“I’d like to show my prowess, be a lion, not a mouwess, if I only had the nerve”
Cowardly Lion from “The Wizard of Oz”
It’s been a long sabbatical from the blog but I think I’ve come up with some new ideas to share. I’ll be trying to add a new topic each month and if there are any topics you would like to discuss please contact me at firstname.lastname@example.org and I will try to incorporate those into future posts.
One of the most serious injuries a person can suffer is a cut or laceration of a nerve to the hand or arm. Nerve injuries can be difficult to repair and the outcome of the surgery depends on a lot of factors, many of which are out of the control of either the patient or the surgeon. If you have had a laceration to a nerve I hope I can provide some information that will help you understand the injury and give you reasonable expectations about what can happen.
Nerves are probably the most complicated tissue in the body. The nervous system connects us with our environment and allows us to interact with the world. In the hand and upper extremity nerves have two main functions. First, they provide us with sensation so that we can feel the things we touch. Second, they power the muscles that allow us to move and manipulate our joints providing us the means to perform all the activities we want to do. These functions are intertwined, since optimal muscle function requires excellent sensation. Nerves also have a third function in that they control many autonomic (or automatic) functions of the hand such as sweating, hair growth and swelling.
The nerve itself is made up of nerve fibers that run from the hand to the spinal cord and then to the brain and back, and connective tissue that protects the nerve and gives the nerve some elasticity or the ability to stretch. Each nerve fiber runs through a connective tube that helps protect the nerve as well. In addition blood vessels run along the course of the nerve to supply nutrients to the nerve.
When a nerve is cut several things occur. First, because of the elasticity of the tissue the nerve ends always separate when they are cut. Second, the nerve reacts by basically trying to heal itself. Unfortunately since the nerve ends are never close enough together the nerve can’t heal itself unless it is put back together with surgery. If the nerve ends aren’t repaired the ends of the nerve will eventually form balls of scar tissue and nerve fibers that can be painful and sensitive.
Under ideal circumstances a nerve should be repaired within several days after injury. It is certainly not an emergency, but a delay beyond a week or two can effect the ability to repair the nerve end to end. The best injuries to repair are sharp lacerations that would occur by a knife. Less ideal are nerves cut by saw blades or nerves that separated during a crushing type injury.
Other structures are often injured along with the nerve. Tendons, bones, ligaments and skin and soft tissue injures can complicate the treatment plan. All things being equal and assuming that there are no other major complications, then nerve surgery has a very simple goal: to align the two nerve ends as close as possible. This is usually done with some very small suture that is probably about the size of a hair. Most of the time the best results are obtained when the surgeon uses and operating microscope, although this is not necessary. If there has been a delay in treating the injury, or if the nerve has been crushed or damaged to some degree, then a gap may develop between the two nerve ends. The surgeon may have to use a piece of nerve call a nerve graft to bridge the gap between the two ends of the nerve. After the surgery that arm usually has to be splinted for a period of time to allow the nerve ends to heal.
Once the nerve is repaired the healing process has only begun. It takes about a month for the ends of the nerve to heal, and then the nerve fibers start growing down the nerve through the tubules I described earlier. The goal of surgery is to get these tubules as close together as possible, but even the best nerve surgeon can only approximate the two ends of the nerve. The nerve doesn’t grow too fast, maybe an inch a month under the best circumstances. So you can see that if you cut a nerve near the elbow it may be two years or more before the nerve fibers could grow down to the hand.
There are several factors that affect nerve recovery. Age is the most important. The younger the patient the better the ability of the nerve to recover. I have seen some amazing results in children and young adults. However as we age the ability of our nerves to heal so that by the time we get older it’s difficult to get a nerve to heal well. The closer the nerve is to the place it’s trying to get, the better the result will be. A nerve cut in the finger has a better chance of recovering than a nerve cut in the wrist, for instance. Also, if the nerve has only one function (sensation or motor), then the chances of recovery are better. Some nerves have both motor and sensory functions and it’s harder to get all of those fibers lined up and headed in the right direction. Also, if all the tissues around the nerve are healthy the nerve has a better chance of recovering.
Given all these factors I see a wide variation in recovery after nerve surgery. I would recommend that if you have a choice of your surgeon try to choose someone who has experience in repairing nerves and is comfortable using a microscope. No nerve surgeon has perfect results but there is probably an advantage to having an experienced surgeon with these injuries.
I certainly hope you never have to deal with this type of injury but if you do I think the information I’ve provided can help you understand what you are dealing with.