If you lacerated your median nerve and have met with your surgeon and or occupational therapist, you have probably heard already that the median nerve will make a slower recovery than your tendons might. The reason for this is that tendons may be stretched and exercised whereas the nerve must regrow on its own. The median nerve regrows at a rate of one inch per month and grows from the site of laceration outwards, all the way up to the tips of your fingers. It is important to keep in mind also that the median nerve does not begin to regrow until approximately one month after it has been repaired. The rate of one inch per month begins one month after surgery. If you have injured your hand and have not seen a doctor yet but are wondering if you lacerated your median nerve, a quick way to tell is to feel the fingertips and look for both sensation and moisture. The skin naturally produces oils, although production will be stopped if the nerve is lacerated. As a result, all fingers affected by the median nerve laceration will feel dry compared to those not connected (the pinky and ring fingers).
Median Nerve Regrowth and Sensory Re-education:
Thenar Compartment Innervation:
The median nerve is not just responsible for sensation. This nerve breaks off into three branches, the first being the recurrent branch. This is an important branch because it is responsible for motor function in the thenar compartment. The thenar compartment consists of the opponens pollicis, abductor pollicis brevis, and the flexor pollicis brevis. For all intensive purposes, just consider this to be the group of muscles that control thumb movement. It is impossible to properly oppose or abduct the thumb without them, and therefore you will notice your ability to grip and hold items to be greatly compromised if your median nerve is lacerated. There are activities for exercising these muscles to help speed recovery and they can be found in the videos on the Timeline page. Ultimately, however, full mobility and sensation of the thumb will depend on full nerve regrowth and may take weeks to months depending on where the nerve was lacerated.
As you patiently wait for sensation to return to your fingers you may wonder how far along the nerve actually is in its regrowth. To answer this question, you may look for Tinel's sign. This can be found by lightly tapping the hand and looking for a pins and needles/electric feeling when you tap. If you experience these feelings, it is a sign that the nerve is still irritated and has not reached that point. If you tap and do not experience that sensation and discomfort, it means that your nerve has successfully regrown to that part of your hand. Rather intuitively, nerve regrowth is linear, not sporadic. After using Tinel's to determine to what point the nerve has recovered, measure the distance from that point to the site of laceration and remember that the nerve regrows at the rate of an inch a month; do these two match? If they do not then perhaps you have made a mistake, and you can double-check your method against this instructional video. Remember to use caution in performing this test though and do not use excessive force. Striking the nerve too hard could cause damage.
Understanding Sensory Re-education:
Sensory re-education is currently a developing field. The Department of Hand Surgery at the Malmo University Hospital in Sweden has published an interesting paper regarding this process, and the following information comes from that resource.
Nerve regrowth occurs at the rate of an inch per month, or 1mm per day. The Department of Hand Surgery breaks re-education into two phases with the first phase occurring after surgery. Your nerves are considered "silent" at first, and they are not providing feedback to the brain when you touch different objects. You cannot distinguish what you are touching even when looking at the object. The pathways for communicating your perception of touch in the fingers to the brain have been destroyed, and messages are not sent. Re-education begins in Phase 1. This period of re-education lasts the first 3 months post-op (for wrist level injuries) and consists of an individual touching objects while looking at them for several minutes at a time. This is to be repeated several times a day. This makes it easier for the pathways to form in Phase 2 after the axons have redeveloped. This training activates and trains a neurological map linking sensation in the fingers to response in the brain.
Phase 2 occurs when new axons begin to form and new pathways from the fingers to the brain begin to develop. They are in fact new pathways and therefore it takes time for them to grow and learn what textures provide certain feelings (you are not restoring old pathways). Through looking at different things as you touch them for extended periods of time, your brain will begin to recognize what these different things feel like. However, during Phase 2, you will need to lend visual support for your brain to help make the connection and relearn what different objects feel like. After approximately 3 months of phase one, the palm should begin to have slight sensation, and at this point training for Phase 2 may begin. The axons will then have reached the hand and the hand map should be established. It is now time to begin training the brain on what different textures feel like.