Background Multiple sclerosis (MS) is a chronic demyelinating disease in which cortical lesions (CLs) are important contributors to disability but remain less extensively characterized than white matter lesions. Quantitative MRI markers, such as lesion-associated T1 intensity, provide insight into tissue integrity, yet longitudinal dynamics of CLs have not been systematically studied. Methods We conducted a longitudinal 7T MRI study of 16 patients with MS. CLs were manually segmented and categorized as baseline, new, expanding, or remyelinating. Lesion-associated T1 intensity was quantified, and linear mixed-effects models were applied to assess longitudinal change across repeated measures. Results No significant changes in T1 intensity were observed across 3, 6, 9, and 12 months, indicating stability over the analyzed time series (p-value > 0.1). Across observation periods of up to 5 years, both new cortical lesion formation (11 patients) and expanding cortical lesions (16 patients) were identified, consistent with progressive cortical pathology. Conclusion This study was the first longitudinal analysis of cortical lesion evolution with frequent early scan time-points using ultra-high-field 7T MRI in patients with MS. The findings underscore the utility of 7T MRI for tracking cortical pathology. Future work should incorporate clinical outcomes to construct a comprehensive model linking imaging changes with patient function.