Chiu, Shannon

AbstractBackgroundDiffusion‐weighted magnetic resonance imaging (dMRI) examines tissue microstructure integrity in vivo. Prior dementia with Lewy bodies (DLB) diffusion tensor imaging studies yielded mixed results.ObjectiveWe employed free‐water (FW) imaging to assess DLB progression and correlate with clinical decline in DLB.MethodsBaseline and follow‐up MRIs were obtained at 12 and/or 24 months for 27 individuals with DLB or mild cognitive impairment with Lewy bodies (MCI‐LB). FW was analyzed using the Mayo Clinic Adult Lifespan Template. Primary outcomes were FW differences between baseline and 12 or 24 months. To compare FW change longitudinally, we included 20 cognitively unimpaired individuals from the Alzheimer's Disease Neuroimaging Initiative.ResultsWe followed 23 participants to 12 months and 16 participants to 24 months. Both groups had worsening in Montreal Cognitive Assessment (MoCA) and Movement Disorder Society‐Unified Parkinson's Disease Rating Scale (MDS‐UPDRS) scores. We found significant FW increases at both time points compared to baseline in the insula, amygdala, posterior cingulum, parahippocampal, entorhinal, supramarginal, fusiform, retrosplenial, and Rolandic operculum regions. At 24 months, we found more widespread microstructural changes in regions implicated in visuospatial processing, motor, and cholinergic functions. Between‐group analyses (DLB vs. controls) confirmed significant FW changes over 24 months in most of these regions. FW changes were associated with longitudinal worsening of MDS‐UPDRS and MoCA scores.ConclusionsFW increased in gray and white matter regions in DLB, likely due to neurodegenerative pathology associated with disease progression. FW change was associated with clinical decline. The findings support dMRI as a promising tool to track disease progression in DLB. © 2024 International Parkinson and Movement Disorder Society.

AbstractBackgroundDiffusion‐weighted MRI (dMRI) examines tissue microstructure integrity and white matter pathways in vivo. Prior dementia with Lewy bodies (DLB) studies focused on white matter or voxel‐based techniques. Less is known about longitudinal white and grey matter microstructural changes in DLB. We aimed to characterize longitudinal diffusion microstructural changes in individuals with DLB.MethoddMRI scans were collected on individuals with DLB from the Mayo Clinic Longitudinal Imaging Biomarkers of DLB Program. Demographics, clinical evaluations and MRI were collected at baseline, and 12‐ or 24‐months. Free water (FW) and FW‐corrected fractional anisotropy (FAT) were analyzed in grey and white matter using 122 bilateral template regions and tracts of interest from the Mayo Clinic Adult Lifespan Template. Primary outcomes were differences in FW and FAT between baseline and 12‐ or 24‐months.ResultWe identified 23 individuals with DLB or mild cognitive impairment with Lewy bodies (MCI‐LB) from baseline to 12‐months [mean age 69.3 years (SD 9.5); 95.8% male], and 16 individuals from baseline to 24‐months [mean age 67.5 years (SD 9.3); 100% male]. Participants at both time‐points showed worsening in Montreal Cognitive Assessment and Movement Disorders Society Unified Parkinson’s Disease Rating Scale motor scores (p<0.05). We found significant differences in FW, but not FAT, from baseline to 12‐months. Significant increases in FW at both time‐points compared to baseline were observed in the insula, putamen, parahippocampal, and rolandic operculum regions (pfdr<0.05). We found additional more widespread microstructural changes from baseline to 24‐months, with increased FW in the amygdala, entorhinal, mid and posterior cingulum, inferior frontal, hippocampal, pallidum, precuneus and retrosplenial regions (pfdr<0.05). We found decreased FAT from baseline to 24‐months in the cerebellar and superior occipital regions (pfdr<0.01).ConclusionLonger follow‐up at 24‐months identified broader networks of free water changes in individuals with DLB. Results support dMRI as a promising, non‐invasive tool to track disease progression in DLB. More investigation is needed to evaluate the relationship of microstructural changes with clinical progression in DLB.

Introduction: Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a multisystemic mitochondrial disorder that usually presents in childhood. Patients can have a wide array of neurological symptoms when presenting with stroke-like episodes, and imaging characteristics during the episodes can overlap with different neurological disorders. Case Report: A 61-year-old woman presented with communication difficulties consistent with auditory agnosia and was found to have bitemporal abnormalities on imaging that first raised the concern for herpes simplex virus encephalitis. Further work-up, in conjunction with the patient’s past medical and family history, suggested a mitochondrial disorder. Mitochondrial full genome analysis revealed m.3243A>G variant in the MT-TL1 gene, with 6% heteroplasmy in blood leading to a diagnosis of MELAS. Conclusions: MELAS is a disorder with clinical variability. Neuroimaging studies during stroke-like episodes in MELAS can provide significant clues to the underlying disorder. Although patients typically present in childhood, the first stroke-like episode can occur later in life in some patients, potentially related to a lower heteroplasmy level.