Why can spinal cord injury cause permanent loss of movement and sensation below the injury?

The permanent loss of movement and sensation following a spinal cord injury occurs because the central nervous system lacks the ability to effectively repair itself after destructive trauma.12

When the spinal cord is injured, the neurons that are destroyed are not replaced by the body. While severed axons may attempt to sprout new growth from the cut ends, they are unable to form functional connections within the spinal cord. Because the spinal cord acts as the primary pathway for signals traveling between the brain and the rest of the body, this inability to reestablish effective neural pathways results in a permanent loss of voluntary movement and sensation for the areas of the body located below the level of the injury.21

In contrast to the central nervous system, axons in the peripheral nervous system are capable of regeneration, which allows for the potential reestablishment of connections with muscles or sensory organs following injury.2