Understanding multiple sclerosis as a disease spectrum: above and below the clinical threshold.

PURPOSE OF REVIEW: Research in multiple sclerosis (MS) has long been predicated on clinical groupings that do not reflect the underlying biologic heterogeneity apparent within patient populations. This review explicates the various levels of explanation through which the spectrum of disease is described and investigated both above and below the clinical threshold of detection, as framed by the topographical model of MS, to help advance a cogent mechanistic framework. RECENT FINDINGS: Contemporary evidence has amended the view of MS as consisting of sequential disease phases in favor of a spectrum of disease with an admixture of interdependent and dynamic pathobiological axes driving tissue injury and progression. Recent studies have shown the presence of acute and compartmentalized inflammation and mechanisms of neurodegeneration beginning early and evolving throughout the disease continuum. Still, the gap between the understanding of immunopathologic processes in MS and the tools used to measure relevant molecular, laboratory, radiologic, and clinical metrics needs attention to enable better prognostication of disease and monitoring for changes along specific pathologic axes and variable treatment outcomes. SUMMARY: Aligning on a consistently-applied mechanistic framework at distinct levels of explanation will enable greater precision across bench and clinical research, and inform discourse on drivers of disability progression and delivery of care for individuals with MS.

The impact of social distancing measures on anti-JC virus serostatus changes before and during the COVID-19 pandemic in US patients with multiple sclerosis.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic offered an epidemiological opportunity to evaluate if isolation and masking affected John Cunningham (JC) virus transmission. OBJECTIVE: This study aimed to assess the proportion of natalizumab-treated patients who converted to a positive anti-JCV antibody serostatus before and during the pandemic. METHODS: Data from TYSABRI Outreach: Unified Commitment to Health (TOUCH) for 22,375 US patients treated with natalizumab with anti-JCV antibody records were assessed in epochs annually from 2017 to 2022. RESULTS: Pre-pandemic anti-JCV antibody serostatus change was observed for 7.4%-7.7%. During the first and second years of the pandemic, 7.3% and 7.2% of patients' serostatus changed, respectively. CONCLUSION: The proportion of patients with anti-JCV antibody serostatus change did not significantly differ during the first 2 years of the pandemic compared with prior years. In contrast to seasonal influenza, masking and social distancing had no discernable effect on JCV serostatus change.

MS becomes a treatable disease: 30 years later.

30 years ago the first disease-modifying therapy for relapsing multiple sclerosis was approved for use in the United States and soon thereafter across the globe. Since then the field of MS therapeutics, and studies of immunopathogenesis and genetics, have advanced our understanding of the disease and raised the hope of better addressing the next challenges of treating progressive disease, enhancing repair of the damaged nervous system and, hopefully, of a cure. Thirty years into the MS treatment era, the field continues to debate fundamental aspects of MS, and there exists a widening chasm between the triumphs in relapsing disease and the desolation of MS progression, which remains the principal unmet need. In this Personal Viewpoint, we outline lessons learned from the first era of great therapeutic development, as we look to the future of MS research and therapeutics.

The impact of relapse definition and measures of durability on MS clinical trial outcomes.

BACKGROUND: Definitions of trial measures are consequential to accurately capturing outcomes and cross-trial comparability, particularly for derivative measures. OBJECTIVE: Using CombiRx, examine the impact of relapse definition on endpoints and evaluate the durability of progression measures in Relapsing Remitting Multiple Sclerosis (RRMS). METHODS: CombiRx relapse types were distinguished by the presence or timing of Expanded Disability Status Scale (EDSS) increase. Using the broadest definition of relapse, progression endpoints were assessed in patients without relapses on trial. Durability compared EDSS at study end and time of worsening. RESULTS: Broadening relapse definition to the most inclusive definition increased annualized relapse rate (ARR) threefold in all arms and decreased progression independent of relapse activity (PIRA), defined as 6-month confirmed disability worsening (6M CDW) without relapse, by 44%. Neither PIRA nor PIA (progression independent of any inflammatory activity) guaranteed durable worsening, with 43% and 40%, respectively, improving by end of study. Multivariate analysis showed two CDW events, not relapse, predicted durability among patients meeting 6M CDW. CONCLUSIONS: The stringency of relapse definition impacted absolute ARR and composite endpoints in RRMS. Despite the most generous relapse definition, 43% of patients meeting PIRA on trial did not have durable worsening suggesting that relapse definition and durability should be considered to avoid overestimating progression in RRMS trials.

