Evoked potentials in the diagnosis of multiple sclerosis.

The diagnostic value of the EP tests among patients suspected of having multiple sclerosis depends on the number of silent lesions the tests reveal. This number is influenced by technique, normal material, evaluation criteria, diagnostic classification and definition of silent lesions. Although the total number of EP abnormalities is higher among patients with definite MS, the incidence of subclinical lesions found by the tests is greater in patients with an uncertain diagnosis. In such patients, VEP revealed a silent lesion in 50%, BAEP in 38%, but SEP in only 13%. An abnormal EP recording has the same diagnostic value as has an abnormal sign, so there is no need to perform an EP test if the clinical examination shows involvement of the pathways. Normal recordings may also be valuable in reassuring patients with uncharacteristic symptoms that they are probably not suffering from MS.