Nerve injuries occur from all different types of medical problems. The issue can range anywhere from a gunshot injury to a blunt force trauma associated with a motor vehicle accident to compression from a tumor. It’s a good idea to have an understanding of the different ways a nerve can be injured. That way one can understand the prospects for recovery.
The first type of nerve injury is called a neurapraxia. In this injury the nerve itself maintains all of its internal connections. The anatomy of the inner nerve root is not altered and the injury simply represents a physiologic block of the nerve conduction.
Examples of a neurapraxic injury include having a tourniquet in place to stop bleeding. This may be during surgery or in a trauma situation to prevent too much blood loss. Having the tourniquet in place for too long may cause permanent injury to the peripheral nerves in the extremity. This is why surgeons often let down the extremity tourniquet every hour or so to let blood flow come back into the region and replenish the peripheral nerves.
Another type of neurapraxic injury is when an alcoholic passes out and sustains what’s called a “Saturday Night Palsy”. Normally as humans sleep they move around a lot. This prevents our nerve roots from being compressed in one position for too long. If a person is overly intoxicated he or she may not move around and end up with a compression injury, such as having an arm over a park bench and it being compressed consistently overnight.
As long as the neurapraxic injury has not been continuously in place for an extended period of time, there is potential for recovery, maybe even complete recovery. Out of the three types of nerve injuries, neurapraxia is typically the best for recovery since the anatomical structures are themselves intact.
The next category of a nerve injury is termed an axonotmesis. This injury represents an anatomical interruption of the internal peripheral nerve structures, the axons, however the connective tissue external framework remains predominantly intact.
This type of nerve injury requires significant regrowth of the axon, not just a “waking up” of the existing axon as with a neurapraxia. The axon needs to regrow along its path towards the target muscle it controls. In adults, this growth occurs at a rate of 1 inch monthly, or about 1 mm per day.
An example of an axonotmesis injury is in a car accident where the crush injury is more severe than a neuropraxia. The recovery possibilities are pretty good as the framework telling the axons where to go is intact.
The last type of nerve injury is the most severe and is termed neurotmesis. This occurs when there is actually a transection or disruption of the axon along with the connective tissue. A gunshot or knife injury may result in this injury. Early surgical treatment is typically recommended as spontaneous recovery is very unusual.