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Background <p>Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron degeneration and prominent extra-motor involvement. Impaired clearance of neurotoxic proteins has led to increasing interest in the brain glymphatic system; however, its in vivo associations with brain microstructure and clinical heterogeneity remain incompletely understood.</p> Methods <p>One hundred forty-six patients with ALS and 149 demographically matched healthy controls (HCs) underwent multimodal MRI and comprehensive clinical assessments. Putative glymphatic function was quantified using diffusion tensor imaging along perivascular space (DTI-ALPS). Extracellular free water fraction (FWF) and free-water-corrected fractional anisotropy (fwcFA) were derived to characterize extracellular fluid and white matter microstructure. Group differences were assessed using vertex-wise and voxel-wise analyses with correction for multiple comparisons. Associations among imaging metrics and clinical measures were evaluated using correlation and serial mediation analyses.</p> Results <p>Compared with HCs, patients with ALS exhibited significantly reduced DTI-ALPS index, widespread increases in cortical FWF, bidirectional alterations in white matter FWF, and extensive reductions in fwcFA across major white matter tracts. Reduced DTI-ALPS was associated with changes in extracellular free water and white matter microstructural integrity, whereas FWF and fwcFA measures were associated with functional, cognitive, and emotional outcomes. Mediation analyses identified significant indirect associations between DTI-ALPS and both functional and cognitive measures through a pathway involving cortical FWF, white matter FWF, and fwcFA, although direct associations were not observed.</p> Conclusions <p>These findings provide in vivo evidence that putative glymphatic dysfunction co-occurs with extracellular fluid alterations, white matter microstructural changes, and clinical impairment in ALS. Multi-compartment diffusion imaging may offer complementary markers for characterizing brain microstructure and its clinical relevance in ALS.</p>

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Putative glymphatic dysfunction links extracellular fluid dysregulation to white matter degeneration and clinical impairment in amyotrophic lateral sclerosis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月27日

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  • Xin Jin,
  • Yan Fu,
  • Ting Qiu,
  • Jianyu Li,
  • Huixiong Zhang,
  • Yifan Chen,
  • Kewei Chen,
  • Yuanchao Zhang,
  • Junling Wang,
  • Xiaoping Yi,
  • Lena Palaniyappan,
  • B. Blair Braden

摘要

Background

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron degeneration and prominent extra-motor involvement. Impaired clearance of neurotoxic proteins has led to increasing interest in the brain glymphatic system; however, its in vivo associations with brain microstructure and clinical heterogeneity remain incompletely understood.

Methods

One hundred forty-six patients with ALS and 149 demographically matched healthy controls (HCs) underwent multimodal MRI and comprehensive clinical assessments. Putative glymphatic function was quantified using diffusion tensor imaging along perivascular space (DTI-ALPS). Extracellular free water fraction (FWF) and free-water-corrected fractional anisotropy (fwcFA) were derived to characterize extracellular fluid and white matter microstructure. Group differences were assessed using vertex-wise and voxel-wise analyses with correction for multiple comparisons. Associations among imaging metrics and clinical measures were evaluated using correlation and serial mediation analyses.

Results

Compared with HCs, patients with ALS exhibited significantly reduced DTI-ALPS index, widespread increases in cortical FWF, bidirectional alterations in white matter FWF, and extensive reductions in fwcFA across major white matter tracts. Reduced DTI-ALPS was associated with changes in extracellular free water and white matter microstructural integrity, whereas FWF and fwcFA measures were associated with functional, cognitive, and emotional outcomes. Mediation analyses identified significant indirect associations between DTI-ALPS and both functional and cognitive measures through a pathway involving cortical FWF, white matter FWF, and fwcFA, although direct associations were not observed.

Conclusions

These findings provide in vivo evidence that putative glymphatic dysfunction co-occurs with extracellular fluid alterations, white matter microstructural changes, and clinical impairment in ALS. Multi-compartment diffusion imaging may offer complementary markers for characterizing brain microstructure and its clinical relevance in ALS.