|Cognitive dysfunction can be found in up to 65% of multiple sclerosis (MS) patients even though only small percentage of MS patients present with severe dementia. Most frequent cognitive deficits are present in recent memory, information processing speed, executive function, and visuospatial perception although no abnormalities are detected in general intelligence, language, short term, and implicit memory. Little information is present concerning the natural history of cognitive dysfunctions during the course of the disease. Clinical studies on this field have revealed that some MS patients show neurobehavioral changes, even in the early phases of the disease, whereas others never develop such changes or complain about it. Large percentage of MS patients who show intact mental capacity on neurological examination are however shown to be actually impaired Considerable interest exists in the utilization objective and easily administered measures of cognitive dysfunction that can be used to follow patients and also to demonstrate the clinical benefits of various therapeutic interventions. Event related potential (ERP) records electrical manifestations of the brainâs perception and response to external stimuli.