Short- and long-latency tibial somatosensory evoked potentials in cerebral lesions affecting Rolandic leg areas.

Short- and long-latency tibial somatosensory evoked potentials (SEPs) were studied in nine patients with clinical presentation primarily involving one lower extremity. In group 1, with extensive infarcts in the territory of anterior cerebral artery, tibial cortical SEPs were uniformly absent. In group 2, with small infarcts involving Rolandic leg areas, tibial SEPs showed a decrease in overall response amplitude and attenuation of P40. In group 3, with discrete mass lesions compressing Rolandic leg areas, P40 was preserved but might be delayed. Late SEP components (N75, P100 and N135) tended to be preserved in the patients of group 2 and 3. The data suggest that Rolandic leg areas and the neighboring cortex are crucial for short- and long-latency tibial cortical SEPs and that small lesions affecting Rolandic leg areas tend to affect short- and mid-latency SEP components.