[Working memory in multiple sclerosis: a review].

Introduction: Impairment of working memory (WM) is frequently reported in multiple sclerosis (MS) patients. However, the various methodologies used, as well as the populations selected for study, hinder the interpretation of results. The aim of this study is to propose a review about WM in MS.

Method: Twenty studies have presented results on WM with neuropsychological assessment.

Results: All studies conclude that WM is impaired in MS. Reduced processing speed would be central, with major impact on WM performance. According to Baddeley's model, difficulties may be located at the level of the central executive. MS patients would be sensitive to tasks with a high cognitive load. However, performances seem to become better when the processing speed is adapted. Explanatory models relating to this kind of impairment have been proposed from imaging studies. Compensation could mask deficits in WM at the early stage of the disease, but would become blurred with advancing illness and increasing load required for the task. CONCLUSIONS/PROSPECTS: In order to assess WM, adapted tools should be proposed to MS patients. Focus should be placed on processing speed. Further studies are needed, for instance to examine the dissociation of the processes operating within the central executive as described in Miyake's model. Imaging investigations have provided essential data helpful for understanding compensation mechanisms. These data should be useful for developing adapted remediation plans to compensate for the crippling impairment observed in everyday life.