Large check size pattern reversal visual evoked potentials - Full and sectorial field stimulation in multiple sclerosis and controls.

Pattern reversal visual evoked potentials have been used to study optic neuritis. Although smaller check size in the central fields are more sensitive, larger check sizes can be advantageous for patient fixation and in poor vision. We compared sectorial central and peripheral hemisurround stimulus with commonly used full- and half- field stimulus using large check sizes (65') in the context of optic neuritis and multiple sclerosis. Of 19 female and 16 male control subjects studied, females had shorter P100 latencies and larger amplitudes than males. In 9 of the 18 patients with VEP abnormalities, the central field abnormalities were greater than those recorded with the full field response. The results confirm for the first time that central field stimulation using large checks can show a greater extent of abnormality than can be appreciated with large check full field stimulation alone, and could be commonly employed to improve yield in the investigation of optic neuritis. The data suggest that it is necessary to collect separate gender-specific laboratory normal values using this check size.