Voxel-based assessment of differences in damage and distribution of white matter lesions between patients with primary progressive and relapsing-remitting multiple sclerosis
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Updated: Jul 7, 2026
Comprehensive Autopsy Program for Individuals with Multiple Sclerosis
Published on: July 19, 2019
Carol Di Perri1, Marco Battaglini, Maria L Stromillo
1Neurology and Neurometabolic Unit, Department of Neurological and Behavioral Sciences, University of Siena, Viale Bracci 2, 53100 Siena, Italy.
Background:
Several studies have reported lower focal demyelination and inflammatory activity in primary progressive multiple sclerosis (PPMS) than in relapsing-remitting MS (RRMS). However, very little is known about possible differences in damage and distribution that may occur within lesions visible on magnetic resonance imaging in the 2 forms of the disease.
Objective:
To evaluate differences in spatial distribution and structural damage of focal demyelinating lesions in patients with PPMS and RRMS.
Design:
We acquired conventional magnetic resonance and magnetization transfer images in 24 PPMS and 36 RRMS patients (matched for sex, age, and disease duration) and 23 healthy sex- and age-matched controls. In each participant, we measured T2- and T1-weighted lesion volumes and magnetization transfer ratios in lesional and nonlesional brain tissues. The spatial distribution of focal demyelination was assessed using T2- and T1-weighted lesion probability maps in each patient group. Voxel-based procedures were performed.
Setting:
University hospital.
Results:
Patients with PPMS had greater disability than those with RRMS, with 70% of PPMS patients and 11% of RRMS patients having relevant motor symptoms. The T1- and T2-weighted lesion volumes were higher in PPMS than in RRMS patients (P < .001). T1- and T2-weighted lesion probability maps showed that the maximum probability for lesions was higher in PPMS (peak probability, 45% and 29%, respectively) than in RRMS (peak probability, 33% and 19%, respectively) patients and was localized in the corona radiata. Voxelwise analysis of lesional magnetization transfer ratios gave overlapping results.
Conclusions:
Differences in cerebral pathologic involvement exist between RRMS and PPMS and contribute to variations in clinical disability.
Insights
Primary progressive multiple sclerosis (PPMS) shows greater lesion volume and distinct spatial distribution compared to relapsing-remitting MS (RRMS). These differences in brain pathology correlate with increased clinical disability in PPMS patients.
Area of Science:
- Neuroimaging
- Neurology
- Multiple Sclerosis Pathophysiology
Background:
- Studies indicate less focal demyelination and inflammation in primary progressive multiple sclerosis (PPMS) versus relapsing-remitting multiple sclerosis (RRMS).
- Limited knowledge exists regarding differences in lesion damage and distribution between PPMS and RRMS.
Purpose of the Study:
- To compare the spatial distribution and structural damage of focal demyelinating lesions in PPMS and RRMS patients.
- To investigate MRI-based differences in lesion characteristics between the two major forms of multiple sclerosis.
Main Methods:
- Conventional MRI and magnetization transfer imaging were used in 24 PPMS, 36 RRMS patients, and 23 controls.
- T2- and T1-weighted lesion volumes and magnetization transfer ratios were measured.
- Spatial distribution was analyzed using lesion probability maps and voxel-based procedures.
Main Results:
- PPMS patients exhibited greater disability and higher T1- and T2-weighted lesion volumes than RRMS patients.
- Lesion probability maps revealed a higher peak probability in PPMS, predominantly in the corona radiata.
- Voxelwise analysis of lesional magnetization transfer ratios supported these findings.
Conclusions:
- Significant differences in cerebral pathological involvement are present between RRMS and PPMS.
- These pathological variations contribute to the observed differences in clinical disability between the two multiple sclerosis subtypes.
