Thalamic Iron Differentiates Primary-Progressive and Relapsing-Remitting Multiple Sclerosis.

Area of Science:

• Neurology
• Radiology
• Neuroimmunology

Background:

• Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system.
• Distinguishing between primary progressive MS (PPMS) and relapsing-remitting MS (RRMS) is crucial for treatment and prognosis.
• Previous studies have yielded controversial results regarding differences between MS subtypes.

Purpose of the Study:

• To investigate potential differences between PPMS and RRMS using conventional MRI parameters and iron deposit quantification.
• To explore the association between MRI findings, iron deposits, and clinical status (Expanded Disability Status Scale - EDSS) in MS subtypes.

Main Methods:

• 1.5T MRI scans were analyzed in 24 PPMS patients, 80 RRMS patients, and 20 healthy controls.
• Conventional quantitative MRI parameters included T2 lesion load, T1 lesion load, brain parenchymal fraction, and corpus callosum volume.
• Quantitative susceptibility mapping (QSM) was used to assess iron concentration in deep gray matter structures.

Main Results:

• The only significant MRI difference between PPMS and RRMS was decreased thalamic susceptibility in RRMS.
• In RRMS, EDSS scores positively correlated with white matter lesion load, brain atrophy, and iron in the putamen and caudate nucleus.
• In PPMS, EDSS scores showed a positive association with putaminal iron, but weaker than in RRMS.

Conclusions:

• Thalamic susceptibility may aid in differentiating between PPMS and RRMS.
• The distinct associations between EDSS and MRI/iron parameters in RRMS versus PPMS suggest different underlying mechanisms of disability progression.
• These findings highlight the potential of advanced MRI techniques in understanding MS heterogeneity.