Evoked potential and behavioral outcomes for experimental autoimmune encephalomyelitis in Lewis rats

A reliable outcome measurement is needed to assess the effects of experimental lesions in the rat spinal cord as well as to assess the benefits of therapies designed to modulate them. The Basso, Beattie, and Bresnahan (BBB) behavioral scores can be indicative of the functionality in motor pathways. However, since lesions are often induced in the more accessible dorsal parts associated with the sensory pathways, the BBB scores may not be ideal measure of the disability. We propose somatosensory evoked potential (SEP) as a complementary measure to assess the integrity of sensory pathways. We used the focal experimental autoimmune encephalomyelitis (EAE) model, in which focal demyelinating lesions were induced by injecting cytokine-ethidium bromide into dorsal white matter after MOG-IFA immunization. Both the SEP and BBB measures reflected injury; however, the SEP was uniformly and consistently altered after the injury whereas the BBB varied widely. The results suggest that the SEP measures are more sensitive and reliable markers of focal spinal cord demyelination compared to the behavioral measures like the BBB score.