[The change of the spinal evoked potential caused by constant-speed subacute compression of the spinal cord]

The spinal cord of the cat was squeezed by a newly designed electromotive compressor at a constant rate of 0.5-6.0 mm/h. Meanwhile, the ascending spinal potential was measured with using epidural stimulation. The earliest change of wave pattern appeared near the compression site, i.e. an augmentation of the potential which turned to positivity with prolongation of latency at the compression ratio of 32-41%. The potential gradually reduced in amplitude at more cranial levels while it augmented at the caudal levels. The first and second components of the potential which conducted along the lateral and posterior tracts respectively, blocked completely at the compression ratio of 57-82% and 45-69% respectively. After decompression, the recovery was remarkable even after a complete block. Deformation of the spinal cord, providing a change of the volume conductor, likely caused such augmentation.