ICC which ranged from poor (ICC<0.37) to excellent reproducibility (ICC 0.91-0.99). Four studies reported an overall CV lower than 40% for all DTI metrics. Three studies reported the Bland-Altman (BA) differences and reported a minimum percentage showing no strong differences between repeated measurements. Quantitative analysis was not undertaken due to heterogeneity of methods. Repeatability and reproducibility measures were generally found to be good.

CONCLUSION

This study revealed that the application of DTI and its related measures in a clinical setting in the assessment of cervical spinal cord changes is feasible and reproducible. However, cervical spinal cord DTI suffers from some existing limitations that prevent it from being routinely used in research and clinical settings.

ADVANCES IN KNOWLEDGE

DTI with its parametric maps provide broad evaluation of the tissue structure of axonal white matter and are being studied as a possible diagnostic and predictive tool for the assessment of cervical spinal cord (CSC) disease.

Characterization of Radioiodinated Diaryl Oxadiazole Derivatives as SPECT Probes for Detection of Myelin in Multiple Sclerosis

Multiple sclerosis (MS) is an intractable disease of the central nervous system that results from destruction of the myelin sheath. Direct measurement of de- and remyelination is required for monitoring the disease stage of MS, but no useful method has been established. In this study, we characterized four diaryl oxadiazole derivatives as novel myelin-imaging probes for single photon emission computed tomography (SPECT). All the diaryl oxadiazole derivatives penetrated the blood-brain barrier in normal mice. Among them, the highest ratio of radioactivity accumulation in the white matter (myelin-rich region) against the gray matter (myelin-deficient region) was observed at 60 min postinjection of [¹²⁵I]1,3,4-PODP-DM in ex vivo autoradiography using normal mice. In the blocking study with ex vivo autoradiography, the radioactivity accumulation of [¹²⁵I]1,3,4-PODP-DM in the white matter markedly reduced. [¹²⁵I]1,3,4-PODP-DM detected demyelination in the ex vivo autoradiographic images of not only the spinal cord of the experimental autoimmune encephalomyelitis mice but also the brain after lysophosphatidylcholine (LPC) injection. In addition, [¹²³I]1,3,4-PODP-DM could image LPC-induced demyelination in the mouse brain with SPECT. These results suggest that [¹²³I]1,3,4-PODP-DM may be a potential SPECT probe for imaging myelin in MS.

Synthesis and biological evaluation of radioiodinated 3-phenylcoumarin derivatives targeting myelin in multiple sclerosis

Myelin is a lipid multilayer involved in the rate of nerve transmission, and its loss is a pathological feature of multiple sclerosis in brains. Since in vivo imaging of myelin may be useful for drug development, early diagnosis, and monitoring the disease stage, we designed, synthesized, and evaluated eight novel radioiodinated 3-phenylcoumarin derivatives as imaging probes targeting myelin. In the biodistribution study using normal mice, all compounds displayed sufficient brain uptake, ranging from 2.5 to 5.0% ID/g, at 2 min postinjection. On ex vivo autoradiography, [¹²⁵I]18 and [¹²⁵I]21, which have a dimethylamino group, showed high binding affinity for myelin in the normal mouse brain. In addition, the radioactivity accumulation of [¹²⁵I]21 in the white matter of the spinal cord in the experimental autoimmune encephalomyelitis mice was lower than that in naive mice. These results suggest that [¹²³I]21 shows potential as a single photon emission computed tomography probe targeting myelin.

Diffusion-weighted imaging of normal appearing corticospinal tracts in patients with multiple sclerosis

Aim To determine if there are differences in ADC values between normal appearing corticospinal tracks in patients with MS compared to ADC values in controls. Material and methods The study population comprised 62 consecutive MS patients (36 women and 26 men; mean age 36.45±8.63 years). 50 control subjects with no neurological disabilities or intracranial were included the study (32 women and 18 men; mean age 40.18±12.25 years). All ADC maps were independently evaluated by two experienced radiologists. ROI of approximately 15-18 mm² in capsula interna and 10-12 mm² in mesencephalon were placed bilaterally for measurement of ADC values. Three circular ROIs were placed-one each side for internal capsule-and 6 total ROIs from right and left internal capsule were averaged for each patient. Mesencephelon ADC measurements were performed similarly. Result The mean ADC values of the left internal capsule in MS patients were significiantly lower than the control group (p:0.002). No statistically significant difference was found between the MS patients and control group mean ADC values of the right internal capsule (p>0.05). The mean ADC values of the right and left mesencephalon in MS patients were significiantly lower than the control group (respectively; p:0.031, p<0.001). The mean ADC values of the left internal capsule were significiantly lower than the right internal capsule in MS patients (p<0.001). The mean ADC values of the left mesencephalon were significiantly lower than the right mesencephalon in MS patients (p<0.001). Conclusion The mean ADC values of the normal-appearing corticospinal tract in MS patients were significantly lower than the control group except for the right internal capsule.

The evaluation of MRI diffusion values of active demyelinating lesions in multiple sclerosis

BACKGROUND

Gadolinium (Gd) enhancement of lesions is the main radiologic marker for detection of activity in Multiple Sclerosis (MS). This study compares Diffusion weighted imaging (DWI) characteristics and enhancement to determine whether DWI can be used as an alternative to Gd administration.

METHODS

A retrospective study of 72 patients who had MRI with Gd and DWI. Visual assessment and comparison of the Apparent Diffusion Coefficient (ADC) values on Gd+ lesions, all lesions showing restricted diffusion, 2 Gd- lesions and 1 area of normal-appearing white matter (NAWM) in each MRI were performed.

RESULTS

DWI values were measured on 275 T2 lesions, 68 Gd+ and 207 Gd- lesions, as well as 104 NAWM. 34 Gd+ lesions showed restricted diffusion. The median ADC-minimum of Gd+ lesions was significantly lower than NAWM and even lower than Gd- lesions. Most DWI restricted lesions were also Gd+(specificity≥94%), however many Gd+ lesions did not show visually detectable restriction in DWI (sensitivity≤34%). The median ADC-minimum of symptomatic lesions was lower than asymptomatic lesions.

