Augmented P22-N31 SEP component in a patient with a unilateral space occupying lesion.

A patient presented with a right rolandic space occupying lesion resulting in a decrease of position sense, touch and stereognosis in the left upper limb. SEPs revealed an augmentation of the right hemisphere P22 component co-existing with relative attenuation of all other right hemisphere components. The augmented P22-N31 complex represented a 'giant' potential in relation to a control group (> 2.5 S.D.). The data provide further evidence that the P22-N31 complex has separate generators from those responsible for the N20-P27-N33 components parietally and P20-N30 components frontally. The focal nature of the lesion and symptomatology are of interest.