Somatosensory evoked potentials as a measure of experimental XXXX .

@entity64 @entity2806 @entity2500 @entity1188 @entity468
Somatosensory evoked potentials (SEP's) reflect the integrity of the central neuronal pathway, and as such may be used to assess function that remains during a variety of cerebral insults. To evaluate the natural history and utility of SEP's during experimental @entity2806 and @entity1188 , SEP's were measured in 17 adult @entity468 at 24 hours and 1 hour prior to right @entity2500 , and again immediately afterward and at either 6 hours (five @entity468 ) or 24 hours (six @entity468 ) post-occlusion. Before occlusion of the right MCA, the SEP's were identical in the right and left hemispheres. After occlusion, there was a significant slowing of the interpeak latency of the first positive peak (P1) in the right hemisphere (3.53 +/- 0.6 msec before compared to 3.99 +/- 0.6 msec after occlusion, p less than 0.001). Maximal slowing in right hemisphere P1 latency was seen in those animals in which the @entity64 extended into the thalamus (4.38 +/- 0.1 msec). This was significantly slower than left hemisphere values (3.92 +/- 0.32 msec, p less than 0.01). The ipsilateral cortical components of the SEP's, the second positive peak (P2), and the major negative deflection (MN) were slowed in all @entity468 immediately after right MCA occlusion compared to preocclusion measurements (p less than 0.001). Severe @entity1188 in the mid-suprasylvian and posterior ectosylvian gyri (including the somatosensory cortex) resulted in a greater slowing of the latency of MN compared to less severe @entity1188 in that region (20.6 +/- 3.9 msec versus 16.4 +/- 1.1 msec, p less than 0.05). There was a precipitous decrease in the amplitude or voltage of the ipsilateral P2-MN complex immediately after occlusion (5.32 +/- 0.4 microV before compared to 0.98 +/- 0.3 microV after occlusion, p less than 0.001). Therefore, the central latencies and cortical amplitudes of the SEP's are sensitive experimental tools as indicators of the onset and extent of a cerebral ischemic insult.
