A longitudinal study of callosal atrophy and interhemispheric dysfunction in relapsing-remitting multiple sclerosis.
OBJECTIVE
To determine if callosal atrophy and interhemispheric dysfunction can be detected in the early stages of relapsing-remitting multiple sclerosis (MS) and to evaluate their progression in relation to the disability and evolution of lesions seen on magnetic resonance imaging during a 5-year period.


METHODS
We compared 30 patients who had clinically definite early-onset replasing-remitting MS and mild disability with control subjects. Regional and segmental callosal size and extent of white matter abnormalities on magnetic resonance imaging, as well as performance on tasks exploring interhemispheric transfer of motor, auditory, and sensory information were assessed. Patients with MS were evaluated at baseline and after 5 years. Physical disability was determined at both times using the Expanded Disability Status Scale score.


RESULTS
Patients with MS were seen with significant callosal atrophy and functional impairment of interhemispheric transfer at baseline that worsened during the 5-year study. A significant correlation was found between the magnitude of disability and the severity of morphological and functional callosal involvement at baseline. This association persisted at year 5. Baseline clinical characteristics such as age and prestudy relapse rate were unrelated to callosal size or interhemispheric performance. However, the number of baseline T2-weighted lesions was correlated with callosal involvement and this relation persisted at year 5.


CONCLUSIONS
Patients who had relapsing-remitting MS in the early stages of the disease and mild disability had significant callosal involvement that progressed over time. The relationship between disability, T2-weighted lesions load, and degree of morphological and functional callosal impairment confirm the potential value of using callosal dysfunction as a surrogate marker of disease progression in MS.
Pelletier
J
J
Department of Neurology, CHU Timone, F-13385 Marseilles 5, France. jpelletier@ap-hm.fr
Suchet
L
L
Witjas
T
T
Habib
M
M
Guttmann
C R
CR
Salamon
G
G
Lyon-Caen
O
O
Chérif
A A
AA
D000328:Adult; D000367:Age Factors; D001284:Atrophy / Q000473:pathology; D003337:Corpus Callosum / Q000473:pathology* / Q000503:physiopathology*; D004007:Dichotic Listening Tests; D004185:Disability Evaluation; D018450:Disease Progression; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000175:diagnosis* / Q000503:physiopathology*; D009483:Neuropsychological Tests; D012720:Severity of Illness Index