Relation of Cognition to Cerebellar Function in Multiple Sclerosis

Cerebellar signs and cognitive dysfunction often occur in parallel in Relapsing-Remitting Multiple Sclerosis (RR-MS). Motor planning is thought to be one area of cognition susceptible to damage but also a surrogate of cerebellar integrity. Therefore, the objective was to investigate the longitudinal relation of cognition to cerebellar function in RR-MS and how changes relate to motor planning and function.
A total of 11 RR-MS patients with cerebellar symptomatology (RR-MSc: 5 males, x̅ age: 41), 17 RR-MS patients without cerebellar symptomatology (RR-MSnc: 2 males, x̅ age: 40.94) and 9 matched control participants (HC: 2 males, x̅ age: 37.78) completed the Brief International Cognitive Assessment for MS (BICAMS), the Nine-hole Peg Test (NHPT) and the Grooved Pegboard Test (GPT) at baseline and at 12 months. The GPT - NHPT difference was used to compute a Motor Planning index (MPI), the NHPT serving as a control for sensorimotor impairment.
Mixed ANOVA revealed a consistent significant group separation on all cognitive and motor tests other than visual memory that was maintained over the follow-up period. There was a significant effect of time for the visual and verbal memory suggestive of learning. There were no significant interactions between group and time. Post hoc tests showed the RR-MSc group was significantly outperformed in tests of cognition, motor function and motor planning by both RR-MSc and HC. There was a significant correlation between measures of information processing speed and MPI.
RR-MSc were characterised by greater impairment on tests of cognition, motor function and motor planning than the RR-MSc. These differences were maintained over a year. The association of the MPI and SDMT indicates information processing speed may act as a moderator of motor planning. The next step is to validate the MPI with an MRI study exploring how it relates to cerebellar lesion load and atrophy.