Motor impairments and cognitive dysfunction are common in multiple sclerosis (MS). We aimed to delineate the relationship between cognitive capacity and upper and lower motor function in 211 MS patients, and 120 healthy volunteers. Lower and upper motor function were assessed with the Timed 25 Foot Walk (T25FW) and the Nine Hole Peg Test (NHPT) as implemented in the Multiple Sclerosis Functional Composite (MSFC). Subjects also underwent neuropsychological evaluation. Hierarchical linear regression analysis was conducted separately for the MS and healthy groups with the T25FW and NHPT serving as the outcome measures. Cognitive performance indices served as predictors. As expected, healthy subjects performed better than the MS group on all measures. Processing speed and executive function tests were significant predictors of lower and upper motor function in both groups. Correlations were more robust in the MS group, where cognitive tests predicted variability in motor function after controlling for disease duration and physical disability. In conclusion, we find evidence of higher order cognitive control of motor function that appears to be particularly salient in this large and representative MS sample. The findings may have implications for risk assessment and treatment of mobility dysfunction in MS.

Many studies have shown that multiple sclerosis (MS) has a significant impact on patient healthrelated quality of life (HRQOL), but the relative contributions of physical versus cognitive disability are not well established. Most studies have relied on HRQOL outcomes that depend largely on patient mood, life satisfaction, and personal happiness. The Sickness Impact Profile (SIP) is a measure of HRQOL known for its relatively strong emphasis on task completion and activities of daily living. As such, the SIP may be less influenced by depression. We sought to determine the relative influence of physical disability and cognition, above and beyond demographic and disease variables, in predicting HRQOL. Patients (n = 132) and healthy controls (n = 26) underwent complete neuropsychological evaluation using the Minimal Assessment of Cognitive Function in MS (MACFIMS) battery and a series of self-report measures assessing depression, fatigue, and HRQOL. The SIP was also administered. Correlation analysis and group comparisons revealed significant associations between cognition and HRQOL outcomes. Logistic regression models comparing the Expanded Disability Status Scale (EDSS) and cognitive tests in predicting poor physical HRQOL retained both EDSS and Symbol Digit Modalities Test (SDMT) performance, while models predicting poor psychosocial and poor overall HRQOL retained only the SDMT. These findings support cognition as a significant predictor of overall HRQOL, psychosocial HRQOL, and, interestingly, physical HRQOL. Int J MS Care. 2011;13:57-63.

low unitary conductance, a sub-conductance level and a long open/closed dwell time [1]. From the effect of non-electrolyte polymers on this unitary conductance we estimate a narrow pore with a diameter of ca. 2.2 Å [2]. This value is similar to that reported for the central pore in the structure of the PLN pentamer [3]. Hence the PLN pentamer, which is in equilibrium with the monomer[4], is the most likely channel forming structure. Moreover, recent data on selectivity show that the channel follows the II Eisenmann sequence (Rb>Cs>K>Na>Li). This pattern reveals that the ion selectivity is regulated by the radius of the binding site and not by the ionic radius. Our results combined with computational data suggest the presence of a selectivity filter in the pentamer PLN.