Changes in the Somatosensory Evoked Potential During and Immediately Following Temporary Middle Cerebral Artery Occlusion Predict Somatosensory Cortex Ischemic Lesions in Monkeys

Abstract

Somatosensory evoked potentials (SEP) were recorded during and immediately following temporary middle cerebral artery (MCA) occlusion to determine whether they can be used to predict ischemic lesions to the somatosensory cortex (SI). Twenty-one cynomolgus female monkeys were subjected to four different MCA occlusion durations (15-60 min) during hypotension (45-50 mm Hg mean arterial blood pressure). The amplitude and central conduction time (CCT) of the median nerve SEP were recorded preceding, during, and following occlusion. Two groups were established based on the development of SI ischemic lesions: animals developing SI lesions formed the SI-lesion group (n = 9), and animals without ischemic lesions or with lesions outside the SI cortex formed the SI-spared group (n = 12). Changes in the SEP during and following MCA occlusion under conditions of hypotension were similar to those reported by others. The SEP disappeared in all animals within 15 min of occlusion and reappeared 5 min following reperfusion. Several differences were observed between the SI-lesion and SI-spared groups. The SI-lesion group had a more rapid decrease in SEP amplitude during the first 5 min of occlusion and had smaller SEP amplitudes and longer CCTs during reperfusion. These results suggest that changes in SEP amplitude and latency during and immediately following temporary MCA occlusion predict development of SI ischemic lesions.