Three broad categories of focal nerve injury

Three broad categories of focal nerve injury

  1. Minimal neural insult

    - Focal AP propagation failure secondary to short period of ischemia

    - slowing of nerve conduction is possible if neural blockade is incomplete with

      sparing of the relatively slower conduction fibers.

      i.e., preferential blockade of fastest-conducting fibers

   

  2. Intermediate neural injury

    - failure or slowing of AP propagation secondary to focal demyelination without

      axonal damage

    - prolonged conduction block and reduced NCV

 

  3. Severe neural insult

    - failure of AP propagation with axonal damage, i.e., Wallerian degeneration)

 

      # 1, 2 - Temporary loss of neural conduction across a focal lesion

                while axon's structural integrity is preserved.

                Restoration of blood flow or myelin recovery, nerve conduction is

                restored

      # 3 - Axon itself is damaged

             Entire nerve (axon plus myelin sheath) undergoes disintegration distal to

             injury

             completely regenerated prior to the return of function