Why is the human nervous system so amazing? Humans start life with about 20 billion neurons. It is estimated that during our lifetime we use no more than 3-5% of this total. The remainder of these cells appear to provide redundancy and backup for recovery purposes. No computer has ever been designed with such a capability. This means that our nervous systems can sustain remarkable levels of insult and injury and still appear to function normally.
In 1964 Patricia Neal received an Oscar as best actress in the film “Hud.” On February 17, 1965 she experienced severe brain injury from a ruptured brain aneurysm and was completely paralyzed on her right side and unable to speak because of this. In a remarkable example of rehabilitation remaining intact brain neurons were trained to assume these functions and in 1968 Ms. Neal returned to the screen as star of the film “The Subject Was Roses”.
The remarkable ability of our nervous system and its ability to recover from insult and injury are, fortunately, legend. Fascinating examples of this are the “Giraffe Neck Phenomenon” and the disease Adhesive Arachnoiditis.
Other examples of the importance of having an “active reserve” of nervous system function are:
The “Punch Drunk” Prizefighter Syndrome
Every time someone is punched in the head there is a irreversible loss of thousands to millions of brain cells and this is cumulative. If the process is long enough, and severe enough, all reserve and redundancy is lost. Further loss then acts upon those brain cells necessary to maintain normal function. The abnormal behavior produced then becomes evident to those in the environment.
Individuals with severe brain insult show more abnormalities at the end of the day than the beginning of the day. This is due to the phenomenon of being tired. Neurologic abnormalities apparent at night may have transiently disappeared in the morning.
Individuals afflicted with poliomyelitis early in life loose significant numbers of neurons due to the disease. Because of the remarkable redundancy and backup of the nervous system they may effect, for all observable monitoring, “normal” function. It is only in the later decades of life when the neuronal population, which progressively deteriorates due to aging, reaches critical levels to maintain function that the early life loss of redundancy and backup becomes evident (usually as progressive weakness ofthe lower extremities).
In actuality most of the organ systems of the human body have great reserve and redundancy. It is possible to live a seemingly “normal” life with only one kidney, one lung, part of a liver, etc. This then brings up an important philosophic question. If, for example body tissue reserve and redundancy in an essential area is lost because of a harmful act experienced by the patient does true injury result if function, viewed externally appears to be “normal”? The example of adhesive arachnoiditis shows that it is.
The majority of patients with adhesive arachnoiditis have, because of the astonishing ability of their bodies, to recover from insult, are able to maintain a tenuous normal function. This can be, however, a fragile situation open to future change. The process of adhesive arachnoiditis is secondary to an inflammatory reaction. Nerve tissue, usually the nerve roots of the cauda equina, become enmeshed in scar tissue thus depriving them from normal nutrition ordinarily derived from cerebrospinal fluid and surrounding blood supply. The reason why agonizing and constant pain pain is not usually seen with adhesive arachnoiditis relates to the ability of this body system to adapt to the insult and appear normal. The fact that this represents only an illusion is demonstrated by the result of additional insult which can easily destabilize a previously stable environment and create constant pain and suffering for the individual as the function of the nerve cells is further impaired. This additional influence can cross the threshold of possible recovery and produce decompensation where the nerve cells exhibit their agony by sending volumes of nociceptive messages to the brain (experienced as pain and suffering).