Brain changes after peripheral nerve repair: limitations of neuroplasticity.

Neuroplasticity is the capacity of the central nervous system to adapt to external or internal stimuli. It is being increasingly recognized as an important factor which contributes to the successful outcome of nerve transfers. Other much more well-known factors are the number of axons that cross the coaptation site, the interval between trauma and repair, and age. Neuroplasticity is mediated by synaptic and neurotransmitter changes which underlie activation of previously existing but low-active connections in the brain. Dendritic sprouting and axonal elongation might also take place but is likely less prominent. We review different factors that play a role in neuroplasticity and functional regeneration after specific nerve transfers. These factors include, amongst others, the distance between cortical areas of the donor and receptor neurons; the presence versus absence of pre-existing low-active inter-neuronal connections; gross versus fine movement restoration; rehabilitation; brain trauma and very important: the age. The potential for plastic adaptation should be taken into consideration if the surgical strategy and postoperative rehabilitation are planned, as its influence on results cannot be denied.