A magnetization transfer histogram study of normal-appearing brain tissue in MS

Area of Science:

• Neuroimaging
• Quantitative MRI
• Multiple Sclerosis Pathophysiology

Background:

• Multiple sclerosis (MS) involves both macroscopic lesions and microscopic changes in normal-appearing brain tissue.
• Assessing these subtle changes is crucial for understanding disease progression and brain atrophy.

Purpose of the Study:

• To evaluate magnetization transfer ratio (MTR) histogram analysis for detecting changes outside MS lesions.
• To determine if these changes differ across MS clinical phenotypes (RRMS, PPMS, SPMS).
• To investigate the association between these microscopic changes, lesion load, and brain atrophy.

Main Methods:

• Brain MRI including dual-echo, T1-weighted, and MTR scans were acquired from 77 MS patients and 20 controls.
• MS lesions were segmented and excluded to create MTR histograms of normal-appearing tissue.
• MTR histogram parameters (average MTR, peak height, peak position), lesion load (T1, T2), and brain volume were analyzed.

Main Results:

• MTR histogram parameters were significantly lower in MS patients compared to controls, indicating microscopic changes.
• Patients with primary progressive MS (PPMS) and relapsing-remitting MS (RRMS) showed distinct histogram alterations.
• Microscopic changes (average histogram MTR) strongly correlated with macroscopic lesion load and brain volume.

Conclusions:

• MTR histogram analysis effectively detects microscopic white matter changes in MS.
• These changes represent a significant component of the overall disease burden and contribute to brain atrophy.
• Microscopic changes appear more pronounced in patients with secondary progressive MS (SPMS).