CONCLUSION

While Gd+ lesions have lower ADC-minimum, visual DWI assessment cannot replace Gd administration for identifying active lesions. Gd+ lesions showing restricted diffusion are clinically important as they are more likely associated with neurological symptoms.

Advances in multiple sclerosis and its variants: conventional and newer imaging techniques

Multiple sclerosis (MS) and its variants are inflammatory as well as neurodegenerative diseases that diffusely affect the central nervous system (CNS). There is a poor correlation between traditional imaging findings and symptoms in patients with MS. Current research in conventional magnetic resonance (MR) imaging of MS and related diseases includes optimization of hardware and pulse sequences and the development of automated and semiautomated techniques to measure and quantify disease burden. Advanced nonconventional MR techniques such as diffusion tensor and functional MR imaging probe the changes found in the CNS, and correlate these findings with clinical measures of disease.

Magnetization transfer imaging in premanifest and manifest huntington disease: a 2-year follow-up

BACKGROUND AND PURPOSE

MTI is a quantitative MR imaging technique that has recently demonstrated structural integrity differences between controls and patients with HD. Potentially, MTI can be used as a biomarker for monitoring disease progression. To establish the value of MTI as a biomarker, we aimed to examine the change in these measures during the course of HD.

MATERIALS AND METHODS

From the Leiden TRACK-HD study, 25 controls, 21 premanifest gene carriers, and 21 patients with manifest HD participated at baseline and during a 2-year follow-up visit. Brain segmentation of the cortical gray matter, white matter, caudate nucleus, putamen, pallidum, thalamus, amygdala, and hippocampus was performed by using the automated tools FAST and FIRST in FSL. Individual MTR values were calculated from these regions, and MTR histograms were constructed.

RESULTS

In the premanifest HD group stage "far from disease onset," a significant increase in MTR peak height of the putamen was observed with time. During the manifest HD stage, neither the mean MTR nor the MTR peak height showed a significant change during a 2-year follow-up.

CONCLUSIONS

MTI-derived measures are not suitable for monitoring in Huntington disease during a 2-year period because there was no decrease in structural integrity detected in any of the manifest HD groups longitudinally. The finding of increased putaminal MTR peak height in the premanifest far from disease onset group could relate to a predegenerative process, compensatory mechanisms, or aberrant development but should be interpreted with caution until future studies confirm this finding.

Magnetization transfer imaging in premanifest and manifest Huntington disease

BACKGROUND AND PURPOSE

MTI has the potential to detect abnormalities in normal-appearing white and gray matter on conventional MR imaging. Early detection methods and disease progression markers are needed in HD research. Therefore, we investigated MTI parameters and their clinical correlates in premanifest and manifest HD.

MATERIALS AND METHODS

From the Leiden TRACK-HD study, 78 participants (28 controls, 25 PMGC, 25 MHD) were included. Brain segmentation of cortical gray matter, white matter, caudate nucleus, putamen, pallidum, thalamus, amygdala, and hippocampus was performed using FSL's automated tools FAST and FIRST. Individual MTR values were calculated from these regions and MTR histograms constructed. Regression analysis of MTR measures from all gene carriers with clinical measures was performed.

RESULTS

MTR peak height was reduced in both cortical gray (P = .01) and white matter (P = .006) in manifest HD compared with controls. Mean MTR was also reduced in cortical gray matter (P = .01) and showed a trend in white matter (P = .052). Deep gray matter structures showed a uniform pattern of reduced MTR values (P < .05). No differences between premanifest gene carriers and controls were found. MTR values correlated with disease burden and motor and cognitive impairment.

CONCLUSIONS

Throughout the brain, disturbances in MTI parameters are apparent in early HD and are homogeneous across white and gray matter. The correlation of MTI with clinical measures indicates the potential to act as a disease monitor in clinical trials. However, our study does not provide evidence for MTI as a marker in premanifest HD.

A novel PET marker for in vivo quantification of myelination

C-11-labeled N-methyl-4,4'-diaminostilbene ([(11)C]MeDAS) was synthesized and evaluated as a novel radiotracer for in vivo microPET imaging of myelination. [(11)C]MeDAS exhibits optimal lipophilicity for brain uptake with a logP(oct) value of 2.25. Both in vitro and ex vivo staining exhibited MeDAS accumulation in myelinated regions such as corpus callosum and striatum. The corpus callosum region visualized by MeDAS is much larger in the hypermyelinated Plp-Akt-DD mouse brain than in the wild-type mouse brain, a pattern that was also consistently observed in Black-Gold or MBP antibody staining. Ex vivo autoradiography demonstrated that [(11)C]MeDAS readily entered the mouse brain and selectively labeled myelinated regions with high specificity. Biodistribution studies showed abundant initial brain uptake of [(11)C]MeDAS with 2.56% injected dose/whole brain at 5 min post injection and prolonged retention in the brain with 1.37% injected dose/whole brain at 60 min post injection. An in vivo pharmacokinetic profile of [(11)C]MeDAS was quantitatively analyzed through a microPET study in an Plp-Akt-DD hypermyelinated mouse model. MicroPET studies showed that [(11)C]MeDAS exhibited a pharmacokinetic profile that readily correlates the radioactivity concentration to the level of myelination in the brain. These studies suggest that MeDAS is a sensitive myelin probe that provides a direct means to detect myelin changes in the brain. Thus, it can be used as a myelin-imaging marker to monitor myelin pathology in vivo.

Correlation of cognitive dysfunction and diffusion tensor MRI measures in patients with mild and moderate multiple sclerosis

PURPOSE

To compare the diffusion tensor imaging (DTI) measures of multiple sclerosis (MS) patients and healthy subjects in every brain voxel and to correlate them with Paced Auditory Serial Addition Test (PASAT) scores.

MATERIALS AND METHODS

Fractional anisotropy (FA), and mean, longitudinal, and transverse diffusivity are compared between control subjects and MS patients, which were subdivided as mildly and moderately impaired. In addition, PASAT scores are correlated for both MS groups with the diffusion measures. An optimized voxel based analysis (VBA) method, in terms of coregistration, atlas construction, and image smoothing, was thereby used.

