Early multimodal predictors of conversion from clinically isolated syndrome to multiple sclerosis: integrating MRI lesion burden with tibial somatosensory evoked potentials

Introduction : Clinically isolated syndrome (CIS) represents the earliest clinical expression of central nervous system demyelination. Early stratification of conversion risk is clinically important, as it can guide the timing of disease-modifying therapy in patients who are likely to develop multiple sclerosis (MS). Aim : To determine whether the combined assessment of MRI T2-lesion burden and tibial somatosensory evoked potentials (SSEPs) improves prediction of MS conversion over 5 years. Materials and methods : In a prospective five-year follow-up, 50 CIS patients and 40 healthy controls underwent baseline MRI, clinical assessment, and multimodal evoked potentials (VEP, SSEPs). Conversion to MS was determined according to the 2017 McDonald criteria. Results : Forty-two CIS patients (84%) converted to MS. A high MRI T2 lesion burden (>9 lesions) and delayed tibial SSEP P37 latency were strong and independent predictors of conversion (OR 4.8, 95% CI 2.3–9.6, p <0.001; OR 3.5, 95% CI 1.9–6.7, p =0.002). The combined MRI+SSEP model showed better overall predictive performance compared with either modality alone, reaching 87% accuracy. Kaplan–Meier survival analysis confirmed shorter conversion-free intervals in patients with abnormal SSEPs ( p <0.01), consistent with early functional involvement of long sensory pathways. Conclusion : MRI lesion burden and tibial SSEP P37 latency offer complementary markers predicting an increased risk of earlier conversion from clinically isolated syndrome to multiple sclerosis. Including SSEPs in the baseline evaluation of CIS may improve prognostic precision and support more evidence-based therapeutic decisions.