Cognitive impairment in patients suffering from relapsing-remitting multiple sclerosis with EDSS < or = 3.5

Previous papers have mainly demonstrated the presence and the frequency of cognitive impairment in patients suffering from relapsing-remitting multiple sclerosis. The purpose of this study was to investigate subjects with the relapsing-remitting form of the disease and mild clinical disability (EDSS < or = 3.5), so as to quantify this deficit when the illness does not yet interfere with daily living and the ability to work.

Fifty patients and 50 healthy controls were submitted to a wide neuropsychological battery, including Wechsler Memory Scale I- (WMS), Benton Visual Retention Test D- (BVRT), Raven Coloured Progressive Matrices (RCPM), Kohs' test (KT), Judgement of Lines Orientation H- (JLO), Facial Recognition (FR) and Aachner Aphasie Test (AAT). They also underwent Clinical Depression Scale (CDQ) and State-Trait Anxiety Inventory (STAI).

The results show the presence of significant memory impairment on both WMS (P = 0.000) and BVRT (P = 0.000) in patients compared with controls. Patients were also impaired in abstract reasoning and problem-solving deficit (KT P = 0.003; RCPM P = 0.000) and in FR (P = 0.019). Cognitive decline correlated with illness duration (r = 0.761), but was independent of EDSS (r = 0.085).

Cognitive decline was present even when physical disability was not yet severe, but it was mild and did not limit patients' ability to work. The cognitive impairment outlined was of the subcortical type and correlated with illness duration. This study emphasizes the importance of cognitive examination in clinical practice. It is suggested that a complete neurological examination include tests on memory and abstract reasoning.