RESULTS

Diffusion differences between the control subjects and the patients with MS were found in the corpus callosum, inferior longitudinal fasciculus, cortico spinal tracts, forceps major, superior longitudinal fasciculus, and cingulum. In addition, we observed significant correlations of the FA and PASAT scores in the left inferior longitudinal fasciculus, the forceps minor, the capsula interna and externa, the genu of the corpus callosum, the left cingulum, the superior longitudinal fasciculus, and the corona radiata.

CONCLUSION

Diffusion differences were observed between the mildly impaired MS patients and control subjects. In addition, different diffusion measures correlated with PASAT scores for cognitive decline in parietal, frontal, as well as temporal white matter (WM) regions.

Magnetization transfer imaging in 'premanifest' Huntington's disease

To investigate whether magnetization transfer imaging (MTI) is a useful detector of diffuse brain abnormalities in ‘premanifest’ carriers of the Huntington’s disease (HD) gene mutation. Furthermore we examined the relations between MTI, clinical measures and CAG repeat length. Sixteen premanifest carriers of the HD gene without motor manifestation and 14 non-carriers underwent a clinical evaluation and a MRI scan. MTI analysis of whole brain, grey matter and white matter was performed producing magnetization transfer ratio (MTR) histograms. A lower peak height of the grey matter MTR histogram in carriers was significantly associated with more UHDRS motor abnormalities. Furthermore, a lower peak height of the whole brain, grey and white matter was strongly associated with a longer CAG repeat length. MTI measures themselves did not differ significantly between carriers and non-carriers. In premanifest HD mutation carriers, a lower MTR peak height, reflecting worse histological brain composition, was related to subtle motor abnormalities and higher CAG repeat length. Although we could not detect altered MTI characteristics in carriers of the HD gene mutation without clinical manifestations, we did provide evidence that the MTR peak height might reflect genetic and subclinical disease burden and may be of value in monitoring further disease progression and provide insight in clinical heterogeneity.

Magnetic resonance imaging as a potential surrogate for relapses in multiple sclerosis: a meta-analytic approach

OBJECTIVE

The aim of this work was to evaluate whether the treatment effects on magnetic resonance imaging (MRI) markers at the trial level were able to predict the treatment effects on relapse rate in relapsing-remitting multiple sclerosis.

METHODS

We used a pooled analysis of all the published randomized, placebo-controlled clinical trials in relapsing-remitting multiple sclerosis reporting data both on MRI variables and relapses. We extracted data on relapses and on MRI "active" lesions. A regression analysis weighted on trial size and duration was performed to study the relation between the treatment effect on relapses and the treatment effect on MRI lesions. We validated the estimated relation on an independent set of clinical trials satisfying the same inclusion criteria but with a control arm other than placebo.

RESULTS

A set of 23 randomized, double-blind, placebo-controlled trials in relapsing-remitting multiple sclerosis was identified, for a total of 63 arms, 40 contrasts, and 6,591 patients. A strong correlation was found between the effect on the relapses and the effect on MRI activity. The adjusted R(2) value of the weighted regression line was 0.81. The regression equation estimated using the placebo-controlled trials gave a satisfactory prediction of the treatment effect on relapses when applied to the validation set.

INTERPRETATION

More than 80% of the variance in the effect on relapses between trials is explained by the variance in MRI effects. Smaller and shorter phase II studies based on MRI lesion end points may give indications also on the effect of the treatment on relapse end points.

Reduced N-acetylaspartate is consistent with axonal dysfunction in cerebral small vessel disease

BACKGROUND

Cerebral small vessel disease (SVD) is an important cause of cognitive impairment, but the pathophysiological mechanisms remain unclear. We used (1)H MRS to investigate brain metabolic differences between patients with SVD and controls and correlated this with cognition.

METHODS

35 patients with SVD (lacunar stroke and radiological evidence of confluent leukoaraiosis) and 35 controls underwent multi-voxel spectroscopic imaging of white matter to obtain absolute metabolite concentrations of N-acetylaspartate (NAA), total creatines, total cholines, myo-inositol, and lactate. A range of cognitive tests was performed on patients with SVD, and composite scores were calculated.

RESULTS

Scans of sufficient quality for data analysis were available in 29 cases and 35 controls. NAA was significantly reduced in patients compared with controls (lower by 7.27%, P = 0.004). However, when lesion load within each individual voxel (mean 22% in SVD vs 5% in controls, P < 0.001) was added as a covariate, these differences were no longer significant, suggesting that the metabolite differences arose primarily from differences in lesioned tissue. In patients with SVD, there was no correlation between cognitive scores and any brain metabolite. No lactate, an indicator of anaerobic metabolism, was detected.

CONCLUSIONS

The most consistent change in SVD is a reduction in NAA, a marker of neuronal integrity. The lack of correlation with cognition does not support the use of MRS as a surrogate disease marker.

Quantitation of brain tissue changes associated with white matter hyperintensities by diffusion-weighted and magnetization transfer imaging: the LADIS (Leukoaraiosis and Disability in the Elderly) study

PURPOSE

To explore the value of diffusion-weighted imaging (DWI) and magnetization transfer imaging (MTI) for the improved detection and quantification of cerebral tissue changes associated with ageing and white matter hyperintensities (WMH).

MATERIALS AND METHODS

DWI (n = 340) and MTI (n = 177) were performed in nine centers of the multinational Leukoaraiosis And DISability (LADIS) study investigating the impact of WMH on 65- to 85-year-old individuals without prior disability. We assessed the apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) of normal appearing brain tissue (NABT) and within WMH and related them to subjects' age and WHM severity according to the Fazekas score.

RESULTS

ADC and MTR values showed a significant inter-site variation, which was stronger for the MTR. After z-transformation multiple regression analysis revealed WMH severity and age as significant predictors of global ADC and MTR changes. Only lesional ADC, but not MTR was related to WMH severity.

