Decreasing brain iron in multiple sclerosis: The difference between concentration and content in iron MRI

Area of Science:

• Neuroimaging
• Neurodegenerative Diseases
• Iron Metabolism

Background:

• Elevated brain iron is observed in multiple sclerosis (MS) and other neurodegenerative diseases.
• The source of increased iron concentration (influx vs. relative tissue loss) in MS remains unclear.
• Understanding iron dynamics is crucial for diagnosing and monitoring neurodegeneration.

Purpose of the Study:

• To investigate longitudinal changes in deep gray matter (DGM) iron content in MS patients.
• To differentiate between iron influx and tissue atrophy as causes of altered iron concentration in MS.
• To correlate changes in DGM iron content with disease progression and disability.

Main Methods:

• Structural MRI and quantitative susceptibility mapping (QSM) were used to measure iron content.
• 120 MS patients and 40 healthy controls underwent assessments at baseline and after 2 years.
• Iron content was quantified in the thalamus, caudate, putamen, and globus pallidus.

Main Results:

• MS patients exhibited significantly lower thalamic iron content compared to controls.
• Progressive MS patients showed lower iron content than relapsing-remitting MS patients.
• DGM iron content decreased in MS patients over 2 years, while it remained stable or increased in controls.
• Decreasing thalamic iron content correlated with increased disability in MS patients.
• Observed increases in magnetic susceptibility in MS may be attributed to atrophy, not iron influx.

Conclusions:

• Disease-related atrophy, not iron influx, may explain temporal changes in magnetic susceptibility in MS.
• Declining DGM iron content in MS patients suggests iron removal from the brain.
• Longitudinal iron content changes in the thalamus are associated with disability progression in MS.