Depression symptoms and cognition in multiple sclerosis: Longitudinal evidence of a specific link to executive control.

BACKGROUND: Depression symptoms are prevalent in multiple sclerosis (MS) and associated with poorer cognition in cross-sectional studies; it is unknown whether changes in depression symptoms track with cognitive changes longitudinally. OBJECTIVE: Investigate whether changes in depression symptoms correspond with cognitive changes over time in MS, and identify specific cognitive functions related to depression symptoms. METHOD: Persons with early relapse-onset MS (n = 165) completed a depression questionnaire (Beck Depression Inventory FastScreen) and tests of cognitive speed, executive control, and memory at baseline and 3-year follow-up. One-way ANOVAs assessed differences in cognitive change across participants with worsened, stable, or improved depression symptoms from baseline to year 3. RESULTS: Change in depression symptoms was related to change in executive control (p = 0.001, ηp2 = 0.08; worsened mood with worsened executive control; improved mood with improved executive control), even when adjusting for cognitive speed (p = 0.002, ηp2 = 0.08). There were no links to cognitive speed (p = 0.826) or memory (p = 0.243). Regarding individual depression symptoms, executive control was related to loss of pleasure and suicidal thoughts. CONCLUSIONS: Executive control tracks with depression symptoms, raising hope that management of mood may improve executive control. The specific link between executive control and anhedonia implicates dysfunctional reward processing as a key component of MS depression.

EDSS 0 is not normal: Multiple sclerosis disease burden below the clinical threshold.

Little to no above-threshold deficits may be evident in early multiple sclerosis (MS). The Expanded Disability Status Scale (EDSS) is a standard measure of neurologic function, with an EDSS score of 0 defined as "neurologically normal." The topographical model of MS proposes that sub-threshold disease is compensated for by functional reserve. In this short report, we found that physically high-challenge measures of balance and upper extremity coordination reveal sub-threshold deficits in patients with EDSS score of 0 compared with healthy controls. Challenge task performance was correlated with imaging markers of both lesional burden of disease and a volumetric measure of brain reserve.

Multiple sclerosis diagnosis: Knowledge gaps and opportunities for educational intervention in neurologists in the United States.

BACKGROUND: Few studies have addressed the results of educational efforts concerning proper use of McDonald criteria (MC) revisions outside multiple sclerosis (MS) subspecialty centers. Neurology residents and MS subspecialist neurologists demonstrated knowledge gaps for core elements of the MC in a recent prior study. OBJECTIVE: To assess comprehension and application of MC core elements by non-MS specialist neurologists in the United States who routinely diagnose MS. METHODS: Through a cross-sectional study design, a previously developed survey instrument was distributed online. RESULTS: A total of 222 neurologists completed the study survey. Syndromes atypical for MS were frequently incorrectly considered "typical" MS presentations. Fourteen percent correctly identified definitions of both "periventricular" and "juxtacortical" lesions and 2% correctly applied these terms to 9/9 images. Twenty-four percent correctly identified all four central nervous system (CNS) regions for satisfaction of magnetic resonance imaging (MRI) dissemination in space. In two presented cases, 61% and 71% correctly identified dissemination in time (DIT) was not fulfilled, and 85% and 86% subsequently accepted nonspecific historical symptoms without objective evidence for DIT fulfillment. CONCLUSION: The high rate of knowledge deficiencies and application errors of core elements of the MC demonstrated by participants in this study raise pressing questions concerning adequacy of dissemination and educational efforts upon publication of revisions to MC.

Cerebellar pathology and disability worsening in relapsing-remitting multiple sclerosis: A retrospective analysis from the CombiRx trial.