CONCLUSION

ADC and MTR are both sensitive for age and WMH related changes in NABT. The ADC is more sensitive for tissue changes within WMH and appears to be more robust for multicenter settings.

MR spectroscopy (MRS) and magnetisation transfer imaging (MTI), lesion load and clinical scores in early relapsing remitting multiple sclerosis: a combined cross-sectional and longitudinal study

The purpose of this study was to correlate magnetic resonance imaging (MRI)-based lesion load assessment with clinical disability in early relapsing remitting multiple sclerosis (RRMS). Seventeen untreated patients (ten women, seven men; mean age 33.0 +/- 7.9 years) with the initial diagnosis of RRMS were included for cross-sectional as well as longitudinal (24 months) clinical and MRI-based assessment in comparison with age-matched healthy controls. Conventional MR sequences, MR spectroscopy (MRS) and magnetisation transfer imaging (MTI) were performed at 1.5 T. Lesion number and volume, MRS and MTI measurements for lesions and normal appearing white matter (NAWM) were correlated to clinical scores [Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite (MSFC)] for monitoring disease course after treatment initiation (interferon beta-1a). MTI and MRS detected changes [magnetisation transfer ratio (MTR), N-acetylaspartate (NAA)/creatine ratio] in NAWM over time. EDSS and lesional MTR increases correlated throughout the disease course. Average MTR of NAWM raised during the study (p < 0.05) and correlated to the MSFC score (r = 0.476, p < 0.001). At study termination, NAA/creatine ratio of NAWM correlated to the MSFC score (p < 0.05). MTI and MRS were useful for initial disease assessment in NAWM. MTI and MRS correlated with clinical scores, indicating potential for monitoring the disease course and gaining new insights into treatment-related effects.

The use of MR imaging as an outcome measure in multiple sclerosis clinical trials

MR imaging is an integral part of multiple sclerosis (MS) clinical trials. It provides the primary efficacy outcome of preliminary proof-of-concept studies and important corroborating data as secondary and exploratory outcomes in pivotal trials. At all stages of drug development, MR imaging provides important information on the kinetics and magnitude of treatment effect and insight into potential mechanisms of action. Attention to issues in scan acquisition, quantitative image processing, and statistical analysis is critical to generate high-quality data. Although it is unlikely that one single outcome measure can capture all aspects of the MS disease process, there is potential for MR imaging outcomes to evaluate inflammatory and degenerative components within clinical trials.

Gender and sex hormones in multiple sclerosis pathology and therapy

Several lines of evidence indicate that gender affects the susceptibility and course of multiple sclerosis (MS) with a higher disease prevalence and overall better prognosis in women than men. This sex dimorphism may be explained by sex chromosome effects and effects of sex steroid hormones on the immune system, blood brain barrier or parenchymal central nervous system (CNS) cells. The well known improvement in disease during late pregnancy has also been linked to hormonal changes and has stimulated recent clinical studies to determine the efficacy of and tolerance to sex steroid therapeutic approaches. Both clinical and experimental studies indicate that sex steroid supplementation may be beneficial for MS. This could be related to anti-inflammatory actions on the immune system or CNS and to direct neuroprotective properties. Here, clinical and experimental data are reviewed with respect to the effects of sex hormones or gender in the pathology or therapy of MS or its rodent disease models. The different cellular targets as well as some molecular mechanisms likely involved are discussed.

Reproducibility over a 1-month period of 1H-MR spectroscopic imaging NAA/Cr ratios in clinically stable multiple sclerosis patients

N-acetylaspartate/creatine (NAA/Cr) ratios, assessed with proton magnetic resonance spectroscopy, are increasingly used as a surrogate marker for axonal dysfunction and degeneration in multiple sclerosis (MS). The purpose of this study was to test short-time reproducibility of NAA/Cr ratios in patients with clinically stable MS. In 35 MS patients we analysed NAA/Cr ratios obtained with ¹H-MR spectroscopic imaging at the centrum semiovale either with lateral ventricles partially included (group 1; n=15) or more cranially with no ventricles included (group 2; n=20). To test short-term reproducibility of the NAA/Cr measurements, patients were scanned twice 4 weeks apart. We determined mean NAA/Cr and Cho/Cr ratios of 12 grey matter and 24 white matter voxels. Mean NAA/Cr ratios of both the white and grey matter did not change after 4 weeks. Overall 4-week reproducibility of the NAA/Cr ratio, expressed as coefficient of variation, was 4.8% for grey matter and 3.5% for white matter. Reproducibility of cranial scanning of the ventricles was slightly better than with cerebrospinal fluid included. Our study shows good short-term reproducibility of NAA/Cr ratio measurements in the centrum semiovale, which supports the reliability of this technique for longitudinal studies.

Long and short echo time proton magnetic resonance spectroscopic imaging of the healthy aging brain

PURPOSE

To investigate the relationship between subject age and white matter brain metabolite concentrations and R(2) relaxation rates in a cross-sectional study of human brain.

MATERIALS AND METHODS

Long- and short-echo proton spectroscopic imaging were used to investigate concentrations and R2 relaxation rates of N-acetyl aspartate (NAA) + N-acetyl aspartyl glutamate (NAAG), choline (Cho), creatine (Cr), and myoinositol (mI) in the white matter of the centrum semiovale of 106 healthy volunteers aged 50-90 years; usable data were obtained from 79 subjects. A major aim was to identify which parameters were most sensitive to changes with age. Spectra were analyzed using the LCModel method.

RESULTS

The apparent R2 of NAA and the LCModel concentration of Cr at short echo time were significantly correlated with age after multiplicity correction. Large lipid resonances were observed in the brain midline of some subjects, the incidence increasing significantly with age. We believe this to result from lipid deposits in the falx cerebri.

CONCLUSION

Since only short-echo spectroscopy showed a robust relationship between Cr and subject age, and detects more metabolites than long echo time, we conclude that short-echo is superior to long-echo for future aging studies. Future studies could usefully determine whether the Cr-age relationship is due to changes in concentration, T1, or both.

Clinically benign multiple sclerosis despite large T2 lesion load: can we explain this paradox?

