Abnormal excitability in injured axons

This chapter discusses the abnormal excitability of injured axons. Injured axons display abnormal hyperexcitability. This is expressed in the form of abnormal sensitivity to a broad range of depolarizing stimuli: physical, chemical, and metabolic. Associated with this hyperexcitability are a number of processes that tend to amplify the abnormal afferent barrage. Prominent among these are different forms of axon-to-axon cross-excitation. The underlying hyperexcitability as well as the specific stimulus sensitivities are the result of remodeling of membrane electrical properties in end-bulbs, sprouts, and patches of demyelination. Of particular importance to this remodeling process is accumulation of Na⁺ channels in the local axonal membrane.