Publications by authors named "Sridar Narayanan"

Demyelination disrupts the transmission of electrical signals in the brain and affects neurodevelopment in children with disorders such as multiple sclerosis and myelin oligodendrocyte glycoprotein-associated disorders. Although cognitive impairments are prevalent in these conditions, some children maintain cognitive function despite substantial structural injury. These findings raise an important question: in addition to the degenerative process, do compensatory neural mechanisms exist to mitigate the effects of myelin loss? We propose that a multi-dimensional approach integrating multiple neuroimaging modalities, including diffusion tensor imaging, magnetoencephalography and eye-tracking, is key to investigating this question.

View Article and Find Full Text PDF

The use of ultra-high-field 7-Tesla (7T) MRI in multiple sclerosis (MS) research has grown significantly over the past two decades. With recent regulatory approvals of 7T scanners for clinical use in 2017 and 2020, the use of this technology for routine care is poised to continue to increase in the coming years. In this context, the North American Imaging in MS Cooperative (NAIMS) convened a workshop in February 2023 to review the previous and current use of 7T technology for MS research and potential future research and clinical applications.

View Article and Find Full Text PDF

Slowly expanding lesions (SELs) in adults with multiple sclerosis (MS) indicate a progressive pathological process. Whether SELs are present in pediatric-onset MS (POMS) or myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is unknown. We studied 19 children with POMS and 14 with MOGAD (median age 14.

View Article and Find Full Text PDF

Background: Multiple sclerosis (MS) paramagnetic rim lesions (PRLs) are markers of chronic active biology and exhibit complex iron and myelin changes that may complicate quantification when using conventional MRI approaches.

Purpose: To conduct a multiparametric MRI analysis of PRLs.

Study Type: Retrospective/longitudinal.

View Article and Find Full Text PDF

Although 7 T MRI research has contributed much to our understanding of multiple sclerosis (MS) pathology, most prior data has come from small, single-center studies with varying methods. In order to truly know if such findings have widespread applicability, multicenter methods and studies are needed. To address this, members of the North American Imaging in MS (NAIMS) Cooperative worked together to create a multicenter collaborative study of 7 T MRI in MS.

View Article and Find Full Text PDF
Article Synopsis
  • In multiple sclerosis clinical trials, standard MRI measures often overlook specific regional effects, prompting the need for a more targeted analysis approach.
  • Researchers developed a technique using independent component analysis to assess co-varying grey matter volumes in individual MRI scans, allowing for better understanding of treatment and disability progression.
  • The study, analyzing data from over 5,000 participants across various MS types, identified 17 distinct patterns of regional volume loss, highlighting faster deterioration in certain networks among secondary progressive MS patients compared to those with relapsing-remitting forms.
View Article and Find Full Text PDF

Cortical lesions are common in multiple sclerosis and are associated with disability and progressive disease. We asked whether cortical lesions continue to form in people with stable white matter lesions and whether the association of cortical lesions with worsening disability relates to pre-existing or new cortical lesions. Fifty adults with multiple sclerosis and no new white matter lesions in the year prior to enrolment (33 relapsing-remitting and 17 progressive) and a comparison group of nine adults who had formed at least one new white matter lesion in the year prior to enrolment (active relapsing-remitting) were evaluated annually with 7 tesla (T) brain MRI and 3T brain and spine MRI for 2 years, with clinical assessments for 3 years.

View Article and Find Full Text PDF

Background: The phenomenon of pseudoatropy after initiation of anti-inflammatory therapy is believed to be reversible, but a rebound in brain volume following cessation of highly-effective therapy has not been reported.

Objectives: To evaluate brain volume change in a treatment interruption study (RESTORE) in which relapsing-remitting multiple sclerosis (RRMS) patients were randomized to switch from natalizumab to placebo, from natalizumab to once-monthly intravenous methylprednisolone (IVMP), or to remain on natalizumab.

Methods: T2 lesion volume (T2LV), baseline normalized brain volumes, and follow-up percent brain volume changes (PBVC) were calculated.

View Article and Find Full Text PDF

Background And Objectives: Cortical lesions (CL) are common in multiple sclerosis (MS) and associate with disability and progressive disease. We asked whether CL continue to form in people with stable white matter lesions (WML) and whether the association of CL with worsening disability relates to pre-existing or new CL.

Methods: A cohort of adults with MS were evaluated annually with 7 tesla (T) brain magnetic resonance imaging (MRI) and 3T brain and spine MRI for 2 years, and clinical assessments for 3 years.

View Article and Find Full Text PDF

Aging is characterized by a gradual decline of the body's biological functions, which can lead to increased production of reactive oxygen species (ROS). Antioxidants neutralize ROS and maintain balance between oxidation and reduction. If ROS production exceeds the ability of antioxidant systems to neutralize, a damaging state of oxidative stress (OS) may exist.

View Article and Find Full Text PDF

Background: Network-based measures are emerging MRI markers in multiple sclerosis (MS). We aimed to identify networks of white (WM) and grey matter (GM) damage that predict disability progression and cognitive worsening using data-driven methods.

Methods: We analysed data from 1836 participants with different MS phenotypes (843 in a discovery cohort and 842 in a replication cohort).

