Visual evoked potentials with hemifield pattern stimulation. Their use in the diagnosis of retrochiasmatic lesions.

We measured several parameters of cortical potentials evoked by visual stimulation to produce a profile suggestive of retrochiasmatic lesions. Characteristic abnormal responses included (1) very low amplitude or absent transient visual evoked potentials (T-VEPs) after stimulation of the affected hemifield, (2) reversal of normal pattern amplitude of the T-VEP distribution after stimulation of the affected hemifield, (3) abnormal lateral occipital ratio, (4) absent or very low amplitude steady-state VEPs after stimulation of affected hemifield, and (5) abnormal midoccipital ratio.