Objective: We assessed the occurrence, extent, and frequency of formation of cortical lesions (CLs) in patients with relapsing-remitting (RR) and secondary progressive (SP) multiple sclerosis (MS), and their relationship with cortical atrophy and disability progression.
Methods: One-hundred seven MS patients (76 RRMS and 31 SPMS), enrolled in a prospective, longitudinal magnetic resonance imaging (MRI) study, were assessed clinically and by brain MRI (including a double inversion recovery sequence) 3 years after study initiation. CL number and volume, T2 white matter (WM) lesion volume, gray matter fraction, and expanded disability status scale (EDSS) were measured.
Results: At baseline, CLs were detected in 64.4% of RRMS and 74.2% of SPMS patients. During follow-up, 132 new CLs were found in 44 RRMS patients (57.9%; 0.8 new CL/patient/yr) and 61 in 15 SPMS patients (48.4%; 1.0 new CL/patient/yr). Among these patients, only 31 also showed at least 1 new WM lesion. CL number and volume increases were higher in the 52 patients with a clinical worsening compared with those without (p < 0.001). Baseline CL volume correlated with baseline EDSS (r = 0.36, p < 0.001) and EDSS changes over time (r = 0.51, p < 0.001). Baseline CL volume was an independent predictor of EDSS accumulation and GM volume change at follow-up in both patient groups. In SPMS patients, baseline T2 WM lesion volume was another independent predictor of EDSS worsening.
Interpretation: In relapse-onset MS, CLs accumulate over time and are associated with disability progression. The quantification of CLs might represent an additional useful paraclinical tool to monitor MS evolution.