BACKGROUND AND PURPOSE: Cerebellar damage is a valuable predictor of disability, particularly in progressive multiple sclerosis. It is not clear if it could be an equally useful predictor of motor disability worsening in the relapsing-remitting phenotype. AIM: We aimed to determine whether cerebellar damage is an equally useful predictor of motor disability worsening in the relapsing-remitting phenotype. METHODS: Cerebellar lesion loads and volumes were estimated using baseline magnetic resonance imaging from the CombiRx trial (n = 838). The relationship between cerebellar damage and time to disability worsening (confirmed disability progression [CDP], timed 25-foot walk test [T25FWT] score worsening, nine-hole peg test [9HPT] score worsening) was tested in stagewise and stepwise Cox proportional hazards models, accounting for demographics and supratentorial damage. RESULTS: Shorter time to 9HPT score worsening was associated with higher baseline Expanded Disability Status Scale (EDSS) score (hazard ratio [HR] 1.408, p = 0.0042) and higher volume of supratentorial and cerebellar T2 lesions (HR 1.005 p = 0.0196 and HR 2.211, p = 0.0002, respectively). Shorter time to T25FWT score worsening was associated with higher baseline EDSS (HR 1.232, p = 0.0006). Shorter time to CDP was associated with older age (HR 1.026, p = 0.0010), lower baseline EDSS score (HR 0.428, p < 0.0001) and higher volume of supratentorial T2 lesions (HR 1.024, p < 0.0001). CONCLUSION: Among the explored outcomes, single time-point evaluation of cerebellar damage only allows the prediction of manual dexterity worsening. In clinical studies the selection of imaging biomarkers should be informed by the outcome of interest.

Phase 2 Trial of Ibudilast in Progressive Multiple Sclerosis.

BACKGROUND: There are limited treatments for progressive multiple sclerosis. Ibudilast inhibits several cyclic nucleotide phosphodiesterases, macrophage migration inhibitory factor, and toll-like receptor 4 and can cross the blood-brain barrier, with potential salutary effects in progressive multiple sclerosis. METHODS: We enrolled patients with primary or secondary progressive multiple sclerosis in a phase 2 randomized trial of oral ibudilast (≤100 mg daily) or placebo for 96 weeks. The primary efficacy end point was the rate of brain atrophy, as measured by the brain parenchymal fraction (brain size relative to the volume of the outer surface contour of the brain). Major secondary end points included the change in the pyramidal tracts on diffusion tensor imaging, the magnetization transfer ratio in normal-appearing brain tissue, the thickness of the retinal nerve-fiber layer, and cortical atrophy, all measures of tissue damage in multiple sclerosis. RESULTS: Of 255 patients who underwent randomization, 129 were assigned to ibudilast and 126 to placebo. A total of 53% of the patients in the ibudilast group and 52% of those in the placebo group had primary progressive disease; the others had secondary progressive disease. The rate of change in the brain parenchymal fraction was -0.0010 per year with ibudilast and -0.0019 per year with placebo (difference, 0.0009; 95% confidence interval, 0.00004 to 0.0017; P=0.04), which represents approximately 2.5 ml less brain-tissue loss with ibudilast over a period of 96 weeks. Adverse events with ibudilast included gastrointestinal symptoms, headache, and depression. CONCLUSIONS: In a phase 2 trial involving patients with progressive multiple sclerosis, ibudilast was associated with slower progression of brain atrophy than placebo but was associated with higher rates of gastrointestinal side effects, headache, and depression. (Funded by the National Institute of Neurological Disorders and Stroke and others; NN102/SPRINT-MS ClinicalTrials.gov number, NCT01982942 .).

Challenges in multiple sclerosis diagnosis: Misunderstanding and misapplication of the McDonald criteria.

