Differential patterns of memory performance in relapsing, remitting and secondary progressive multiple sclerosis

Background: Memory dysfunction is common in multiple sclerosis (MS). A retrieval failure has been reported as the primary cause for the memory deficits, although some studies also described a faulty acquisition.
Aims: The aim of the study was to examine memory function in relapsing remitting (RR) and secondary progressive (SP) MS patients, analyze the patterns of performance and to investigate whether disease course influences this performance.
Design and settings: Case-control prospective study conducted in a clinical setting.
Materials and Methods: Fifty-five RR, 23 SP MS patients and 80 normal subjects were evaluated with a comprehensive neuropsychological battery. Memory was assessed with tasks from the Signoret memory battery. Attention and executive function were also assessed.
Statistical Analysis : Univariate analysis of variance, Mann-Whitney U-test, multivariate logistic regression and Chi-square test were used as appropriate.
Results: MS patients performed significantly worse than controls on almost all measures of memory ( P < 0,001). MS subgroups differed in tasks of delayed recall (logical memory- P =0,019; wordlist delayed recall, P < 0,001), semantic cued recall ( P < 0,001), recognition trials ( P =0,006) rate of forgetting ( P < 0,001) and confabulation and intrusion errors ( P =0,004).
Conclusions: Memory is consistently impaired in MS patients and disease course differentially affects the pattern of performance. SP patients show greater difficulties and a more pervasive pattern of dysfunction than RR patients. Delayed recall was the most affected memory measure and performance on this task discriminates between RR and SP MS patients. Relapsing remitting patients performed within the mildly impaired range while SP patients showed a moderate to severe impairment.