Magnetic resonance imaging (MRI) techniques such as magnetization transfer imaging and magnetic resonance spectroscopy (MRS) may reveal otherwise undetectable tissue damage in multiple sclerosis (MS) and can serve to explain more severe disability than expected from conventional MRI. That an inverse situation may exist where non-conventional quantitative MRI and MRS metrics would indicate less abnormality than expected from T2 lesion load to explain preserved clinical functioning was hypothesized. Quantitative MRI and MRS were obtained in 13 consecutive patients with clinically benign MS (BMS; mean age 44 +/- 9 years) despite large T 2 lesion load and in 15 patients with secondary progressive MS (SPMS; mean age 47 +/- 6 years) matched for disease duration. The magnetization transfer ratio (MTR), magnetization transfer rate (kfor), brain parenchymal fraction (BPF) and brain metabolite concentrations from proton MRS were determined. BMS patients were significantly less disabled than their SPMS counterparts (mean expanded disability status score: 2.1 +/- 1.1 versus 6.2 +/- 1.1; P < 0.001) and had an even somewhat higher mean T2 lesion load (41.2 +/- 27.1 versus 27.9 +/- 24.8 cm3; P = 0.19). Normal appearing brain tissue histogram metrics for MTR and kfor, mean MTR and kfor of MS lesions and mean BPF were similar in BMS and SPMS patients. Levels of N-acetyl-aspartate, choline and myoinositol were comparable between groups. This study thus failed to explain the preservation of function in our BMS patients with large T2 lesion load by a higher morphologic or metabolic integrity of the brain parenchyma. Functional compensation must come from other mechanisms such as brain plasticity.

Restless legs syndrome is a common finding in multiple sclerosis and correlates with cervical cord damage

In this prospective study, we estimated the prevalence of restless legs syndrome (RLS) in multiple sclerosis (MS) patients, and compared the extent of brain and cervical cord damage between patients with and without RLS using conventional and diffusion tensor magnetic resonance imaging (MRI). Eighty-two consecutive MS patients were evaluated. Each patient underwent a medical history interview, a neurological examination and brain/cervical cord MRI. Global and regional dual-echo lesion load (LL), number of cervical cord lesions, mean diffusivity (MD) and fractional anisotropy (FA) histograms metrics of the normal-appearing tissues of the brain and cervical cord were assessed. Thirty subjects had RLS; they showed a higher Expanded Disability Status Scale score than patients without. No difference between the two groups was found in whole brain, cerebellar and brainstem T(2)-LLs; MD and FA histograms derived metrics of the normal appearing brain tissues; basal ganglia MD; number of cervical cord lesions and cord MD histograms derived metrics. Cervical cord average FA was significantly reduced in MS patients with RLS compared to those without. RLS symptoms are very common in MS. This form of RLS should be considered as symptomatic. Higher disability and cervical cord damage represent a significant risk factor for RLS in MS patients.

Functional MRI in multiple sclerosis

There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not simply depend on the extent of tissue destruction, but rather represents a complex balance among tissue damage, tissue repair, and cortical reorganization. Functional magnetic resonance imaging (fMRI) provides information about the extent and nature of brain plasticity, which follows MS structural injury and might have the potential to limit the clinical manifestations of the disease. An altered recruitment of regions normally devoted to the performance of a given task and/or the recruitment of additional areas, which are not typically activated by healthy people for performing that given task, have been described in patients with MS, independent of their clinical phenotype when investigating the visual, cognitive, and motor systems. These functional changes have been related to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific central nervous system (CNS) structures, including the spinal cord and the optic nerve. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. An increased recruitment of the cerebral networks might represent a first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent "second-order" compensatory areas, and, on the other, contribute to the clinical manifestations of the disease.

Diffusion tensor MR imaging of the cervical spinal cord in patients with multiple sclerosis

Our purpose was to evaluate the ability of diffusion tensor imaging (DTI) to characterize cervical spinal cord white matter (WM) in patients with multiple sclerosis (MS). DTI were obtained in 21 MS patients and 21 control subjects (CS). Regions of interest (ROIs) were placed at C2/3, C3/4, and C4/5 within the right, left, and dorsal (WM) to calculate fractional anisotropy (FA) and the apparent diffusion coefficient (ADC). Measurements in plaques and normal-appearing white matter (NAWM) of MS patients were compared with mean FA and ADC of WM in CS. FA was significantly lower in all regions in MS patients than in CS. ADC was significantly higher in all regions in MS patients than in CS except for in the dorsal WM at C2/3 and the bilateral WM at C4/5. The mean FA was 0.441 for plaques and 0.542 for NAWM, as compared with 0.739 in CS. The mean ADC was 0.810 x 10(-3) mm(2)/s for plaques and 0.722 x 10(-3) mm(2)/s for NAWM, as compared with 0.640 x 10(-3) mm(2)/s for CS. FA and ADC showed significant differences between plaques, NAWM and control WM(P < 0.01).

The Role of Quantitative Neuroimaging Indices in the Differentiation of Ischemia From Demyelination: An Analytical Study With Case Presentation

BACKGROUND AND PURPOSE

Differentiation of acute and subacute ischemic stroke lesions from acute demyelinating lesions of multiple sclerosis (MS) may not be possible on conventional magnetic resonance imaging (MRI). Both lesion types enhance on T1 with gadolinium (Gd) contrast and both are hyperintense on diffusion-weighted imaging (DWI). This study is an analysis of two quantitative MR indices: (1) calculated apparent diffusion coefficients (ADCs) and (2) T2 relaxation times (T2R) as means toward differentiating acute ischemic lesions from acute demyelinating lesions. Chronic ischemic and demyelinating lesions were evaluated for comparison as well.

