The peripheral and central nervous systems are functionally
integrated regarding the consequences of a nerve injury: a
peripheral nerve lesion always results in profound and long lasting
central modifications and reorganization. (Kaas, 1991)
Does there need to be a lesion though ? A functional lesion will force changes just like an ablative lesion. Altered gait that persists from a sprained ankle or a painful knee will force central modifications and reorganization. This is why resolution of pain and aberrant function is critical. If you rehab to 80% you leave 20% on the table and that gets rewired into the system as the new norm. Remember, the entire system is watching, learning, adapting and rewiring all the time. This is why you must have a team in place to resolve all, if possible, of your client’s deficits. If you leave 20% of a problem on the table, and add endurance and strength to the “80%resolved:20%remaining”, you reorganize the central nervous system with that as the assumed norm moving forward. From this point forward, this is the architecture that all new patterns and forms are built from.  This sets up for long term rewiring of all of the connected parts, from motor, sensory, visual, gait, proprioceptive, vestibular and the list goes on and on. If you have ever wondered how a client can have so many areas of pain and dysfunction you might want to go back into their history and ask them if there was a single injury or event that occurred after which all their new problems started to stack up. 

If you are a gait analysis junkie, remember this principle above. All of the things you see in a person’s gait are not unconnected in many cases.  Much of what you see is a compensation around their problems, not the actual problem. 

Remember this principle: the peripheral nervous system attempts to repair by regrowth, the central nervous system attempts to repair by re-routing and reorganizing.

Dr. Shawn Allen