[Frontal SEPs and parietal SEPs following median nerve stimulation--clinical correlation and consideration of their generation sites].

In order to know the characteristics of frontal and parietal SEP components following median nerve stimulation, 25 patients with unilateral cerebral lesions above the thalamus were examined, and their SSEPs were carefully compared with the clinical and radiological findings. In 10 normal subjects, there were three cortical components of the frontal SEPs (P 20-N 28-P 44) and four those components of the parietal SEPs (N 18-P 22-N 26-P 42). In patient's group, central conduction times (CCTs) between components P 13 and each cortical component were measured and the latency differences between normal side and affected side were calculated. When the latency differences increased over 3 S.D. from the mean of the control values or the some cortical components disappeared, they were regarded as abnormal. According to the combination of the abnormalities in frontal and parietal SEPs, three groups were classified as follows: group 1; frontal and parietal SEPs were normal (n = 10), group 2; frontal and parietal SEPs were both affected (n = 10), group 3; parietal SEPs were affected but frontal components were preserved in normal range (n = 5). CT scan showed that the region from internal capsule to cortex around the central sulcus remained intact in the patients of group 1, while this region was involved in various degrees in all cases of the group 2. In patients of group 3, frontal or parietal regions were variously affected. Both the motor and sensory functions were mainly intact in group 1, and disturbed in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)