METHODS

The MRI of nine patients with both acute and chronic ischemic lesions and six patients with both acute and chronic demyelinating lesions were analyzed for ADC and T2Rs. The indices were measured by manually placing regions of interest (ROIs) at the anatomic center of the acute lesion. Acute ischemic lesions were chosen by their hyperintensity on DWI and hypointensity on ADC mapping. Acute demyelinating lesions were selected by peripheral contrast enhancement after the administration of Gd. Computation of the ADC involved the diffusion coefficient on a region by region basis as follows: D = -(b(0)/b(1000))ln(S(b1000)/S(b0)), where S(b1000) is the signal intensity on DWI and S(b0) is the signal intensity on T2 with diffusion sensitivities of b(0) and b(1000), respectively. Computation of the T2R was made as follows: T2R = (TE(T2)--TE(PD))/(ln SI(PD)--ln SI(T2)), where TE is the echo time of the different pulse sequences, SI is signal intensity on the different echo sequences, and PD represents proton density sequence.

RESULTS

Twenty-nine acute ischemia, 27 acute demyelination, 28 chronic ischemia, and 43 chronic demyelination image sets were analyzed. The differences between ADC(acute infarct) (0.760) versus ADC(acute plaque) (1.106) were significant (p < 0.02). The differences between T2R(acute infarct) (235.5) versus T2R(acute plaque) (170.5) were also significant (p < 0.02).

CONCLUSIONS

ADC in combination with T2R is a useful tool to differentiate acute ischemic from acute demyelinating lesions. The use of these neuroimaging indices along with magnetic resonance spectroscopy metabolite ratios is then demonstrated in elucidating the pathophysiological mechanism for a case of delayed posttraumatic bilateral internuclear ophthalmoplegia.

Diffusion tensor imaging of post mortem multiple sclerosis brain

Magnetic resonance imaging (MRI) is being used to probe the central nervous system (CNS) of patients with multiple sclerosis (MS), a chronic demyelinating disease. Conventional T₂-weighted MRI (cMRI) largely fails to predict the degree of patients' disability. This shortcoming may be due to poor specificity of cMRI for clinically relevant pathology. Diffusion tensor imaging (DTI) has shown promise to be more specific for MS pathology. In this study we investigated the association between histological indices of myelin content, axonal count and gliosis, and two measures of DTI (mean diffusivity [MD] and fractional anisotropy [FA]), in unfixed post mortem MS brain using a 1.5-T MR system. Both MD and FA were significantly lower in post mortem MS brain compared to published data acquired in vivo. However, the differences of MD and FA described in vivo between white matter lesions (WMLs) and normal-appearing white matter (NAWM) were retained in this study of post mortem brain: average MD in WMLs was 0.35 × 10^− 3 mm²/s (SD, 0.09) versus 0.22 (0.04) in NAWM; FA was 0.22 (0.06) in WMLs versus 0.38 (0.13) in NAWM. Correlations were detected between myelin content (Tr_myelin) and (i) FA (r = − 0.79, p < 0.001), (ii) MD (r = 0.68, p < 0.001), and (iii) axonal count (r = − 0.81, p < 0.001). Multiple regression suggested that these correlations largely explain the apparent association of axonal count with (i) FA (r = 0.70, p < 0.001) and (ii) MD (r = − 0.66, p < 0.001). In conclusion, this study suggests that FA and MD are affected by myelin content and – to a lesser degree – axonal count in post mortem MS brain.

Effects of glatiramer acetate and interferon-beta on neurodegeneration in a model of multiple sclerosis: a comparative study

Axonal destruction and neuronal loss occur early during multiple sclerosis (MS), an autoimmune inflammatory central nervous system disease that frequently manifests with acute optic neuritis. Glatiramer acetate (GA) and interferon-beta-1b (IFN-beta-1b) are two immunomodulatory agents that have been shown to decrease the frequency of MS relapses. However, the question of whether these substances can slow neurodegeneration in MS patients is the subject of controversy. In a rat model of experimental autoimmune encephalomyelitis, we investigated the effects of GA and IFN-beta-1b on the survival of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve. For each substance, therapy was started 14 days before immunization, on the day of immunization, or on the day of clinical disease onset. After myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis became clinically manifest, optic neuritis was monitored by recording visual evoked potentials. The function of RGCs was measured by electroretinograms. Although early GA or IFN-beta-1b treatment showed benefit on disease activity, only treatment with GA exerted protective effects on RGCs, as revealed by measuring neurodegeneration and neuronal function. Furthermore, we demonstrate that this GA-induced neuroprotection does not exclusively depend on the reduction of inflammatory infiltrates within the optic nerve.

Update on multiple sclerosis

In this article the basic features of the focal MR imaging lesions and the underlying pathology are reviewed. Next, the diffuse pathology in the normal-appearing white and gray matter as revealed by conventional and quantitative MR imaging techniques is discussed, including reference to how the focal and diffuse pathology may be in part linked through axonal-neuronal degeneration. The MR imaging criteria incorporated for the first time into formal clinical diagnostic criteria for multiple sclerosis are next discussed. Finally, a discussion is provided as to how MR imaging is used in monitoring subclinical disease either before or subsequent to initiation of treatment, in identifying aggressive subclinical disease, and in monitoring treatment.

EFNS guidelines on the use of neuroimaging in the management of multiple sclerosis

Magnetic resonance (MR)-based techniques are widely used for the assessment of patients with suspected and definite multiple sclerosis (MS). However, despite the publication of several position papers, which attempted to define the utility of MR techniques in the management of MS, their application in everyday clinical practice is still suboptimal. This is probably related, not only, to the fact that the majority of published guidelines focused on the optimization of MR technology in clinical trials, but also to the continuing development of modern, quantitative MR-based techniques, that have not as yet entered the clinical arena. The present report summarizes the conclusions of the 'EFNS Expert Panel of Neuroimaging of MS' on the application of conventional and non-conventional MR techniques to the clinical management of patients with MS. These guidelines are intended to assist in the use of conventional MRI for the diagnosis and longitudinal monitoring of patients with MS. In addition, they should provide a foundation for the development of more widespread but rational clinical applications of non-conventional MR-based techniques in studies of MS patients.

Imaging brain damage in first-degree relatives of sporadic and familial multiple sclerosis

OBJECTIVE

Our objective was to assess brain damage in first-degree relatives of patients with sporadic and familial multiple sclerosis (MS).

