Human nerve repair can happen in the peripheral nerves. Peripheral nerve fibres that are crushed or even cut may slowly regenerate if the cell body is undamaged. If the connective tissue in which the nerve travels is also intact this can aid in regeneration.
Regeneration does not occur in nerves in the brain or spinal cord. These fibres become wrapped in scar tissue.
When a nerve fibre is cut off from the cell body by an injury the part beyond the cut degenerates. The myelin also degenerates.
The cell body stimulates the growth of nerve sprouts from the remaining fibre, one of these may join up with its original connection.
Growing 2-4mm a day the new nerve fibre reaches its previous connection. Function and sensation are slowly restored.