Invited review: focal nerve injury: guidance factors during axonal regeneration.

Regeneration of axons after nerve injury is not random but is often not precise, particularly after injuries that involve nerve transection. The factors that guide regenerating axons toward appropriate terminations are complex, but developments in neurobiology are beginning to indicate the mechanism that are involved. These include neurotrophic and neurite promoting factors, chemotactic influences from peripheral tissues, and the properties of the extracellular matrix. Understanding these mechanisms may indicate means of improving functional recovery after nerve injury.