Three distinct sequential cellular responses characterise the reaction of the adult spinal cord and brain to injury. An acute haemorrhagic phase immediately ensues after wounding, in which haematogenous cells flood the lesion site. This is followed by a subacute period during which macrophages clear necrotic debris, glial cell reactions are mobilised, the clot becomes organised, and scarring is initiated. Finally, the scar tissue contracts during a consolidation phase . Superimposed on the above primary inflammatory/scarring responses are secondary neuronal degenerative and regenerative reactions to injury, accompanied by demyelination and remyelination. The interrelations between primary and secondary responses are not understood. It was once thought that scarring arrested axon regeneration in the central nervous system (CNS), but.
