Voxel-Based (1) Assessment of Differences in Damage and Distribution of White Matter Lesions Between Patients With Primary Progressive and Relapsing-Remitting Multiple Sclerosis

Background 

Several studies have reported lower focal demyelinationand inflammatory activity in primary progressive multiple sclerosis(PPMS) than in relapsing-remitting MS (RRMS).  However, verylittle is known about possible differences in damage and distributionthat may occur within lesions visible on magnetic resonanceimaging in the 2 forms of the disease.

Objective 

To evaluate differences in spatial distributionand structural damage of focal demyelinating lesions in patientswith PPMS and RRMS.

Design 

­       We acquired conventional magnetic resonance andmagnetization transfer images in

­       24 PPMS and

­       36 RRMS patients

­       (matched for sex, age, and disease duration) and

­       23 healthysex- and age-matched controls.

In each participant, we measuredT2- and T1-weighted lesion volumes and magnetization transferratios in lesional and nonlesional brain tissues.  The spatialdistribution of focal demyelination was assessed using T2- andT1-weighted lesion probability maps in each patient group.  Voxel-basedprocedures were performed.

Setting 

University hospital.

Results 

Patients with PPMS had greater disability thanthose with RRMS, with

­       70% of PPMS patients and

­       11% of RRMSpatients

having relevant motor symptoms.  The T1- and T2-weightedlesion volumes were higher in PPMS than in RRMS patients (P < .001).  T1- and T2-weighted lesion probability maps showed that themaximum 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 thecorona radiata.  Voxelwise analysis of lesional magnetizationtransfer ratios gave overlapping results.

Conclusions 

Differences in cerebral pathologic involvementexist between RRMS and PPMS and contribute to variations inclinical disability.

Author Affiliations:

­       Department of Neurological and Behavioral Sciences,

o       University of Siena, Siena,

o       Italy (Drs Di Perri, Stromillo, Federico, and De Stefano, and Mr Battaglini); and

­       the Neurology Unit,

o       Hospital of Empoli, Empoli,

o       Italy (Drs Bartolozzi and Guidi).