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Fixel-Based Analysis of Pretreatment MRI Identifies White Matter Abnormalities in Pediatric Anti-NMDAR Encephalitis
Daniel Ackom1, Janine Taitt-Tap2, Scott A Beardsley1,2
1Joint Department of Biomedical Engineering, Marquette University and Medical College of Wisconsin, Milwaukee, WI, USA.
Abstract:
Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder in which conventional MRI often appears normal, leading to clinical-radiologic dissociation and hindering early diagnosis and monitoring. We retrospectively studied five pediatric patients with anti-NMDAR encephalitis and compared their pretreatment diffusion MRI to age- and sex-matched controls. Using fixel-based analysis (FBA), we quantified tract-specific white matter abnormalities at the individual level. All patients showed significantly reduced fiber density and cross-section, with patterns ranging from focal to widespread involvement. In two patients, FBA abnormalities corresponded to seizure lateralization on EEG despite normal MRI, emphasizing FBA's added value in detecting seizure-concordant injury. One patient, exhibiting the highest disease burden and marked CSF pleocytosis, demonstrated extensive white matter tract disruption. These findings indicate that FBA derived from pretreatment MRI can identify clinically significant white matter injury at disease onset in pediatric anti-NMDAR encephalitis. Future large-scale studies should explore its potential as an individualized biomarker, which may offer diagnostic and prognostic value beyond conventional imaging.
Insights
Fixel-based analysis (FBA) detects white matter abnormalities in pediatric anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis, even when conventional MRI is normal. This advanced MRI technique aids in diagnosing and monitoring this autoimmune brain disorder.
Area of Science:
- Neuroscience
- Radiology
- Immunology
Background:
- Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder.
- Conventional MRI often shows normal findings, causing clinical-radiologic dissociation and diagnostic delays.
Purpose of the Study:
- To investigate the utility of fixel-based analysis (FBA) in detecting white matter abnormalities in pediatric anti-NMDAR encephalitis.
- To compare pretreatment diffusion MRI findings using FBA with age- and sex-matched controls.
Main Methods:
- Retrospective study of five pediatric patients with anti-NMDAR encephalitis.
- Application of fixel-based analysis (FBA) to quantify tract-specific white matter abnormalities on diffusion MRI.
- Comparison with age- and sex-matched control subjects.
Main Results:
- All patients exhibited significantly reduced white matter fiber density and cross-section.
- FBA identified focal to widespread white matter involvement.
- In two patients, FBA findings correlated with EEG seizure lateralization, despite normal conventional MRI.
Conclusions:
- Fixel-based analysis (FBA) can identify significant white matter injury at disease onset in pediatric anti-NMDAR encephalitis.
- FBA may offer diagnostic and prognostic value beyond conventional imaging.
- Further research is warranted to explore FBA as an individualized biomarker.
