Bergendal G, Martola J, Stawiarz L, Kristoffersen-Wiberg M, Fredrikson S, Almkvist O. Callosal atrophy in multiple sclerosis is related to cognitive speed. Acta Neurol Scand: 2013: 127: 281-289. (C) 2012 John Wiley & Sons A/S. Background Long-term changes regarding corpus callosum area (CCA) and information processing speed in cognitive and sensory-motor tasks have rarely been studied in multiple sclerosis (MS). Objective and methods Information processing speed in cognitive (Symbol Digit Modalities Test, SDMT), sensory (visual and auditory reaction time) and motor (finger-tapping speed, FT; right and left hand) tasks as well as auditory inter-hemispheric transfer (verbal dichotic listening, VDL) was related to CCA, measured by MRI at baseline and at follow-up after nine years in 22 patients with MS. Possible confounding by demographic (age, gender and education), clinical (symptom onset, duration, severity of disease) and relative brain volume (RBV) as well as T2 lesion load was taken into account. Results The smaller the CCA at baseline, the slower was SDMT performance at baseline. In a similar way, CCA at follow-up was associated with poor SDMT result at follow-up. Furthermore, the higher the annual rate of change in CCA, the poorer was performance in VDL on the left ear and the more pronounced was the right ear advantage. A positive relationship between performance in VDL right ear and annual rate of change in RBV was also seen. Sensory-motor tests were not significantly associated with CCA. T2 lesion load at baseline was associated with FT performance at baseline. Demographic, clinical and radiological (RBV and T2 lesion load) characteristics did not confound the significant relation between CCA and SDMT. Conclusions CCA unlike RBV and T2 lesion load was associated with SDMT, which indicated a marked cognitive rather than perceptual-motor component.