Denervation

Denervation is any loss of nerve supply regardless of the cause. If the nerves lost to denervation are part of the neuronal communication to a specific function in the body then altered or a loss of physiological functioning can occur. Denervation can be caused by injury or be a symptom of a disorder like ALS and post-polio syndrome. Additionally, it can be a useful surgical technique to alleviate major negative symptoms, such as in renal denervation. Denervation can have many harmful side effects such as increased risk of infection and tissue dysfunction.

The loss of nerve supply can be caused by injury, disorders, or result from a surgical procedure.

Denervation may be the result of nerve injury. The three main types of nerve injury are neurapraxia, axonotmesis and neurotmesis. These three types distinguish between the severity of the nerve damage and the potential for recovery after the damage. After an injury in which some nerves are damaged, the brain has shown capabilities in rewiring or rearranging neuronal circuitry. This plasticity allows for the brain to compensate for the loss in neuronal communication resulting from injury.

Denervation processes have a strong association with the symptoms seen in post-polio syndrome. Those with post polio syndrome are undergoing a constant process of denervation and reinnervation. This process occurs after acute poliomyelitis and leads to increased motor unit areas over time. The motor unit areas soon increase to a point where reinnervation is no longer possible causing an uncompensated denervation of motor units which leads to muscle atrophy and loss of muscular strength. Following an acute polio infection diagnosis symptoms such as fatiguability, general weakness and pain are believed to be correlated to muscle denervation.

Much like post-polio syndrome, amyotrophic lateral sclerosis also has similar symptoms of motor neuron degeneration leading to general weakness and in some cases paralysis. The type of symptoms experienced can depend on which particular areas of the body experience the loss in nerve supply. This process of denervation is however different from post-polio syndrome in that it only involves upper and lower motor neuron degeneration and does not experience a process of constant reinnervaiton and denervation.

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