Differences in cognitive profile between remitting and progressive Multiple Sclerosis phenotypes: the visuospatial domain as a key component

AIMS: Multiple sclerosis (MS) is a neurologic disease characterized by the occurrence of wideapread demyelinating lesions in the central nervous system (CNS). Cognitive impairment is frequently associated with MS, at both the earlier and later stages of the disease (Mendozzi et al., 1993). Rao Brief Repeatable Battery (BRB-N) of Neuropsychological Tests is a widely accepted and used screening battery to assess cognitive functioning in MS (Rao et al., 1991; Amato et al., 2006). The present study aims to identify possible cognitive profiles characterising patients with relapsing (RMS) and progressive (PMS). MATERIALS: 155 patients (RMS: n=57, 43 females and 14 males; PMS: n=98, 48 females and 50 males) were enrolled. All participants underwent a comprehensive neuropsychological examination with BRB-N. METHODS: After z-transformation of the scores, group comparisons in subtests of the BRB-N were evaluated with the Mann–Whitney U test. A Principal Component Analysis (PCA) was then performed to identify factors explaining the overall performance on MS groups. A binary logistic regression was computed inserting age, sex, years of education, EDSS and regression factors scores as predictors of patients’ current disease phenotype. RESULTS: RMS and PMS were significantly different in some neuropsychological subtests included in the BRB-N, in particular for oral Symbol Digit Modalities Test (SDMT) (Mann–Whitney U test=2147.50, p=.017), delayed recall of Selective Reminding Test (SRTD) (Mann–Whitney U test=2225.00, p=.034) and Word List Generation (WLG) (Mann–Whitney U test=2225.00, p=.035). The PCA (Bartlett’s χ2=771.37, p<.001) showed a first component accounting for verbal memory and lexical-semantic abilities; a second component accounting for attentional abilities and a third component for spatial abilities. The subsequent binary logistic regression (Cox and Snell’s R2=.570, Nagelkerke’s R2=.779) showed that EDSS, age, sex and only the spatial factor were significant predictors of current disease phenotype. DISCUSSION: SDMT, SRTD and WLG are useful tools to differentiate the two phenotypes. Between cognitive domains, only the spatial one seems to be crucial to discriminate the current phenotype. We hypothesized that deficit in visuospatial organization and of mental spatial representations may originate from a “parietal” dysfunction due to gray matter damage. CONCLUSION: Our findings suggest that spatial domain is the main factor that allows differentiating the cognitive profile of RMS and PMS phenotypes. References Amato, M. P., Portaccio, E., Goretti, B., Zipoli, V., Ricchiuti, L., De Caro, M. F., ... & Trojano, M. The Rao’s Brief Repeatable Battery and Stroop Test: normative values with age, education and gender corrections in an Italian population. Multiple Sclerosis Journal, (2006), 12(6), 787-793. Mendozzi, L., Pugnetti, L., Saccani, M., & Motta, A. Frontal lobe dysfunction in multiple sclerosis as assessed by means of Lurian tasks: effect of age at onset. Journal of the neurological sciences, (1993), 115, S42-S50. Rao, S. M., Leo, G. J., Bernardin, L., & Unverzagt, F. Cognitive dysfunction in multiple sclerosis. I. Frequency, patterns, and prediction. Neurology, (1991), 41(5), 685-691