OBJECTIVE: To assess comprehension and application of the McDonald criteria. BACKGROUND: Studies suggest that knowledge gaps for specific core elements of the McDonald criteria may contribute to multiple sclerosis (MS) misdiagnosis. METHODS: Neurology residents (NR) and multiple sclerosis specialists (MSS) in North America completed a web-based survey. RESULTS: A total of 160 participants were included: 72 NR and 88 MSS. Syndromes incorrectly identified as typical of MS included: complete transverse myelopathy (35% NR and 15% MSS), intractable vomiting/nausea/hiccoughs (20% NR and 5% MSS), and bilateral optic neuritis/unilateral optic neuritis with poor visual recovery (17% NR and 10% MSS). Periventricular magnetic resonance imaging (MRI) lesions were correctly identified by 39% NR and 52% MSS, and juxtacortical lesions were correctly identified by 28% NR and 53% MSS. The correct definition of "periventricular" was chosen by 38% NR and 61% MSS, and that of "juxtacortical" was chosen by 19% NR and 54% MSS. Regions incorrectly identified for MRI dissemination in space fulfillment included the optic nerve (31% NR and 26% MSS) and the subcortical white matter (11% NR and 18% MSS). The majority of participants assessed previous non-specific neurological symptoms without objective evidence of a central nervous system (CNS) lesion as sufficient for clinical dissemination in time. CONCLUSION: The McDonald criteria are often misunderstood and misapplied. Concerted educational efforts may prevent MS misdiagnosis.

Hippocampal volume is more related to patient-reported memory than objective memory performance in early multiple sclerosis.

BACKGROUND: When persons with multiple sclerosis (MS) report memory decline but objective memory performance is normal, there is a bias toward believing objective test results. OBJECTIVE: Investigate whether subjective memory decline or objective memory performance is more related to hippocampal and hippocampal subfield volumes in early MS. METHODS: Persons with early MS (n = 185; ⩽5.0 years diagnosed) completed a subjective memory questionnaire; an objective memory composite was derived from four memory tests. Total hippocampal and subfield volumes were derived from high-resolution 3.0 T magnetic resonance images (MRIs). Partial correlations assessed links between hippocampal volumes and both subjective and objective memory, controlling for age, sex, mood, and pre-morbid intelligence quotient (IQ). RESULTS: Lower total hippocampal and CA1 volumes were related to worse subjective memory but not objective memory (controlling for multiple comparisons). Correlations between subjective memory and both CA1 and subiculum were significantly stronger than were correlations between objective memory and these subfields. Patients in the worst tertile of subjective memory complaints (but not objective memory) had lower hippocampal volumes than 35 demographically similar healthy controls. CONCLUSION: Patient-report is inherently a longitudinal assessment of within-person memory change in everyday life, which may be more sensitive to subtle disease-related changes than cross-sectional objective tests. Findings align with the aging literature.

Depression and cognitive function in early multiple sclerosis: Multitasking is more sensitive than traditional assessments.

BACKGROUND: Persons with multiple sclerosis (MS) and depression symptoms report real-world cognitive difficulties that may be missed by laboratory cognitive tests. OBJECTIVE: To examine the relationship of depressive symptoms to cognitive monotasking versus multitasking in early MS. METHOD: Persons with early MS (n = 185; ⩽5 years diagnosed) reported mood, completed monotasking and multitasking cognitive tests, and received high-resolution 3.0 T magnetic resonance imaging (MRI). Partial correlations analyzed associations between mood and cognition, controlling for age, sex, estimated premorbid IQ, T2 lesion volume, and normalized gray matter volume. RESULTS: Depression symptoms were more related to worse cognitive multitasking (-0.353, p < 0.001) than monotasking (r = -0.189, p = 0.011). There was a significant albeit weaker link to cognitive efficiency composite score (r = -0.281, p < 0.001), but not composite memory (r = -0.036, p > 0.50). Findings were replicated with a second depression measure. Multitasking was worse in patients with at least mild depression than both patients with no/minimal depression and healthy controls. Multitasking was not related to mood in healthy controls. CONCLUSIONS: Depression symptoms are linked to cognitive multitasking in early MS; standard monotasking cognitive assessments appear less sensitive to depression-related cognition. Further investigation should determine directionality and mechanisms of this relationship, with the goal of enhancing treatment for cognitive dysfunction and depression in MS.

Psychological resilience is linked to motor strength and gait endurance in early multiple sclerosis.

