Cerebral disconnection in multiple sclerosis. Relationship to atrophy of the corpus callosum
S. M. Rao, L. Bernardin, G. J. Leo, L. Ellington, S. B. Ryan and L. S. Burg
Department of Neurology, Medical College of Wisconsin, Milwaukee 53226.
Left ear suppression to dichotically presented verbal stimuli has been
observed in patients with multiple sclerosis (MS). Rubens and coworkers
have suggested that a disconnection of the auditory callosal pathways may
account for this finding. To examine this proposal, we compared the
performance of 28 MS patients with significant corpus callosum atrophy
(CCA) on midsagittal magnetic resonance scans, 16 MS patients without
significant CCA, and 64 demographically matched normal control subjects on
two laterality tasks: verbal dichotic listening (consonant-vowel syllables)
and tachistiscopic object-naming latency. Results indicated that left ear
suppression was found only in the MS patients with CCA. Likewise, patients
in the MS group with CCA were slow in responding to stimuli presented in
the left visual field; this effect was not observed in patients without
CCA. These findings support the hypothesis that efficiency of
cross-callosal information flow is reduced in MS patients with CCA.
