Analysis of gastrocnemius compound muscle action potential in rat after death: significance for the estimation of early postmortem interval

The estimation of postmortem interval is of great importance in forensic me dicine. Changes in the properties of excitable tissue provide another possi ble means by which the time of death can be estimated. This paper reports t he monitorization of the compound action potentials recorded from gastrocne mius muscle by means of sciatic nerve stimulation in rats before and after death. The sciatic nerve was stimulated using rectangular impulses of 0.1 m s duration and intensities ranged between 1 and 100 mA while the rat was al ive. Subsequently, the rat was killed by cervical dislocation. The similar measurement procedure was performed at the moment of death and every 5 min after sequentially. There was a progressive decline in amplitude values tha t began 10 min after death. The decrease in the amplitude of the compound m uscle action potentials (CMAP) was most prominent especially when elicited with lower stimulus intensities. The mean area of the CMAPs also began to d ecrease beginning from 15 min after death. Fifteen minutes after death, the motor latencies began to prolong. Thirty-five minutes after death, the dec line in amplitude and area of mean CMAP was most prominent as the mean moto r latency. At the 40th minute, most of the CMAPs were unelicitable. During the early postmortem interval, these amplitude, area and motor latency alte rations decrease in the amplitude and area, prolongation of motor latency s eems to be well correlated with each other and this was statistically signi ficant. These findings are discussed as possible basis of a forensic method for postmortem interval estimation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.