Motor and Sensory Evoked Potential in the Evaluation of Increased Intracranial Pressure in Cats

ABSTRACT

Motor evoked potential(MEP) and sensory evoked potential(SEP) were recorded in 30 experimental cats in accordance with change of intracranial pressure. MEP was obtained on the thoracic cord after electric stimulation through a ball electrode directly installed on the cerebral motor cortex. SEP was elicited on the cerebral cortex after stimulation of thoracic cord. Experimental animals were composed of control group(10 cats) and raised intracranial pressure (ICP) group(20 cats) which included a group of 10 cats with 30 mmHg increased ICP and another group of 10 cats with 50 mmHg elevated ICP. Each evoked potential according to changes in ICP was obtained and the results were as follows 1) MEP in control group showed that latency was 14.8+/-0.8 msec and amplitude was 24.4+/-2.1 microV. MEP after elevation of ICP showed more profound change in 50 mmHg increased ICP group than in 30 mmHg increased ICP group. Latency was prolonged by 152%(37.4+/-1.8 msec) of control group and amplitude was reduced to 82%(4.58+/-1.2 microV) of control group in the 50 mmHg increased ICP group. Recovery of MEP changes from increased ICP by reduction of the pressure was more prominent in 30 mmHg elevated group than 50 mmHg elevated group. 2) In control group SEP showed that latency was 25.38+/-1.5 msec and amplitude was 22.8+/-1.4 microV. SEP after elevation of ICP showed more profound change in 50 mmHg increased ICP group than 30 mmHg increased ICP group. Latency of SEP in 50 mmHg increased ICP group was prolonged by 54%(39.18+/-2.2 msec) of control group and amplitude reduced by 47%(10.98+/-0.9 microV) of control group was more prominent in 30 mmHg elevated group than 50 mmHg elevated group. changes in MEP after raised ICP were more remarkable than that of SEP. The degree of Recovery from raised ICP was more prominent in 30 mmHg group than 50 mmHg group. This study indicates that because change of MEP is more sensitive than that of SEP in the evaluation of cerebral function in case of increased ICP, MEP might be a paramount indicator in the evaluation of cerebral injury. Recording of MEP as well as ICP monitoring system might be a new method for the early detection of changes in cerebral function.