The Evoked Potential: An Experimental Method for Biomechanical Analysis of Brain and Spinal Injury

Axial forces were applied between the shoulders and the skull of eight male Macaca mulatta monkeys. Forces from 556 to 1444 Newtons produced marked changes in blood pressure, heart rate and distraction of the cervical spinal column with minimal ligamentous disruption. Somatosensory evoked potentials recorded at the cortical and thalamic levels following dorsal column or peripheral nerve stimulation were altered prior to or during changes in heart rate or blood pressure. Similar findings were observed in the efferent responses recorded from electrodes placed on the thoracic spinal cord following stimulation of sensorimotor cortex. Studies in four monkey cadaveric isolated cervical column preparations indicate that disruption occurs with axial loads which are approximately one-third of the maximum used in the in vivo studies.