Integration and disintegration in the auditory and somatosensory systems during brainstem lesions

Auditory and somatosensory evoked potentials (AEPs and SEPs) were recorded in 8 patients with malignant processes in the brainstem region and 14 healthy persons under conditions of relevant and deviant stimulation. The spatial-temporal EP characteristics were evaluated and mapped. The low-voltage AEPs to simple rhythmical stimulation were recorded in patients over the whole cortical surface. During attention activation (solving selective attention tasks) there was an increase in the amplitude of the AEPs, mainly, of their mid-latency components. Under such conditions the N200 SEP components were well expressed in both hemispheres with the maximal amplitude in the medial and anterior derivations. The spatial distribution of N350 resembled that of the N200. There was an increase in N30 amplitude in both occipital derivations and its expressed reduction in the frontal areas as compared to the situation with the simple rhythmical stimulation. In patients with the brainstem pathology the increased amplitude of these components was observed mainly in the parietal and occipital cortical areas.