title: Latency and amplitude abnormalities of the scalp far-field P14 to median nerve stimulation in multiple sclerosis. A SEP study of 122 patients recorded with a non-cephalic reference montage.
abstract: The frequency and characteristics of P14 abnormalities were investigated in 122 patients with probable (68), or definite (54) multiple sclerosis by recording SEPs to median nerve stimulation with a non-cephalic reference montage. The most frequent SEP abnormality found in our series (62% of abnormal results) combined latency increase and amplitude reduction of P14. Interindividual variability, inherent in absolute amplitude measurements, was by-passed by calculating the ratio between the amplitudes of far-field P9 and P14 components, which proved to be normally distributed in controls. In spite of the strong association (P much less than 0.001) between the P9-P14 interpeak interval (IPL) and the P9/P14 amplitude ratio in MS patients, the latter parameter was found to be the only abnormality in 12 patients whose P9-P14 and P14-N20 IPLs were normal. Also IPLs were increased in 12 patients with normal P14 amplitudes. These results suggest that adding the P9/P14 amplitude criterion to standard IPL data might be useful to detect conduction troubles in MS patients.
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology; D004558:Electric Stimulation; D004569:Electroencephalography / Q000379:methods; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000503:physiopathology*