To investigate the correlation of callosal involvement and hemispheric disconnection in multiple sclerosis (MS), 20 patients with definite MS and sex, age and education matched 20 controls were given a standard, easy to use, but detailed neuropsychometric battary exploring interhemispheric transfer. Each subject also underwent a MRI scan to measure the midsagittal callosal area (MICA) and midline internal skull surface (MISS) for calculating a callosal atrophy index (MICA/MISS). Callosal lesion localization and the degree of white matter changes on MRI were also noted for the diseased patients. Test performance of the MS patients were statistically different from the control subjects (p<0.0001). Especially, tests on writing to dictation, cross-replication of hand postures and bimanuel motor coordination were found sensitive. Strikingly, callosal dysfunction was detected even without any visible corpus callosum lesion.
There was no correlation between the test performance and the callosal atrophy or white matter involvement.