Impaired cognitive function may represent damage to brain regions that are not involved in physical functions, hence may not be detected during routine neurological assessment. Despite the high prevalence of cognitive impairment in MS, cognitive function is not assessed routinely in clinical practice. The perception that cognitive assessments are costly, time-consuming, complicated, and difficult to administer and interpret has contributed, at least in part, to the failure to incorporate cognitive testing into standard clinical evaluation of patients with MS.
Cognitive impairment may also reduce the ability of patients to comprehend and adhere to treatment concepts (Bobholz 2003). Early detection of cognitive impairment is important to initiate therapeutic intervention, even though the optimal treatment of cognitive decline in MS is at the moment controversial.
Preliminary studies suggest an essential role of disease modifying therapies (DMT) in inhibition of cognitive deterioration in patients with MS (Barak 2002, Flechter 2007). Data about long term cognitive performance of multiple sclerosis patients treated with natalizumab is limited. One study demonstrated in MS patients treated with natalizumab an improvement in SDMT (Symbol Digit Modalities Test) of 16.4% over a period of 2 years (Piehl 2010). SDMT is a screening tool for cognitive impairment in MS patients, mainly measuring working memory and speed processing. As SDMT only covers a part of the neurocognitive impairments seen in MS patients, there is a need for further studies to gain a more complete picture.
