Nerve Trauma

Normal -- Normal nerve transmission may be disturbed from high pressure exerted for a short time, from moderate or low pressure exerted for intermittent or long periods. The subtlety of pressure that can cause entrapment neuropathy is illustrated by fluid accumulation causing entrapment at the carpal1 or tarsal2 tunnel, in pregnancy, premenstrual syndrome, or the ileocecal valve syndrome. The irritation creating symptoms is often long-standing; it causes an inflammatory response in the nerve and maintains its improper function. Short-term, subtle irritation on a nerve does not appear capable of changing the characteristics of its function on a constant or permanent basis. It is necessary to diagnose the entrapment early so that conservative treatment will be effective. Chronicity increases the chance that surgical decompression may be necessary.

Neurapraxia is the lesser of the types of nerve involvement. It is a segmental block of axonal conduction due to a focal region of demyelinization of the nerve. The nerve has continuity, but conduction cannot be carried out over the demyelinated area. With only slight myelin damage there may be conduction, but it is slowed, requiring greater time to activate the widened nodal region. This is probably the type of nerve involvement present in the more subtle types of entrapment often observed in routine applied kinesiology examination, when the patient is not aware of symptoms.

Axonotmesis is the loss of continuity of nerve axons, but with continuity of the connective tissue sheath. This leads to wallerian degeneration of the distal part of the nerve. Following wallerian degeneration, the proximal part of the nerve attempts to regrow. “This growth occurs at the rate of approximately 1 mm per day, 1 cm per week, or 1 inch per month.” Obvious symptoms and signs of peripheral nerve entrapment are present in this condition. When the entrapment is released, repair begins and the patient can expect to return to normal or nearly normal. The main factor is time for regrowth and maintenance of an entrapment-free condition.3

Neurotomesis is the separation of the axon and is the most advanced involvement. The separation of the nerve from its nutritive sources causes wallerian degeneration, the fatty degeneration of the nerve fiber. Regeneration may still take place and will result in regaining continuity or in forming a neuroma illustrated below.

Neurotomesis regaining continuity. Because of the loss of continuity of the nerve's supporting elements there is only a chance that the nerve will connect with the proximal portion. If it does the slow process of regeneration can take place. The amount of regeneration to normal is variable.

Neurotomesis failing to regain continuity is illustrated. The continued nerve regeneration causes a neuroma to develop.