Pattern of thalamic nuclei atrophy in early relapse-onset multiple sclerosis

Background: Thalamic atrophy is prominent in multiple sclerosis; however, it is unclear which thalamic nuclei are most vulnerable, especially early in disease. Introduction: To investigate which thalamic nuclei differ between patients in early stages of relapsing-remitting multiple sclerosis (RRMS) versus healthy controls and examine the relationship between thalamic nuclei volume and T2 lesion volume. Methods: We derived 15 thalamic subfields from high-resolution 3T magnetic resonance images in 182 patients with early RRMS (diagnosed ≤5.0 years, median 2.0 years). Independent t-tests assessed differences between patients and 35 controls across thalamic subfield volumes. Pearson correlations assessed the relationships between thalamic volumes and T2 lesion volumes. Results: Patients had lower anterior and posterior nuclei volume than controls, whereas medial and ventral nuclei volumes were preserved. Higher T2 lesion volumes were disproportionately related to lower posterior subfield volumes. Conclusions: We found specific thalamic subfields were more vulnerable to early disease-related changes. We discuss potential mechanisms of differential thalamic subfield atrophy in early MS, including cortical demyelination, CSF toxicity, leptomeningeal inflammation, and iron deposition.