Does focal inflammation have an impact on cognition in multiple sclerosis? An MRI study

Objective: Cognitive impairment concerns a significant percentage of patients with multiple sclerosis (MS). A transient impairment of cognition with a simultaneous presence of non-symptomatic gadolinium (Gd)-enhancing lesions in patients with MS was previously described. Our study aimed to evaluate modifications in cognitive function before and after the occurrence of asymptomatic MRI gadolinium (Gd)-enhancing lesions in relapsing MS patients. Patients and methods: All patients underwent a neuropsychological evaluation before (30–60 days) and after (30–60 days) brain MRI with Gd administration. Patients were classified as Gd positive (presence of enhancing-lesions) and Gd negative (absence of enhancing-lesions). We also recruited a healthy controls group underwent to the same neuropsychological assessment for two times with the same timing of MS patients. Results: We included 84 relapsing-remitting patients and 40 healthy controls. Brain MRI results showed that 14/84 (16.7%) patients had asymptomatic Gd-enhancing-lesion. No significant variation in cognitive performance between baseline and follow-up was observed in patients with or without MRI-enhancing lesions. However, an increase between baseline and follow-up was observed in the mean scores of the Symbol Digit Modality Test (41.9 at baseline versus 46.7 at follow-up, p :< 0.001). This increase was significantly lower in Gd positive patients compared to Gd negative patients (mean increase 1.1 in Gd positive versus 4.9 in Gd negative, p: < 0.001) and to healthy controls groups (mean increase 7.2; p < 0.001) Conclusions: In our study, the absence of a practice effect in Gd positive compared to Gd negative patients and to healthy controls suggests a possible role of focal inflammation on cognitive function of MS patients.