Acute changes in somatosensory evoked potentials following graded experimental spinal cord compression

Amplitude and latency of cortical somatosensory potentials evoked in cats by peripheral nerve stimulation were measured before, during, and for 5 hours after injury of spinal cord segment L-7 by a predetermined degree and duration of compression. An amplitude decrease, slight and transitory, was first observed after compression reduced the segmental cross section by 60%. After an 80% compression, amplitude reduction was initially larger and lasted longer, but recovered 2.5 hours after injury to a level that did not differ statistically from control values. After total (100%) compression, evoked responses disappeared abruptly and did not recover significantly. Latency was unaltered at all degrees of compression. Structural damage increased with the degree of compression. In this model, evoked potential changes neither reflect nor predict the magnitude of acute incomplete spinal cord injury.