BACKGROUND: Psychologically resilient persons persist despite obstacles and bounce back after adversity, leading to better outcomes in non-neurologic populations. It is unknown whether psychological resilience relates to objective functional outcomes in multiple sclerosis (MS). OBJECTIVE: To determine whether psychological resilience explains differential objective cognitive and motor functioning in persons with early MS. METHODS: Psychological resilience was assessed in 185 patients with early MS and 50 matched healthy controls with the Connors-Davidson Resilience Scale (CDRS-10). Subjects completed the MS Functional Composite (MSFC) and a comprehensive neurobehavioral evaluation. Correlations assessed links between CDRS-10 and MSFC, motor indices (Total, Fine Motor, Gross Motor), and cognitive indices (Total, Cognitive Efficiency, Memory). RESULTS: Higher CDRS-10 among patients was linked to better MSFC and motor outcomes (but not cognition), with the most robust relationships for gross motor function (grip strength, gait endurance). Findings were independent of mood and fatigue. CDRS-10 was unrelated to MS disease burden. CDRS-10 was also specifically linked to motor outcomes in healthy controls. CONCLUSION: Functional outcomes vary across persons with MS, even when disease burden and neurologic disability are low. These findings identify high psychological resilience as a non-disease-specific contributor to motor strength and endurance, which may explain differential outcomes across patients.

Dissociable cognitive patterns related to depression and anxiety in multiple sclerosis.

BACKGROUND: Individuals with multiple sclerosis (MS) frequently present with depression and anxiety, as well as cognitive impairment, challenging clinicians to disentangle interrelationships among these symptoms. OBJECTIVE: To identify cognitive functions associated with anxiety and depression in MS. METHODS: Mood and cognition were measured in 185 recently diagnosed patients (Reserve Against Disability in Early Multiple Sclerosis (RADIEMS) cohort), and an independent validation sample (MEM CONNECT cohort, n = 70). Partial correlations evaluated relationships of cognition to anxiety and depression controlling for age, sex, education, and premorbid verbal intelligence. RESULTS: In RADIEMS cohort, lower anxiety was associated with better nonverbal memory (rp = -0.220, p = 0.003) and lower depression to better attention/processing speed (rp = -0.241, p = 0.001). Consistently, in MEM CONNECT cohort, lower anxiety was associated with better nonverbal memory (rp = -0.271, p = 0.028) and lower depression to better attention/processing speed (rp = -0.367, p = 0.002). Relationships were unchanged after controlling for T2 lesion volume and fatigue. CONCLUSION: Consistent mood-cognition relationships were identified in two independent cohorts of MS patients, suggesting that cognitive correlates of anxiety and depression are separable. This dissociation may support more precise models to inform treatment development. Treatment of mood symptoms may mitigate effects on cognition and/or treatment of cognition may mitigate effects on mood.

Word-finding difficulty is a prevalent disease-related deficit in early multiple sclerosis.

BACKGROUND: Persons with multiple sclerosis (MS) commonly report word-finding difficulty clinically, yet this language deficit remains underexplored. OBJECTIVE: To investigate the prevalence and nature of word-finding difficulty in persons with early MS on three levels: patient report, cognitive substrates, and neuroimaging. METHODS: Two samples of early MS patients (n = 185 and n = 55; ⩽5 years diagnosed) and healthy controls (n = 50) reported frequency/severity of cognitive deficits and underwent objective assessment with tasks of rapid automatized naming (RAN), measuring lexical access speed, memory, word generation, and cognitive efficiency. High-resolution brain magnetic resonance imaging (MRI) derived measurements of regional cortical thickness, global and deep gray matter volume, and T2 lesion volume. Relationships among patient-reported word-finding difficulty, cognitive performance, and neural correlates were examined. RESULTS: Word-finding difficulty was the most common cognitive complaint of MS patients and the only complaint reported more by patients than healthy controls. Only RAN performance discriminated MS patients with subjective word-finding deficits from those without subjective complaints and from healthy controls. Thinner left parietal cortical gray matter independently predicted impaired RAN performance, driven primarily by the left precuneus. CONCLUSION: Three levels of evidence (patient-report, objective behavior, regional gray matter) support word-finding difficulty as a prevalent, measurable, disease-related deficit in early MS linked to left parietal cortical thinning.

Early complement genes are associated with visual system degeneration in multiple sclerosis.

