In this paper, the shape of the Somatosensory Evoked Potential (SEP) signals is analyzed to detect a focal lesion in the spinal cord of rats. SEPs can be used to reliably assess the spinal cord integrity. However traditional time-domain analysis often needs human intervention because of common difficulty in SEP peak detection due to low signal-to-noise ratio or flattening of SEPs during injury. We have proposed a novel shape analysis technique for SEPs, in which we obtain the slope information for the entire waveform in specific time bins. This technique does not involve any peak detection, and can be used without human intervention. We studied the effectiveness of this technique in a focal Experimental Autoimmune Encephalomyelitis model, in which a focal demyelinating lesion is induced in the spinal cord by injecting cytokine-ethidium bromide into dorsal white matter at T8 after immunization using Myelin Oligodendrocyte Glycoprotein combined with incomplete Freund's adjuvant. The technique was applied to SEPs recorded before and after lesion from 12 rats. The results showed the effect of injury to the SEPs from hindlimbs, hence demonstrating great potential of this technique to detect an injury to the spinal cord.