Cognition and the cerebellum in multiple sclerosis

Cerebellar symptoms are associated with poor prognosis in MS. A small number of studies have reported a specific cognitive profile associated with cerebellar damage, including reduced information processing speed, impairments in visuospatial functions and verbal fluency deficits. The cerebellum is thought to encode models of sensory information, providing mental representations of the world used to plan motor actions. Motor planning may be a key factor in the disability that cerebellar involvement imposes. This study explores how the cognitive profile of those with MS with cerebellar symptoms (RR-MSc) relates to motor planning and motor function, and how this differs from those with MS without cerebellar symptoms (RR-MSnc) and healthy controls (HC).

Participants were assigned to three groups: HC (n = 21), RR-MSnc (n = 21) and RR-MSc (n = 14) using a validated self-report cerebellar symptom questionnaire (NARCOMS-TACS). Participants completed a cognitive test battery: BICAMS (CVLT-II, SDMT, BVMT-R), WLG, PASAT3 and TOPF. For assessment of motor functioning and motor planning, participants completed the 9-hole peg test (9HPT) as a sensorimotor control, and grooved pegboard test (GPT) which has greater motor planning demands. Subtraction of 9HPT from GPT was used to compute a motor planning index (MPI).

One-way ANCOVAs demonstrated significant differences between groups on all cognitive tests other than WLG. Post-hoc tests showed significant differences between RR-MSc and HC on all tests except WLG, and RR-MSc and RR-MSnc on SDMT, CVLT-II and PASAT3. On 9HPT, GPT and MPI, HC performed significantly better than both MS groups, and the RR-MSnc performed significantly better than RR-MSc. There were significant correlations between neuropsychological variables (other than WLG) and MPI.

RR-MSc showed greater impairment than RR-MSnc on cognitive tests and tasks requiring motor functioning and motor planning. RR-MSc demonstrated a specific cognitive profile associated with more significant and widespread impairments. Clinical implications are discussed.