Multiple sclerosis is a heterogeneous disease with an unpredictable course and a wide range of severity; some individuals rapidly progress to a disabled state whereas others experience only mild symptoms. Though genetic studies have identified variants that are associated with an increased risk of developing multiple sclerosis, no variants have been consistently associated with multiple sclerosis severity. In part, the lack of findings is related to inherent limitations of clinical rating scales; these scales are insensitive to early degenerative changes that underlie disease progression. Optical coherence tomography imaging of the retina and low-contrast letter acuity correlate with and predict clinical and imaging-based outcomes in multiple sclerosis. Therefore, they may serve as sensitive phenotypes to discover genetic predictors of disease course. We conducted a set of genome-wide association studies of longitudinal structural and functional visual pathway phenotypes in multiple sclerosis. First, we assessed genetic predictors of ganglion cell/inner plexiform layer atrophy in a discovery cohort of 374 patients with multiple sclerosis using mixed-effects models adjusting for age, sex, disease duration, optic neuritis and genetic ancestry and using a combination of single-variant and network-based analyses. For candidate variants identified in discovery, we conducted a similar set of analyses of ganglion cell/inner plexiform layer thinning in a replication cohort (n = 376). Second, we assessed genetic predictors of sustained loss of 5-letters in low-contrast letter acuity in discovery (n = 582) using multivariable-adjusted Cox proportional hazards models. We then evaluated candidate variants/pathways in a replication cohort. (n = 253). Results of both studies revealed novel subnetworks highly enriched for connected genes in early complement activation linked to measures of disease severity. Within these networks, C3 was the gene most strongly associated with ganglion cell/inner plexiform layer atrophy (P = 0.004) and C1QA and CR1 were top results in analysis of sustained low-contrast letter acuity loss. Namely, variant rs158772, linked to C1QA, and rs61822967, linked to CR1, were associated with 71% and 40% increases in risk of sustained LCLA loss, respectively, in meta-analysis pooling discovery and replication cohorts (rs158772: hazard ratio: 1.71; 95% confidence interval 1.30-2.25; P = 1.3 × 10-4; rs61822967: hazard ratio: 1.40; 95% confidence interval: 1.16-1.68; P = 4.1 × 10-4). In conclusion, early complement pathway gene variants were consistently associated with structural and functional measures of multiple sclerosis severity. These results from unbiased analyses are strongly supported by several prior reports that mechanistically implicated early complement factors in neurodegeneration.

Brain microstructural injury occurs in patients with RRMS despite 'no evidence of disease activity'.

OBJECTIVES: The accuracy of 'no evidence of disease activity' (NEDA) in predicting long-term clinical outcome in patients with relapsing remitting multiple sclerosis (RRMS) is unproven, and there is growing evidence that NEDA does not rule out disease worsening. We used diffusion tensor imaging (DTI) to investigate whether ongoing brain microstructural injury occurs in patients with RRMS meeting NEDA criteria. METHODS: We performed a retrospective study to identify patients with RRMS visiting our centre over a 3-month period who had undergone prior longitudinal DTI evaluation at our facility spanning ≥2 years. Patients meeting NEDA criteria throughout the evaluation period were included in the NEDA group, and those not meeting NEDA criteria were included in an 'evidence of disease activity' (EDA) group. Fractional anisotropy (FA) and mean diffusivity (MD) maps were created, and annual rates of change were calculated. RESULTS: We enrolled 85 patients, 39 meeting NEDA criteria. Both NEDA and EDA groups showed longitudinal DTI worsening. Yearly FA decrease was lower in the NEDA group (0.5%, p<0.0001) than in the EDA group (1.2%, p=0.003), while yearly MD increase was similar in both groups (0.8% for NEDA and EDA, both p<0.01). There was no statistical difference in deterioration within and outside of T2 lesions. DTI parameters correlated with disability scores and fatigue complaints. CONCLUSIONS: White matter microstructural deterioration occurs in patients with RRMS over short-term follow-up in patients with NEDA, providing further evidence of the limitations of conventional measures and arguing for DTI in monitoring of the disease process.

Baseline EDSS proportions in MS clinical trials affect the overall outcome and power: A cautionary note.

