ERPs in multiple sclerosis

Involvement of cognitive functions is detectable in about 50% of patients w ith multiple sclerosis (MS). One important element seems to be the interrup tion or temporal distortion of the cross-talk among cortical associative ar eas and between cortical and subcortical structures as a consequence of dem yelination and axonal degeneration, as occurs in the so-called subcortical dementias. There is a general agreement among recent studies that P300 late ncy is prolonged and amplitude is reduced in MS. Altered scalp topographic distribution is also frequent. Similar results were found in 54 MS patients . Both early and late components resulted prolonged as observed in subcorti cal dementia. P300 abnormalities were correlated with neuropsychological fi ndings and magnetic resonance imaging evidence of confluent periventricular lesions. Topographically. P300 was significantly decreased in amplitude ov er central-anterior regions. Considering the functional aspects of cognitiv e dysfunction, 30 definite MS patients were studied by positron emission to mography. All patients with metabolic thalamic involvement had P300 abnorma lities. Moreover, in the abnormal P300 group, significant hypometabolism wa s found in thalamic and in temporo-parieto-occipital regions. These results suggest that impairment of specific areas such as the thalamus is fundamen tal in the correct genesis of this wave.