Relationship between brain volume loss and cognitive outcomes among patients with multiple sclerosis: a systematic literature review

Patients with multiple sclerosis (MS) experience varying rates of brain volume (BV) loss ranging from 0.5 to 1.5 % per year. In addition, 66 % of patients with MS experience cognitive impairment, resulting in impact on daily activities. A systematic literature review (2003-2013) was conducted to identify all studies reporting a relationship between whole BV measures and selected patient outcomes measuring cognition, including the Symbol Digit Modalities Test (SDMT), Paced Auditory Serial Addition Test (PASAT) and MS Functional Composite (MSFC) scores. We identified 18 studies reporting associations between whole BV and cognitive outcomes. Six studies (33 %) examined the association between BV and SDMT; all six studies reported that BV loss (BVL) was significantly associated with a decline in SDMT scores (all p < 0.05). Among 14 studies (78 %) that examined the association between BV and PASAT scores, 12 (86 %) found a significant relationship between BVL and lower PASAT scores (all p < 0.05). Of the seven studies (39 %) that looked at BV and MSFC, six studies (86 %) found BVL significantly associated with lower MSFC scores (all p < 0.05). Our study demonstrated that BVL is associated with declines in cognition in MS patients across several cognition measures. The results of this study suggest that BV is a critical component of disease activity and progression in MS and has implications for treatment decisions to minimize BVL and preserve cognitive functioning.