METHODS

Asymptomatic first-degree relatives of sporadic (sMS, n = 152) and familial MS (fMS, n = 88) and healthy volunteers (NC, n = 56) underwent brain MRI and magnetization transfer (MT) imaging on a mobile MR scan. On MR examinations, we visually assessed white matter (WM) lesions and quantified WM lesion volumes, brain volumes, and MT ratio (MTr) in lesions and normal-appearing WM (NAWM).

RESULTS

A lesional MR pattern similar to that of MS patients was found in 4% sMS and 10% fMS. In these WM lesions, MTr was lower (p < 0.0001) than in the WM of NC. In contrast, there was no difference in NAWM-MTr and brain volume values between the three groups.

INTERPRETATION

Focal brain abnormalities indistinguishable from those of MS occur in asymptomatic first-degree relatives of MS patients. These are twice more frequent in fMS than in sMS but do not lead to the widespread tissue damage commonly found in MS patients. Although there is a genetic susceptibility to develop brain abnormalities suggestive of focal demyelination in first-degree relatives of MS patients, other factors are probably critical for the development of a diffuse, clinically relevant, pathology.

Assessment of MRI abnormalities of the brainstem from patients with migraine and multiple sclerosis

BACKGROUND

In patients with migraine, functional changes have been described in the red nucleus (RN), substantia nigra (SN) and periaqueductal gray matter (PAG).

PURPOSE

To evaluate whether and at which frequency these structures are involved by MRI-detectable structural abnormalities in migraineurs and to investigate the pathogenic role of these abnormalities by assessing their frequency and extent in patients with multiple sclerosis (MS) and migraine.

METHODS

On brain dual-echo scans obtained from 58 migraineurs (40 without and 18 with aura), 37 MS patients with migraine without aura and 42 MS patients without migraine, the presence of hyperintense lesions involving the brainstem structures was recorded. A test of heterogeneity between groups was used to compare the presence of lesions among patient groups.

RESULTS

Lesions of RN, SN and PAG were found in all patient groups, with frequency from 57.5% to 86.5%. Significant between-group differences for all these regions were found. No difference was found between migraine patients with and without aura. Compared with MS patients without migraine, MS patients with migraine had more significant involvement of the SN (p=0.02) and RN (p<0.0001). Compared with migraine patients, MS patients with migraine had more significant involvement of the SN and PAG (p ranging from 0.009 to 0.02).

CONCLUSIONS

T2-visible lesions in the brainstem are frequent in patients with migraine, but do not seem to be associated with the presence of aura. Demyelinating lesions in the RN, SN and PAG might be among the factors responsible for the presence of migraine in patients with MS.

Fluoxetine increases cerebral white matter NAA/Cr ratio in patients with multiple sclerosis

Axonal degeneration in multiple sclerosis (MS) may be caused by mitochondrial dysfunction and is associated with decreased levels of N-acetylaspartate (NAA) as measured with 1H-magnetic resonance spectroscopy (MRS). Fluoxetine stimulates astrocytic glycogenolysis, which serves as an energy source for axons. Eleven patients with MS received fluoxetine orally 20 mg a day during the first week, and 40 mg a day during the second week. The mean NAA/Creatine ratio in cerebral white matter of the MS patients increased from 1.77 at baseline to 1.84 at the end of the second week (p=0.007). These findings show evidence for a reversible axonal dysfunction in patients with MS and provide a rationale for investigating whether fluoxetine has neuroprotective effects in MS.

MRI quantification of gray and white matter damage in patients with early–onset multiple sclerosis

BACKGROUND AND OBJECTIVE

Contrary to what happens in adult-onset multiple sclerosis (MS), in a previous preliminary magnetic resonance imaging (MRI) study we showed only subtle normal-appearing brain tissue changes in patients with earlyonset MS. Our objective was to evaluate the presence and extent of tissue damage in the brain normalappearing white matter (NAWM) and gray matter (GM) from a larger population of patients with earlyonset MS.

METHODS

Using diffusion tensor (DT) and magnetization transfer (MT) MRI, we obtained DT and MT ratio (MTR) maps of the NAWM and GM from 23 patients with early-onset MS and 16 sex- and age-matched healthy volunteers.

RESULTS

Compared with healthy volunteers, patients with early-onset MS had significantly increased average MD (p = 0.02) and FA peak height (p = 0.007) and decreased average FA (p <0.0001) of the NAWM. Brain dual-echo lesion load was significantly correlated with average FA (r = -0.48, p = 0.02) and with FA peak height (r = 0.45, p = 0.03) of the NAWM. No MTR and diffusion changes were detected in the GM.

CONCLUSIONS

This study confirms the paucity of the 'occult' brain tissue damage in patients with earlyonset MS. It also suggests that in these patients GM is spared by the disease process and that NAWM changes are likely to be secondary to Wallerian degeneration of fibers passing through macroscopic lesions.

Update on Multiple Sclerosis

In this article the basic features of the focal MR imaging lesions and the underlying pathology are reviewed. Next, the diffuse pathology in the normal-appearing white and gray matter as revealed by conventional and quantitative MR imaging techniques is discussed, including reference to how the focal and diffuse pathology may be in part linked through axonal-neuronal degeneration. The MR imaging criteria incorporated for the first time into formal clinical diagnostic criteria for multiple sclerosis are next discussed. Finally, a discussion is provided as to how MR imaging is used in monitoring subclinical disease either before or subsequent to initiation of treatment, in identifying aggressive subclinical disease, and treatment of nonresponders.

Functional magnetic resonance imaging and multiple sclerosis

There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not result simply from the extent of tissue destruction, rather it represents a complex balance between tissue damage, tissue repair and cortical reorganization. Functional magnetic resonance imaging provides information regarding the extent and nature of brain plasticity following MS-related structural injury, with the potential to limit the clinical manifestations of the disease. An altered recruitment of regions devoted normally to the performance of a given task and/or the recruitment of additional areas that are not typically activated by healthy people for performing that given task have been described in patients with MS, independent of their clinical phenotype, when investigating visual, cognitive and motor systems. These functional changes have been related not only to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific brain structures, but also to the degree of spinal cord and optic nerve involvement. It has also been suggested that an altered recruitment of specific brain regions might be associated with the appearance of clinical symptoms in MS, such as fatigue. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. More recently, in patients at the earliest clinical stage of the disease, it has been shown that such changes might contribute to predicting the evolution to definite MS, and it has been postulated that dynamic changes of brain cortical activations might occur with the progression of the disease. An increased recruitment of the cerebral networks might represent the first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent second-order compensatory areas, and on the other, contribute to the accumulation of irreversible disability.

