Mismatch negativity (MMN) in multiple sclerosis: an event-related potentials study in 46 patients

Objective:To assess pre-attentive detection mechanisms indexed by MMN component of auditory Event-Related Potentials (ERPs) in Multiple Sclerosis (MS) patients.

Methods:46 MS patients (mean age 43.7 years, mean disease duration 10.1 years, mean EDSS 4.6) and 46 matched controls were assessed with ERPs elicited by a passive oddball paradigm using duration deviants. Auditory P50, N1, P2 components were recorded. MMN and P3a components were calculated as the difference potential between deviants and standard stimuli. Eighteen of these 46 patients underwent also global psychometrical assessment and were sorted in cognitively normal and impaired patients. ERPs of these two groups of patients were compared.

Results:MS patients showed reduced MMN and P3a areas as compared to controls, besides exogenous N1-P2 complex amplitude reduction. Among the 18 patients investigated with neuropsychological testings, six were cognitively impaired and 12 cognitively unimpaired. Patients with a global cognitive impairment had reduced MMN as compared to cognitively unimpaired patients.

Conclusions:Auditory MMN and P3a components of auditory ERPs are altered in MS patients. MMN alterations are more pronounced in cognitively impaired patients.

Significance:MMN and P3a areas reduction suggests that MS patients are prone to pre-attentive auditory information processing deficits, besides previously described controlled information processing difficulties. Moreover, MMN alterations may represent an objective index of cognitive disturbances in MS patients.