The Changes of Somatosensory Evoked Potentials in Experimental Cerebral Missile Injury and the Effect of Mannitol

Kim, Moon Chan; Huh, Choon Wong; Ha, Young Soo; Kang, Joon Ki; Song, Jin Un

Abstract

Since every component of the evoked response is considered to relate with topographically specific neural structure, it is possible that the location and severity of brain dysfunction could be defined by careful analysis of evoked responses. The purpose of this investigation was to study the change in cardiopulmonary functions, somatosensory evoked potential(SEP) following a right occipitofrontal missile injury in cats and to evaluate the effects of mannitol on them. Forty adult cats weighing 2.7 to 4.2 Kg were divided into operated control(n=20) group and mannitol treated group(n=20). In each group cardiopulmonary functions and SEP were checked on 1 min, 10 min, 30 min, 1 hour and 6 hours after missile injury. 1) After injury with a pellet at 90m/sec, there was rapid rise in intracranial pressure, bradycardia, changes in blood pressure and marked alteration in respiration. 2) The somatosensory evoked potential was detected shortly after injury and markedly altered in shape. The early components(N0, N1) of the SEP were suppressed first, followed by the late component(N2) of the SEP in the control group. This suggests that the specific somatosensory pathways are most vulnerable to high kinetic missile-injury. The late component of SEP(N2) was easily and severely suppressed possibly used due to functionally interrupted brainstem multisynaptic pathway and nearly not recovered. At an intracranial pressure(ICP) of 29 cmH2O, the early components(N0, N1) of SEP were significantly suppressed to 80% of the normal control. At the ICP higher than 40 cmH2O, not only N0, N1 appeared flat, but also the N2 was suppressedzz.