Imaging the optic nerve in multiple sclerosis

Although multiple sclerosis (MS) frequently involves the optic nerves, imaging this structure is not yet performed routinely in clinical practice. The recent improvement of magnetic resonance (MR) technology and the development of new MR strategies, capable of providing an, in vivo, overall assessment of MS pathology has allowed objective metrics to be obtained for monitoring disease evolution, essentially in the brain. However, despite this progress, the correlation between brain MR metrics of the disease and clinical disability are still disappointing. An objective and accurate estimate of the presence and extent of optic nerve involvement might help to overcome this clinical/MRI paradox. This review summarizes the main results obtained from the application of conventional and modern MR-based techniques for the evaluation of optic nerve damage in MS.

Cortical adaptation in patients with MS: a cross-sectional functional MRI study of disease phenotypes

BACKGROUND

Movement-associated cortical reorganisation is known to occur in multiple sclerosis (MS). We aimed to define the development of such cortical reorganisation by comparing data from patients with different disease phenotypes.

METHODS

We studied patients with different phenotypes of MS: 16 patients with a clinically isolated syndrome (CIS), 14 patients with relapsing-remitting MS (RRMS) and no disability, 15 patients with RRMS and mild clinical disability, and 12 patients with secondary progressive MS (SPMS). Patients did a simple motor task with their unimpaired dominant hand during MRI, which was compared across the phenotype groups.

FINDINGS

Patients with a CIS activated more of the contralateral primary sensorimotor cortex than those with RRMS and no disability, whereas patients with RRMS and no disability activated more of the supplementary motor area than those with a CIS. Patients with RRMS and no disability activated more of the primary sensorimotor cortex, bilaterally, and more of the ipsilateral supplementary motor area than patients with RRMS and mild clinical disability. Conversely, patients with RRMS and mild clinical disability activated more of the contralateral secondary somatosensory cortex and inferior frontal gyrus, and the ipsilateral precuneus. Patients with RRMS and mild clinical disability activated more of the contralateral thalamus and of the ipsilateral secondary somatosensory cortex than those with SPMS. However, patients with SPMS activated more of the inferior frontal gyrus, bilaterally, the middle frontal gyrus, bilaterally, the contralateral precuneus, and the ipsilateral cingulate motor area and inferior parietal lobule.

INTERPRETATION

Movement-associated cortical reorganisation in patients with MS seems to vary across individuals at different stages of disease. Our study suggests that early in the disease course more areas typically devoted to motor tasks are recruited. Then bilateral activation of these regions is seen, and late in the disease course, areas that healthy people recruit to do novel or complex tasks are activated.

MRI in multiple sclerosis

MRI provides multiple uses and applications in multiple sclerosis(MS). The basic features of the MRI-detected lesions, including the underlying pathology, are discussed. MRI allows assessment of the normal-appearing white and gray matter, and neuronal tract and functional system disturbances. An overview of the clinical significance of these MRI measures is included, as a basis for understanding their role as outcome measures in clinical trials. MRI recently assumed greater importance in its role in establishing an earlier diagnosis of MS after a first clinical event, and in monitoring subclinical disease before or subsequent to the formal diagnosis. The background to these applications and practical issues are discussed.

Mean diffusivity and fractional anisotropy histogram analysis of the cervical cord in MS patients

The spinal cord is frequently involved in multiple sclerosis (MS), and cord damage may be an important contributor to disability. Diffusion tensor magnetic resonance imaging (DT-MRI) provides quantitative information about the structural and orientational features of the central nervous system. In order to assess whether diffusion tensor-derived measures of cord tissue damage are related to clinical disability, mean diffusivity (MD) and fractional anisotropy (FA) histograms from the cervical cord were acquired from a large cohort of MS patients. Diffusion-weighted sensitivity-encoded (SENSE) echo planar images of the cervical cord, and brain dual-echo and diffusion-weighted scans were acquired from 44 patients with MS and 17 healthy controls. Cord and brain MD and FA histograms were produced. An analysis of variance model, adjusting for cord volume and patient age, was used to compare cord DT-MRI parameters from controls and patients. A multivariate linear regression model was used to identify DT-MRI variables independently associated with disability. Average cervical cord FA was significantly lower in MS patients compared to controls. Cord cross-sectional area, average FA and average MD were all significantly correlated with the degree of disability (r values ranging from 0.36 to 0.51). The multivariate linear regression model retained average cord FA and average brain MD as variables independently associated with disability, with a correlation coefficient of 0.73 (P < 0.001). DT-MRI reveals a loss of cervical cord tissue structure in MS patients. The strong correlation found between a composite DT-MRI score and disability suggests that a full and accurate assessment of cervical cord damage in MS provides information that usefully contributes to an explanation of the clinical manifestations of the disease.

Overview of primary progressive multiple sclerosis (PPMS): similarities and differences from other forms of MS, diagnostic criteria, pros and cons of progressive diagnosis

Patients with the primary progressive form of multiple sclerosis (PPMS) have a unique clinical course and demonstrate additional demographic and imaging features, which separate them from the relapsing/remitting form of the condition. Whether these features indicate a fundamental difference in the underlying pathogenesis of the condition or simply reflect opposite ends of a clinical spectrum is unclear. What is clear, however, is that this form of MS provides a valuable model of progression, which has the potential to explain this most disabling component of the disease process. The lack of the hallmark relapses and remissions in PPMS poses diagnostic difficulties, some of which have been addressed by recently published diagnostic criteria. Following diagnosis, the need for information, specific to this form of MS, must be recognized and addressed.