Olfactory Evoked Potentials and Brain MRI Outcomes in Multiple Sclerosis Patients: A Cross-Sectional Study.

Olfactory dysfunction (OD) is an underestimated symptom in multiple sclerosis (MS). Multiple factors may play a role in the OD reported by MS patients, such as ongoing inflammation in the central nervous system (CNS), damage to the olfactory bulbs due to demyelination, and the presence of plaques in brain areas associated with the olfactory system. Indeed, neuroimaging studies in MS have shown a clear association of the OD with the number and activity of MS-related plaques in frontal and temporal brain regions. However, these studies have used only psychophysical tests to evaluate the OD in MS patients. Olfactory Event-Related Potentials (OERPs) are a method to assess olfaction with the clear advantage of its objectivity in comparison with psychophysical tests. The aim of this study was to investigate the association between the parameters of OERP components (latency and amplitude) and the lesion load of the brain regions which are involved in olfaction in a cohort of relapsing-remitting (RR) MS patients. In this cross-sectional study, we enrolled 30 RRMS patients and 30 healthy controls. The parameters of OERP components and magnetic resonance imaging data (lesions in the CNS) were analyzed in RRMS patients. The association found between the RRMS patient groups with and without OERPs and the number of lesions in the frontal area as well as the correlation between the lesion load in the temporal area and OERP parameters suggest how brain alterations may impact on olfactory performance in MS. In addition, the predictive value of the number of lesions in the frontal and parietal areas for P2 amplitude also highlights the potential for OERP measures to serve as markers for disease progression in MS. This approach to assess the olfaction in MS could improve our understanding of the disease's neurological impact and contribute to the development of new targeted interventions to mitigate olfactory sensory deficits.