View Article and Find Full Text PDF
Article Synopsis
  • The study investigates how pediatric MOG antibody-associated disease (MOGAD) affects brain growth in children compared to healthy peers and those with MS or monophasic demyelination, highlighting the possible impact on brain maturation.* -
  • Researchers included children diagnosed with MOGAD, MS, or monophasic demyelination from a longitudinal study and used brain MRI scans to analyze regional brain volumes against normative data from healthy children.* -
  • Findings revealed that children with MOGAD show significant delays in expected brain growth, particularly in areas like the thalamus and caudate, indicating a deviation from typical brain development patterns.*
View Article and Find Full Text PDF

Background: The presence of subclinical optic nerve (ON) injury in youth living with pediatric-onset MS has not been fully elucidated. Magnetization transfer saturation (MTsat) is an advanced magnetic resonance imaging (MRI) parameter sensitive to myelin density and microstructural integrity, which can be applied to the study of the ON.

Objective: The objective of this study was to investigate the presence of subclinical ON abnormalities in pediatric-onset MS by means of magnetization transfer saturation and evaluate their association with other structural and functional parameters of visual pathway integrity.

View Article and Find Full Text PDF

Background: Parkinson's disease (PD) demonstrates neurodegenerative changes in the substantia nigra pars compacta (SNc) using neuromelanin-sensitive (NM)-MRI. As SNc manual segmentation is prone to substantial inter-individual variability across raters, development of a robust automatic segmentation framework is necessary to facilitate nigral neuromelanin quantification. Artificial intelligence (AI) is gaining traction in the neuroimaging community for automated brain region segmentation tasks using MRI.

View Article and Find Full Text PDF

Background: The use of advanced magnetic resonance imaging (MRI) techniques in MS research has led to new insights in lesion evolution and disease outcomes. It has not yet been determined if, or how, pre-lesional abnormalities in normal-appearing white matter (NAWM) relate to the long-term evolution of new lesions.

Objective: To investigate the relationship between abnormalities in MRI measures of axonal and myelin volume fractions (AVF and MVF) in NAWM preceding development of black-hole (BH) and non-BH lesions in people with MS.

View Article and Find Full Text PDF

The impact of multiple sclerosis (MS) and myelin oligodendrocyte glycoprotein (MOG) - associated disorders (MOGAD) on brain structure in youth remains poorly understood. Reductions in cortical mantle thickness on structural MRI and abnormal diffusion-based white matter metrics (e.g.

View Article and Find Full Text PDF

Background: Dramatic improvements in visualization of cortical (especially subpial) multiple sclerosis (MS) lesions allow assessment of impact on clinical course.

Objective: Characterize cortical lesions by 7 tesla (T) T-/T-weighted magnetic resonance imaging (MRI); determine relationship with other MS pathology and contribution to disability.

Methods: Sixty-four adults with MS (45 relapsing-remitting/19 progressive) underwent 3 T brain/spine MRI, 7 T brain MRI, and clinical testing.

View Article and Find Full Text PDF

Diffusely abnormal white matter, characterised by biochemical changes of myelin in the absence of frank demyelination, has been associated with clinical progression in secondary progressive multiple sclerosis. However, little is known about changes of diffusely abnormal white matter over time and their relation to focal white matter lesions. The objectives of this work were: (i) to characterize the longitudinal evolution of focal white matter lesions, diffusely abnormal white matter and diffusely abnormal white matter that transforms into focal white matter lesions; and (ii) to determine whether gadolinium enhancement, known to be associated with the development of new focal white matter lesions, is also related to diffusely abnormal white matter voxels that transform into focal white matter lesions.

View Article and Find Full Text PDF

Long-term cognitive deficits have been observed in some children who experience an acquired demyelinating syndrome (ADS). We examined changes in cognitive functioning over the first two years following incident ADS andtested whether normalized brain and thalamic volume accounted for decline over time. Twenty-five youth (mean age 12.

View Article and Find Full Text PDF

Background: Wave-CAIPI Visualization of Short Transverse relaxation time component (ViSTa) is a recently developed, short-T-sensitized MRI method for fast quantification of myelin water fraction (MWF) in the human brain. It represents a promising technique for the evaluation of subtle, early signals of demyelination in the cerebral white matter of multiple sclerosis (MS) patients. Currently however, few studies exist that robustly assess the utility of ViSTa MWF measures of myelin compared to more conventional MRI measures of myelin in the brain of MS patients.

View Article and Find Full Text PDF
Article Synopsis
  • Brain volume loss (BVL) is prevalent after high-dose immunosuppression treatment in multiple sclerosis patients, particularly affecting whole-brain, grey matter, and white matter volumes.
  • A study involving 24 relapsing-remitting MS patients measured brain volume changes over five years, revealing accelerated short-term BVL immediately after treatment, with varying rates of loss in different brain tissue types.
  • Key findings indicated that patients with gadolinium-enhancing lesions at baseline experienced significantly greater short-term BVL, while long-term rates stabilized and were similar among those who maintained event-free survival.
View Article and Find Full Text PDF

Objective: In multiple sclerosis (MS), MRI measures at the whole brain or regional level are only modestly associated with disability, while network-based measures are emerging as promising prognostic markers. We sought to demonstrate whether data-driven patterns of covarying regional grey matter (GM) volumes predict future disability in secondary progressive MS (SPMS).

Methods: We used cross-sectional structural MRI, and baseline and longitudinal data of Expanded Disability Status Scale, Nine-Hole Peg Test (9HPT) and Symbol Digit Modalities Test (SDMT), from a clinical trial in 988 people with SPMS.

View Article and Find Full Text PDF

Multiple sclerosis (MS) can be divided into four phenotypes based on clinical evolution. The pathophysiological boundaries of these phenotypes are unclear, limiting treatment stratification. Machine learning can identify groups with similar features using multidimensional data.

View Article and Find Full Text PDF