BACKGROUND: In randomized clinical trials, when treatments do not work equally effectively across stratifications of participants, observed event rates may differ from those hypothesized leading to deviations in estimated power. OBJECTIVES: To investigate the effect of distributions of baseline Expanded Disability Status Scale (EDSS) proportions in relapsing-remitting multiple sclerosis (RRMS) on the trial outcome, confirmed disability progression rate (CDPR), and power. METHODS: We reported CDPRs in the CombiRx trial by baseline EDSS and by groups (1st (0, 1), 2nd (1.5, 2), 3rd (2.5, 3), and 4th (⩾3.5)) and investigated the effect of different combinations of baseline EDSS proportions on the trial outcome and power. RESULTS: There were 244 (25.4%) participants in the 1st group, 368 (38.4%) in the 2nd group, 223 (23.3%) in the 3rd group, and 124 (12.9%) in the 4th group with CDPRs of 40.1%, 13.9%, 11.2%, and 16.9%, respectively. Both CDPR and power increased when the proportion of the 1st group increased in hypothetical trials with equal sample sizes in each arm, and a 10% increase in the 1st group led to a 5% increase in power. CONCLUSION: Various baseline EDSS proportions yielded different CDPRs and power, suggesting caution in interpretation of treatment effects across trials that enrolled participants with different proportions of baseline EDSS.

Retinal degeneration in primary-progressive multiple sclerosis: A role for cortical lesions?

BACKGROUND: Retinal atrophy in multiple sclerosis (MS) is secondary to optic nerve focal inflammation and to injury of the posterior visual pathway. OBJECTIVES: To investigate the contribution of cortical lesions (CLs) to retinal pathology in primary-progressive multiple sclerosis (PPMS). METHODS: We performed a cross-sectional evaluation of 25 patients and 20 controls, relating magnetic resonance imaging (MRI) metrics of visual pathway integrity with parameters derived from spectral-domain optical coherence tomography (peripapillary retinal nerve fiber layer (RNFL) thickness, ganglion cell + inner plexiform layer (GCIPL) thickness, and macular volume (MV)). RESULTS: Mean RNFL, GCIPL thickness, and MV were significantly reduced in patients compared to controls. MV and GCIPL thickness were significantly correlated with visual acuity. RNFL thinning was associated with thalamus and visual cortex volume (respectively, p = 0.01 and p < 0.05). In addition to thalamic volume, GCIPL thinning was associated with CLs and intracortical lesion number and volume, leucocortical lesion volume (all p ⩽ 0.05) while MV decrease was associated with CLs volume ( p = 0.05) and intracortical lesion number and volume ( p < 0.05). CONCLUSION: Our results suggest that RNFL thinning and GCIPL thinning/MV decrease may be explained by alternative mechanisms including retrograde trans-synaptic degeneration and/or a common pathophysiologic process affecting both the brain with CLs and the retina with neuronal loss.

Homing in on consciousness in the nervous system: An action-based synthesis.

What is the primary function of consciousness in the nervous system? The answer to this question remains enigmatic, not so much because of a lack of relevant data, but because of the lack of a conceptual framework with which to interpret the data. To this end, we have developed Passive Frame Theory, an internally coherent framework that, from an action-based perspective, synthesizes empirically supported hypotheses from diverse fields of investigation. The theory proposes that the primary function of consciousness is well-circumscribed, serving the somatic nervous system. For this system, consciousness serves as a frame that constrains and directs skeletal muscle output, thereby yielding adaptive behavior. The mechanism by which consciousness achieves this is more counterintuitive, passive, and "low level" than the kinds of functions that theorists have previously attributed to consciousness. Passive frame theory begins to illuminate (a) what consciousness contributes to nervous function, (b) how consciousness achieves this function, and (c) the neuroanatomical substrates of conscious processes. Our untraditional, action-based perspective focuses on olfaction instead of on vision and is descriptive (describing the products of nature as they evolved to be) rather than normative (construing processes in terms of how they should function). Passive frame theory begins to isolate the neuroanatomical, cognitive-mechanistic, and representational (e.g., conscious contents) processes associated with consciousness.